Dating Fender Tube
Amps by Serial Number, Part I
Copyright 1997, 20th Century Guitar Magazine.
Boy, that title got your attention didn't it? Well, we'll get to good parts, but first a little background information is in order. After reading Teagle and Sprung's excellent Fender amp book, I took them up on their challenge that maybe someday someone will compile enough serial numbers so that Fender amps can be dated that way. So began my quest. I contacted several Fenders collectors and dealers who were kind enough to supply me with data.
I turned to the Internet to do some more networking which resulted in a major turn of events as I met two individuals who have become instrumental partners in this project: Greg Huntington and Devin Riebe. Greg is a long time Fender collector who is very knowledgeable not only in the details, but in the circuitry as well. His particular area of expertise is in Fender amps made from about 1960 through 1967. Devin runs Doc's Music in Springfield, Missouri and his interest lies in the woodie and tweed Fender amps made from 1946 through 1960. Greg and Devin's experience meshed well with mine since I'm essentially the blackface/silverface amp guy (amps made between 1963 and 1980) in the group.
Additionally, Greg and Devin also had data that they had been collecting from Fender amps for years. We combined all of our information into a computerized database for this project and for the past 18 months have been slowly (sadly, very slowly) gathering information that we collect ourselves as well as from other people.
Now it's time for a commercial. We need your Fender amp data! Everything is confidential, we don't make record of who owns what amp in the database. What we need is the following:
1) Model name
One very interesting and very important factoid has surfaced regarding the date code letters on the tube chart. In the fall of 1965, Fender switched from stamping these numbers in black ink, to dark green ink. These 1965 codes begin with the letter "O." The code for the year 1966 is "P." However, someone in the factory apparently forgot to switch the stamper from "O" to "P" in January 1966. Therefore, amps from January 1966 have the date code "OA" (A denotes January) in green ink. The factory realized its mistake in February because these amps have a "PB" date code in black ink. Now, we obviously haven't looked at every amp made in January 1966 so this isn't set in stone. If anyone has an amp with a "PA" stamp, please let us know. Still, I wouldn't be too quick to just glance at that tube chart and accept an "OA" as a January 1965 amp.
The biggest tip off would be the control panels which brings us to interesting factoid #2. After CBS bought Fender in January 1965, there were still plenty of control panels for various models that were in stock. These say "Fender Electric Instruments." Depending on the model the use of these pre-CBS panels have been observed on amps as late as August 1965, except for Champs and Vibro Champs which had foil stickers on the back the chassis. Fender must have had a million of these labels printed up since they appear on Champs and Vibro Champs well into 1966. New panels made after the CBS acquisition were used beginning in April 1965 and say "Fender Musical Instruments." So, if you have January 1965 amp, it will have a Fender Electric Instruments panel whereas a January 1966 amp (even though it has that green "OA" date stamp) will have Fender Musical Instruments.
Okay, now on to the dating-by-number stuff. Although the database doesn't have thousands upon thousands of entries, we are seeing some interesting patterns emerging that will help date amps by serial number. Some of the trends are really obvious.
The early amps (woodie and tweed) had serial numbers handwritten on the tube chart. These appear to be used sequentially independent of model. Likewise, the brown/blonde Tremolux, Concert, Vibrasonic, Twin, Pro, Super, Vibrolux, Showman, Dual Showman, and Bandmaster used a sequential numbering independent of model, but as with Fender guitars, these were not used consecutively.
Some amps had their own numbering system. The 1956 to 1963 Champ, Harvard, Princeton, Deluxe; the 1956 to 1960 Vibrolux, the 1956 to 1964 Bassman, and all the tube reverb units have their own serialization scheme. The Champ has a "C" prefix, the Harvard an "H" prefix, the Princeton a "P" prefix, the Vibrolux a "F" prefix, and the Deluxe a "D" prefix. The 4x10 Bassman used the prefix "BM" while the piggyback Bassman used the prefix "BP." The reverb units have the prefix "R." In addition, the tweed Super, Pro and Bandmaster sometimes have the prefix "S" in the serial number.
The blackface and silverface amps (late 1963 to 1980) generally have serial numbers begin with the prefix "A." However, it appears that these were not used sequentially across all models. Our evidence is that we are finding some serial numbers duplicated between models. For example, serial number A00121 has been found on a Champ dated November 1964 and a Vibrolux Reverb dated February 1965. This makes things a little more interesting and difficult in playing the "dating game." And yet there is another variable to contend with as it appears that models that share chassis may also share the same serialization scheme. For instance, the Bandmaster Reverb and Super Reverb share the same chassis, and the Twin Reverb, Quad Reverb, Dual Showman Reverb, Vibrosonic Reverb, and Super Six all share the same chassis.
Preliminary results show that we're on the right track. Here's a couple of examples using the tweed Deluxe (model 5E3) and the Super Reverb/Bandmaster Reverb.
A27769 Super Reverb
So, with the knowledge gained thus far, we feel that Fender tube amps can be dated by serial number. We just don't have enough data to make any definitive conclusions yet. We will be writing articles in the future with more fun factoids (yes, there's more!) with new information on dating by serial number. Thanks for your support!
The author and his partners would like to thank those people who have sent us Fender amp information, especially James Werner, Tim Pershing, Gregg Hopkins at Vintage Amp Restoration, Jim Strahm and Matt Kesler at Midwestern Musical Co., and Tim Nelson at Mass Street Music. Also thanks to the many dealers at the various guitar shows that we visit for allowing us to make notes about the amps at their booths.
Dating Fender Tube Amps By Serial Number,
Copyright 1997, 20th Century Guitar Magazine.
It's been about 6 months since Part 1 of this series was printed so I thought it would be a good time to give an update on the Fender amp research that I am doing along with Devin Riebe and Greg Huntington. First I would like to thank everyone who responded to our request for data as outlined in the initial article that was printed in March 1997 issue of TCG. Most notably, I'd like to thank Jeff Lacio for his contributions to our research. Jeff is an amp tech who specializes in Fender amps, i.e. only Fender amps, and single handedly has submitted well over 250 very complete sets of data. Despite the heroic efforts by Jeff and other readers, we still need more data, so please keep it coming.
In the meantime, we have discovered many fascinating factoids about Fender amps and we'll probably learn a lot more as our research continues. Here are some examples of what we've found so far.
Early silver face amps: The silverface amps appear to have been introduced as early as April 1967 (yes, April!) and by the Fall of 1967 the conversion from blackface to silverface cosmetics was completed. The early silverface amps can be identified by the aluminum trim strip around the perimeter of the grill, the silver and blue grill, and black vertical lines silk-screened onto the front of the control panel.
The aluminum trim was retained through late 1969, though we speculate a few early 1970 amps may have had the grill trim as well. If anybody has a 1970 amp with trim please let us know! Two types of blue and silver grillcloth were used on the early silverface amps. The first type (1967 - early 1968) had no silver metallic threads and the second is the more familiar cloth with the silver metallic threads and a much greater texture or thickness than the first type (mid-1968 onward). The black vertical lines on the control panel were discontinued by May 1968 on most models, but we’ve seen a Bandmaster and Bassman from 1969 with them.
Interestingly, some silverface amps from early 1968 have 16 inch tilt back legs with serial numbers on one or both legs. Tilt back legs with serial numbers were used only on the speaker cabinets of piggyback amps. One of the legs on the cabinet would have the number while the other would simply be stamped with "Pat. Pend." In 1967, CBS Fender discontinued the small cabinet design Bassman and Bandmaster an introduced new, larger cabs without legs. Apparently, Fender had a surplus of 16 inch Bassman/Bandmaster tilt back legs with serial numbers on them. Rather than waste them, they were used on combo amps such as the Twin Reverb and Pro Reverb.
Although the cosmetics changed, the circuits remained unaltered from the blackface circuits on these early silverface amps. The date of the change from the blackface circuit to the CBS silverface circuit was dependent on the model, but most of the amps that were modified received the circuit change by mid-year of 1968.
Another interesting feature of the silverface amps is the change in chassis dates. Many blackface amps were stamped with a date code on the inside of the chassis. These read something like T020366 or F034267 where the "66" and "67" denote the year and the "03" and "42" denote week of the year. This system was continued on the silverface amps, some of which have the stamp on the underside of the chassis (where you can see it easily) in addition to the stamp on the chassis interior. This is very useful information in the absence of a tube chart or lack of a date code.
In the late 1970s and early 1980s, the chassis date stamp became more cryptic. For example, a chassis stamp of 1831 must be read backward to reveal the date, in this case week 13 of 1981. If you see a chassis stamp and you don't have any other dating info, please send it along with the serial number and model name to us, thanks!
Mistakes: Errors happen and Fender was not immune to them. Previously we discussed the "OA" date code stamped in dark green ink on January 1966 amps. The code should have been "PA," but the production staff forgot to change the year on the stamper. Well, I was contacted by one Chicago reader (I'm so embarrassed I forgot his name!) who has a February 1966 Deluxe Reverb stamped with "OB" in dark green ink (should be "PB"). This indicates that the production team didn't catch the error until early February 1966 at which time they switched from "O" to "P" and from dark green ink to black ink. Again, if you have an amp with an OA or OB date code you have to look at the front and back panels to see if it says Fender Electric Instruments (in which case the "O" denotes 1965) or Fender Musical Instruments (the "O" is a mistake and the amp is a '66).
And speaking of back panels... the back panel of our reader's Deluxe Reverb states "Division of Colombia Records Division" instead of "Division of Columbia Records Division." Note the spelling of Columbia has an "o" instead of a "u"!! At first this typographical error appears to have been short lived and confined to February 1966 since it hasn't been reported for any amps made in January or March 1966. However, just before this article went to print, I found a late 1965 Deluxe Reverb with Columbia misspelled. If you have an amp with this typographical error, please let us know and I'll report the results in Part 3 of this series!
And don't think that pre-CBS Fender was immune to mistakes... they weren't! I have seen two narrow panel tweed Deluxes from late 1957 with a misprint on the tube chart. Instead of showing the model number as "5E3" the tube chart was printed with "5F6." The 5F6 was the two input 4x10 Bassman, yet the tube chart is a Deluxe tube chart. Plausible reasons for this mistake making it into production: 1) Leo Fender, being frugal, may have use these erroneous tube charts just to save money, 2) the error wasn't noticed until a few dozen Deluxes were made, 3) there were no other tube charts available and Fender had no choice but to use the ones with the error until a new batch could be printed.
Another example of a mistake from the pre-CBS days is a brown '62 Concert amp that was mistakenly fitted with the circuit board from a blonde Twin/Showman! Oops!
Hole to Nowhere: Some of you may have noticed that the very early brown tolex amps from 1960 have a hole (sometimes plugged) on the back of the chassis labeled "Pulse Adjust." We have yet to find an amp with a potentiometer mounted there and no schematics that we have found to date show a "pulse adjust" pot. We speculate that Leo may have envisioned (and maybe even prototyped) a simple signal-injecting circuit whereby he planned to inject a pulse into the amp and adjust a control to optimize the amp's response to that pulse. This could have been a high frequency pulse and the amp's response could have been adjusted to yield the best high frequency reproduction just short of allowing a high frequency parasitic oscillation.
Or... it could have involved injecting a high level pulse and the control was adjusted to optimize the amp's response to obtain the best (balanced) sine wave with minimum crossover. Or... it could have involved injecting a "square wave" and the control was adjusted to obtain the best non-ringing, non-sagging waveform. Or... it could simply have been a bias adjustment. Despite all the theory and conjecture, Fender clearly deemed the Pulse Adjust control to be unnecessary.
First, Last and Transitional: During our research, we do find some amps that are especially interesting because they are one of the first, one of the last, or a transitional example of a particular model made. For instance, we found a very early Quadreverb (s/n A38053). This model was introduced in 1972 and this particular amp had transformers and speakers dated from late 1971, though it was probably assembled in the very early part of 1972.
The Tremolux (AB763) and Reverb Unit (6G15) were both discontinued in 1966. In fact, Greg Huntington has a Fender catalog dated September 16, 1966 and it does not list the Tremolux. The latest Tremolux that we have in the database (s/n A07779) hails from September 1966 and has a production number of 71. We also have two others from this same production batch with September 1966 tube chart dates so it looks like this was the last month of production for the venerable Tremolux. The latest Reverb Unit that we have seen (s/n R10651) is from May 1966 with a production number of 46. However, we aren't sure at this point if May is the last month of production for the tube reverb unit. If you have a later example, please let us know!
An example of a transitional amp is the first batch of blackface Dual Showmans (AA763). These are very rare and are prized more by collectors than players. The blackface Dual Showman circuit was introduced in September 1963. The amps were covered in smooth blond tolex and had tan/gold grill cloth. The very first batches of these amps (Prod. #2 for sure, but likely Prod. #1 as well) from September and October 1963 used a quad of 7355 power tubes instead of 6L6GCs as the blonde Dual Showman (6G14-A) and most blackface Dual Showman (AB763). This amp uses a completely unique output transformer (Part # 125A18A) not found on any other amp though there is speculation and some evidence that a few of the very earliest Twin Reverbs used 7355s since, like the Dual Showman, it was an 80 watt, 4 power tube amp with a 4 ohm output transformer. In addition, the 1963 catalog specifically shows 7355 power tubes for the Twin, Showman and.... the Bassman and possibly the Concert!
Though we don't know why 7355s were used, perhaps Leo got a good deal from RCA on a boatload of these tubes so he tried them out in the Dual Showman and Twin Reverb. So why did he switch back to 6L6GCs? Probably because the 7355s aren't rated to operate at the higher voltages that the Dual Showman and Twin Reverb could dish out. They are a smaller tube, similar to a 5881/6L6GB and hence can get hotter than a tube with a larger envelope. By all accounts from two owners of Dual Showman with 7355s, they don't produce as much power as a Twin Reverb or Dual Showman with 6L6GCs, though the tone is apparently acceptable. These days 7355s aren't too easy to find either. Hence, these are reasons why players don't care about these rarebirds very much and have converted some of them to use 6L6GCs. Debauchery!
Dating by Serial Number: Here's the part everyone has been waiting for. Yes, we are confident that we have cracked the date codes on the reissue amps! We have some transformer date code information to support this, too. There are two letters stamped on the tube chart on the line that says "Production." The first letter denotes the year and the second letter denotes the month just like on the amps made in the '50s and '60s. However, the reissue codes are as follows:
A = 1990 A = January
For example, reissue Bassman (s/n AA05559) with the Production Code EJ would have a production date of October 1994.
Unfortunately, for the older amps, we still are not at the
point where we can give any kind of definitive dating scheme. To satisfy
your thirst for knowledge, here's another sample from the database that
shows that we are on the right track, but that we desperately need more data
A20599 Princeton Reverb 1968
As you can see, we do get quite a bit of data without any date code info which create "holes" in the database. This is problematic, but lately folks are feeling more comfortable finding the transformer date codes and sending them to us with the serial number/model name for their silverface amps.
Reminder: We are still in need of information about
any and all Fender tube amps. Everything is confidential, we don't make
record of who owns what amp in the database. What we need is the following
So please... use the hand form mentioned above, or send your
amp data to the author c/o TCG Magazine or by e-mail to
email@example.com. Thanks for
your support and stay tuned for Part 3 of this series!
The author and his partners would like to thank those people who have sent us Fender amp information (and you know who you are dahlings). Also thanks to the many dealers at the various guitar shows that we visit for allowing us to make notes about the amps at their booths.
Dating Fender Tube Amps by Serial Number,
Copyright 1999, 20th Century Guitar Magazine.
I know, I know. It’s been over a year since Part 2 of this series was printed, but that’s because I’ve been busy collecting data. For those readers who may have joined us recently, I am doing some Fender amp research along with Devin Riebe and Greg Huntington. Our research efforts are now in their fourth year (will it ever end?). Part 1 and Part 2 of this series can be found in the March 1997 and November 1997 issues of TCG, respectively.
Again, I would like to thank everyone who responded to our request for data as outlined in Parts 1 and 2.
The main focus of this article will be speakers found in Fender amps, but before we get into that topic let's go over a few other areas first.
Early silver face amps: Part 2 went into this topic in some detail, but since that article was printed, I have been asked a lot of questions about this subject. There still seems to be some confusion about how to distinguish between a silverface Fender amp that has the desirable AB763 circuit and one that has the less-desirable AB568/AC568 circuit. Part of the confusion stems from the lack of any AB568 or AC568 tube charts. Fender never printed any since there were plenty of leftover AB763 tube charts available and these were used well into 1969.
Although the cosmetics changed, the circuits remained unaltered from the blackface circuits on the earliest silverface amps. The date of the change from the blackface circuit to the CBS silverface circuit was dependent on the model, but most of the amps that were modified received the circuit change by mid-year of 1968.
The cosmetics of the silverface amps during the transition between circuits was also in transition making it difficult to determine circuit type on cosmetics alone. The amps during this period could have the earliest style silverface grill cloth or the more familiar silverface grill cloth. All of the amps would have the aluminum grill trim and they may or may not have the thin black vertical lines on the control panel. One clue that can be used is the ink stamped chassis date code that is usually located in the chassis, but is sometimes found on the underside of the chassis behind the tubes. These read something like T020366 or F034267 where the "66" and "67" denote the year and the "03" and "42" denote week of the year.
Of course, the most foolproof way is to pull the chassis and look at the layout. In fact, on the 40-watt and 80-watt amps you can simply pull the chassis out about 2 inches and look for the big honking ceramic power resistors that are connected to ground from the cathode (pin 8) of the power tubes. If those resistors are there, the amp has the dreaded CBS silverface circuit. I am also confident that the serial number can be used as a rough guide for determining the circuit, but again, pulling the chassis is the only way to confirm.
Transitional circuits: I've been getting quite a few reports from amp geeks about circuits that don't completely match the schematic for a particular model. Leo Fender was notorious for tweaking circuits and the results of some of his tinkering can be found on late examples of an amp prior to the switch to a new circuit. Also, the different component values could be due to a necessary substitution on the production line when a particular value was out of stock. Ran out of 100K ohm resistors? Stick a 90K in there: no one will notice or care (at least not until the mid to late 1990s).
These changes have been observed on tweed, brown/blonde, and blackface models. Often the differences are minor such as small changes in resistor or capacitor values. I had a '63 Concert with the 6G12-A circuit but had a completely different (factory stock) bias supply circuit than shown on the schematic.
Perhaps the most surprising transitional circuit that has been reported to me (thanks Brian!) is for the early 1968 silverface Showman. Two examples are known to exist; one from the February-March period and one from the March-April period. These amps have AB763 tube charts and normally any silverface amp made prior to May 1968 will have the AB763 (a.k.a. blackface) circuit. After April 1968, most of the big Fender amps received the AC568 circuit, which is a semi-cathode biased design. However, these two Showman amps have a fully cathode biased design that is factory stock!!! There is also an unconfirmed report of an early '68 Twin Reverb with the cathode bias circuit. If you see one of these cathode biased amps, please let me know!
These amps do not have a bias trim pot. The wire from the two 220K ohm bias resistors is connected to the brass control panel ground plate. The only thing connected to the bias cap/diode is the tremolo circuit. The cathodes are tied together and connected to a single 165-ohm resistor and 80 mfd 150V bypass capacitor which are both grounded at the other end. This cathode set up is similar to, but simpler than, the AC568 circuit. Every other part of the circuit (power and preamp) is identical to the blackface AB763 schematic.
Perhaps these two Showman amps were field prototypes, experimental units, transitional between the AB763 and AC563 circuit, or just a plain bad idea. Bad because cathode biased amps run very hot especially those with four power tubes (witness the Vox AC-30). In addition, a cathode biased Showman would produce something around 50 watts of power instead of the 80-plus watts from a fixed (grid) bias Showman. According to the owner of one of the cathode biased amps, it runs very hot; so hot that the tolex melted under the chassis mounting strap near the power tubes! Also, the amp eats power tubes, does not have much headroom and breaks up early.
Oddities: One of Leo's experiments or "one off" custom amps surfaced recently. It's a circa 1955 tweed Tremolux (5E9) that has two factory stock Jensen Hi-Frequency tweeters with a passive crossover between the Jensen P12R and the tweeters. I wonder if Leo was influenced by Magnatone's use of tweeters?
A few export model brown/blonde amps have surfaced that have a 6-way voltage selector switch located in the chassis, instead of on the back of the chassis. This necessitates removing the chassis from the cab to change the voltage setting (which would only be a problem if you hopping from country to country with the amp). Interestingly, these amps have Triad power transformers while concurrently produced domestic models had Schumacher units.
CBS era quality control: We've previously discussed the "OA" and "OB" date codes mistakenly stamped on the tube charts of January 1966 and February 1966 amps, respectively. As well, we've discussed misspelling "Division of Colombia Records Division" instead of "Division of Columbia Records Division" on the rear chassis panel on some amps from late 1965 and early 1966.
These mistakes were merely cosmetic. There were quality lapses in the circuits themselves during the CBS years, some of which had serious consequences. Examples of these include ceramic caps used in parallel to achieve the correct value instead of a single cap, change to often inferior sounding "chocolate drop" caps, and incorrectly wired circuits.
A friend brought me a '66 Princeton Reverb that was humming badly. I recognized the 60 cycle hum and thought perhaps the filter caps were shot, but it turned out the two 100-ohm ground resistors for the tube filaments were never installed at the factory!!! I’m surprised the Fender dealer didn't send the amp back and even more surprised that somebody bought it with the way it was humming!
I also worked on a late '67 silverface Deluxe Reverb (with the blackface circuit) with an inoperable tremolo. Boy, was I surprised to see that the tremolo circuit was wired incorrectly by the factory!!! Either the factory worker was asleep at the wheel that day or there was a new hire that was still learning how to assemble amplifier circuit boards. I tend to believe that the latter idea has some merit since Fender practically doubled its size after the CBS takeover. Bigger facilities meant more workers with little or no experience.
Speakers: Like many people, I was a bit disappointed that Teagle and Sprung's Fender amp book did not have much info on speakers. So, I have compiled a list of speakers used in Fender amps and took some photos of some of them as well. The list, presented below, is based on our actual observations, but is not comprehensive. If you have a Fender amp with a factory stock speaker other than one shown here, please let us know and we'll add it to the list!
JBL: JBL speakers were optional (at additional cost) for nearly all models from 1960 to about 1980. JBL D-series speakers had orange baskets and Fender by JBL labels in the 1970s. JBL D-series speakers can generally handle upwards of 60 watts each. A pair of JBL D-120Fs in a Twin Reverb are only seeing about 40-watts each (no sweat), but remember that no speaker likes to see square waveforms. So, driving the Twin with any amount of distortion lowers the power handling capacity of the speaker, which makes any speaker more susceptible to damage; even a high-wattage type like the JBL.
Jensen: Jensen was the prevalent stock speaker in Fender amps from 1946 through about 1961. As the story goes, Leo Fender wanted Jensen to make some changes to speakers and either the speaker couldn't (price constraints?) or wouldn't do so. That's when ol' Leo switched over to Oxford as the standard speaker (though Jensens were still used from time to time). Just conjecture, but the lack of orders from Fender from 1962 - 65 must have hurt Jensen's pocketbook so they hit up the new owners of Fender (CBS) for some business. These Jensens wear brown and gold Fender by Jensen label and were put into Fender amps beginning in late 1965 through about mid-1967. Some amp geeks don't like the way these Fender label Jensens sound, but let your ears be your guide. I think they sound just spiffy.
Jensen Vibranto LI and MI series speakers (alnico magnets) and Jensen EM-series speakers (ceramic magnets), while excellent, were not used by Fender. I have included them here because I get a lot of questions about them. They are were often sold as replacements for blown speakers which is probably one reason why the ended up in more than a few Fenders. The Vibranto LI series speakers had a lifetime warranty and it seems that Jensen went out of the musical instrument speaker business just in time to avoid the claims. All speakers can and will fail eventually (just like the hard disk on your computer); remember that.
Jensen speaker models denote their approximate power handling capacity and magnet type. The actual power ratings have been published in several books so I'll discuss them in general terms here.
The R, S, and T suffixes denote a low power rating: good for Princetons and Champs, but the R is barely able to handle the power of a Deluxe. The Q and P suffixes denote a medium power rating. These are especially good for multi-speaker amps up to 40-watts since multiple speakers divide the amp's total output power between them. For this reason, the P10Q is the speaker to have in the 5F6-A Bassman. Note that it does not appear that Fender used the "P" rated speakers very often. The N and LL suffixes denote a high power rating, with "high power" being a relative term. The P12N, on a good day, can handle 20 watts. It's no wonder that 80-watt Twins easily shredded a pair of them. Note that Fender did not use the "L" rated speakers (but Ampeg and Leslie did).
Oxford: Oxford speakers codes work in a similar fashion, but it is the letter that denotes power handling. The higher the letter, the higher the power rating. I found an Oxford ad in a 1960s trade magazine with the peak power ratings of some speakers: K = 25 watts, L = 30 watts, M = 40 watts, and T = 45 watts (12" speaker) or 60 watts (15" speaker). It is important to note that these are peak power ratings, not RMS power. The RMS rating is more realistic and is usually about half of the peak rating so use that as a rough guide.
The "J" rated speakers are usually found on 12-watt Princetons. The "K" rated speakers are found in reverb and non-reverb Deluxes and in multi-speaker amps up to 40-watts such as the Tremolux and Concert. The "L" rated speakers are found in reverb and non-reverb Deluxes, some Tremolux amps, and multi-speaker amps like the blackface Concert, Super Reverb and Vibrolux Reverb. The "M" rated speakers had good service life in the piggyback Bassman and Bandmaster amps, but were easily blown in blonde Twins. The "T" rated speakers were standard in Twin Reverbs, but like the Jensen C12Ns, they often had a short service life.
Many amp geeks don't like Oxford speakers found in Fender amps from 1965 through the 1970s. The gap distance was increased in the Oxfords that Fender used later in the decade and this reduced their efficiency (and they were cheaper to make this way). Again, I say let your ears be your guide. I've heard many great sounding Fender amps with Oxfords. I will admit that I prefer Jensens, but I've never let an Oxford speaker sway my decision from owning a Fender amp. Additionally, the Oxfords from early '60s generally sound very good. According to noted vintage amp specialist Gregg Hopkins, these early Oxfords were constructed similarly to Jensens from that period with respect to materials and voice coil gap. That could explain why they sound good.
CTS: CTS (Chicago Telephone Supply!) speakers were used occasionally in Fender amps until the mid-1960s. These are good quality speakers that tonally lie between Jensens and Oxfords. The alnico 10-inch CTS speaker was the most prevalent speaker in Super Reverbs from the mid-1960s through the 1970s.
Utah: Fender didn't use Utah speakers very much until the 1970s. The Utah speakers from the '50s sound very good and I've heard a killer '66 Super Reverb that was equipped with factory original Utahs. Generally, the Utah speakers of the '70s weren't as great sounding as their predecessors, but again let your ears be your guide. If you like the way your '75 Twin Reverb sounds with its Utah speakers, just leave it alone and go right on playing. Utah went on to become Pyle of Radio Shack and car audio fame.
Eminence: Eminence has its roots in CTS (Mr. Gault left CTS to found Eminence) and many of the early Eminence designs are similar or identical to CTS speakers (good examples of the similarities can be found in mid-1970s Ampegs). Fender began using Eminence speakers as standard in nearly all of its tube amps beginning in the early 1980s. These are generally made to Fender's specifications and in some cases, such as the reissue '65 Twin Reverb, the speakers were designed to emulate the Jensen C12N speakers which were often found in the original '65 Twin.
Rola: Yet another speaker that Fender used in the mid to late 1970s was Rola.
So in technical terms, why don't the non-Jensen speakers from the mid-1960s through the 1970s sound as good as Jensen speakers? Speaker guru Ted Weber explains:
"Utah, CTS, Oxford, etc. simply copied the Jensen designs and started competing for Fender's business. As a result of the price wars, they had figure out how to make the speakers produceable with a very low reject rate as well as use less expensive parts, i.e. smaller magnets. So, they widened the gaps to make them easier to throw together on a fast assembly line. This lowered the energy, so the voice coils were shortened to compensate. The companies also needed to produce speakers with long term reliability, so they doped the surrounds. The end result is that with some of these speakers you get a relatively sensitive driver that sounds great at lower volumes, but falls apart when you push it -- flabby on the low end and/or harsh on the high end."
Replacement speakers: It is very common to find non-original speakers in Fender amps made up through about 1980. Because reconing wasn't a common option until the 1970s, players simply replaced the speakers if they blew up. In some cases, such as Altec and JBL, the factory would recone a speaker. Today, reconing is a very popular option for players to keep their amp's speakers original. Reconing must be done correctly and with the right parts so stick with a reputable reconing service that offers a warranty. In most cases, the reconed speaker will sound nearly as good or as good as the original. In some cases, the speaker will sound even better. The reconed Oxford 12K5 in my Deluxe Reverb sounds better than any original cone 12K5 I've heard.
There is a strong market for used speakers. Many times a player can find an original speaker to replace the non-original speaker. Another option is to install vintage style speakers. Jensen has reissued the C10Q, P10R and P12N and WeberVST makes many models of Jensen-style alnico and ceramic speakers.
One final note before you scope out the speaker chart --
there are exceptions to every rule and this especially applies to Fender!
So, if you see a factory stock P12P in a tweed Deluxe, don't be overly
A New Internet Resource: Over the last 12 months or so, I've had several people ask me to put together some sort of Fender amp guide on my web site. A great idea, but I simply didn't (and still don't) have time for such a venture. However, Mark Ware thought it was a good idea, too, and he put together a very informative Fender Amp Field Guide. The site is nicely done and includes descriptions, pictures, and schematics for Fender tube amps as well as other Fendercentric information.
Dating by Serial Number Update: The good news is that good progress is being made, but I am in fact, still desperate (if you could only see the pitiful look on my face right now) for more info, especially for tweed, brown, blonde and silverface amps. I have practically no information for some models like the Bassman 100 and other "non-popular" silverface amps. And keep those blackface amp data coming! Also, I need more information from reissue '63 Vibroverb amps and Custom Vibrolux Reverb amps.
I'm still trying to make sense of the "mysterious" production numbers and this is one area where I don't have a lot of info: mainly because production numbers were not written on a lot of the tube charts. However, the next article in this series (Part 4) will discuss some preliminary production trends (oh boy!). Were 1,000 or 10,000 or 100,000 Super Reverbs made? Stay tuned.
Reminder: We are still in need of information about any and all Fender tube amps. Everything is confidential, we don't make record of who owns what amp in the database. What we need is the following:
1) Model name
2) Model number on the tube chart
3) Date code letters on the tube chart
4) Production number on the tube chart
5) Speaker codes and model (if speaker is original)
6) Transformer codes (if the amp doesn't have date codes on the tube chart)
7) Cosmetic features (flat/raised logo, tweed/tolex, blackface/silverface, rough/
smooth blond tolex, white/skirted knobs, TV-front/wide-panel, etc.)
So please... send your amp data to the author c/o TCG Magazine. Thanks for your support and stay tuned for Part 4 of this series!
Special thanks to Gregg Hopkins at Vintage Amp Restoration, St. Louis, Missouri for allowing me to photograph the speakers from his inventory.
The author and his partners would like to thank those people who have sent us Fender amp information (and you know who you are dahlings). Also thanks to the many dealers that we visit for allowing us to make notes about the amps in their shops and at their guitar show booths.
DATING FENDER AMPS BY SERIAL NUMBER, PART IV
Copyright 2001, 20th Century
Yes, I know it's been exactly two years since the last installment in this series. Before we get into the amp info, let me give you an update on what's been going on since I've been getting a lot of e-mail asking when the results of the research is going to be available.
First, we (Devin Riebe, Greg Huntington and myself) must collect enough information to be able to date amps by serial and determine production totals. "Enough" means an adequate amount of information to identify trends with reasonable certainty. Sadly, the majority of information we gather does not have any details about possible date of manufacture (pot dates, transformer dates, tube chart date codes, etc.) and without this important info, the research takes longer.
Second, we are very dependent on information sharing. Devin, Greg and I do collect data on our own, but the research goes much more quickly when we receive information from other sources, i.e. other people. And it's not always easy to collect data ourselves. Some stores and dealers at guitar shows are very happy to let use inspect their amps while others go ballistic and show us the door. Some collectors send information, others, upon first contact, run away to their secret underground amp lairs never to be heard from again. But we persevere through thick and thin.
This brings us to another topic which I will briefly mention. Many, many nice people from the United States, Canada, South America, Europe, Australia, New Zealand, and Japan have contributed information to our research and we are extremely grateful to all of you (and you know who you are dah'lings). I try my best to answer each and every e-mail that I receive that either requests information or that submits info for our research. Sometimes my answers are very short, but that's usually because I have a lot of other e-mail to read and answer. It's not because I'm trying to brush any one aside.
Occasionally, we have to deal with mean people who do not wish to contribute data as they feel our research is a one-way street. Honestly, I don't understand why they the bother writing if they don't want to contribute. Just don't contact us, it's that easy, sheesh. I find their rhetoric tiresome, but as the authors of the Ampeg book and I discovered during our Ampeg research, mean people are just part of the game. Ironically, it's the mean people who most often ask to see our results: a one-way street, their way! Thankfully, the nice people far outnumber the mean people and I again want to thank all the nice people for their support and encouragement as well as for the information they provide.
Third, this is hard work. I could probably earn a Ph.D. from this project. Sometimes we need to take a break and taking a break means not making any progress. We don't get paid for this and we all have day jobs. This is a hobby for us and a labor of love, or insanity, take your pick.
Lastly, during the course of our studies we've come across several complicating factors that have slowed things up. We're are more frequently encountering "parts amps". As with vintage Fender guitars, Fender amps (which have lots of bolt-on parts) are being modified to make a less desirable amp (silverface) into s more desirable one (blackface). Most of this are really easy to spot, but we still have to weed through this "parts amps" to figure out what they are or aren't (be careful out there!). As mentioned in previous installments in this series, the majority of Fender amps are serialized by model and/or chassis type. Many of these serialization schemes changed within a given model. Also, there is some duplication of serial numbers for a given model. I will go into the details of the serial number systems in the next article, but needless to say, it makes thing much more difficult for us.
If you would like to contribute information to our research you can do so by e-mail (firstname.lastname@example.org). All the info is entered anonymously and we don't keep records of who sent what info.
Also please note, thanks to Mr. Gearhead (see below), we are no longer collecting data for any Fender tube amp made after 1984, except Reissue models (we still want info for those!). Solid state amps were, and still remain, excluded from our research. That means we don't need info for models such as The Twin, Pro Jr., Blues Deluxe, Sedan deVille, etc. But we do want info for the '59 Bassman, '63 Vibroverb, '65 Twin Reverb, '65 Deluxe Reverb, '63 Reverb Unit, Custom Vibrolux Reverb (not a true reissue, but what the heck, we dig it) and the newly released '65 Super Reverb. Call us vintage snobs, but we gotta draw the line somewhere.
For those of you with "modern" Fender amps (tube or solid state made after 1989) or Fender reissue amps, you can go to FMIC's "Mr. Gearhead" web site (www.mrgearhead.net) which now explains how to date these amps based on codes and serial numbers. We cracked the reissue amp code here first (kudos to us, see TCG Nov. 1997), but the Mr. Gearhead site is very convenient.
Now that we're up to date, let me pass along some interesting tidbits of info that have surfaced in the last year or so.
There are some silverface Twin Reverbs from circa 1970 and Vibro Champs from circa 1973 without an "A" prefix in the serial number (I hate when that happens). Several Twin Reverbs from late 1971 (specifically October) have been observed with master volume chassis holes, but with conventional faceplates. This would indicate that FMI was already thinking about the change to the master volume circuit in Fall 1971 and probably even earlier.
Regarding model numbers, the model number for the Super Six Reverb is CFA7106 and the model number for the Quad Reverb is CFA7104. It appears that the last digit refers to the number of speakers. Since these model numbers are for the master volume models which shared the same chassis and circuit as the master volume Twin Reverb, I have to wonder if the model number for the master volume Twin (2x12) would be CFA7102 and the Vibrosonic Reverb (1x15) would be CFA7101. I haven't yet found the model numbers for these amps with the ultralinear circuit. The "D" suffix in the model numbers for the Dual Showman Reverb (TFL5000D) and Bandmaster Reverb (TFL5005D) denotes an amp for Domestic sale. Those with an "X" suffix, such as TFL5005X, were for eXport sale.
And speaking of export amps, I have several reports from Sweden that Fender export models from that country do not have the usual multitap power transformer with selector switch on the back of the chassis. Rather they are hardwired for 220V to meet the Swedish equivalent of U.L. approval. Another interesting tidbit is that Fender amps may have been distributed in Sweden by Hagstrom.
One frequently asked question I receive is "What is the
difference between the AA763 and AB763 circuit for a Super Reverb (or Twin
Reverb or Deluxe Reverb)?" For those without access to schematics, here are
The most important difference is the addition of the grid stoppers (safety first!). The only major difference in tone between the two circuits would be attributable to the different tone caps (.033 vs. .047). The .033 cap would yield slightly more midrange, but I don't think it would be very noticeable.
For some models like the blackface Concert, there was no change in phase-inverter resistor values, and no changes in tone stack cap values (fascinating!). And for other models, the tone stack did not change from .033 to .047 uf, but rather from .033 to .022 uf. The Bandmasters also saw no change in tone stack cap values between the AA763 and AB763 circuits. The "universal" changes do seem to be the oscillator circuit, cathode resistor change from 56K to 100K, and the addition of the 1500-ohm grid stopper resistors.
Did you know that early blackface amps (1963) do not have white silk screening around the bright switches? It's not certain when Fender added the white rectangle around the bright switches, but they are there by early 1964. Whether this was added before the end of 1963 is not known (yet). This feature would have been phased-in at slightly different times for the different amps as faceplates were ordered and used in somewhat different amounts and at somewhat different rates for each model.
Some general information about cabinet construction: solid pine, finger-joined cabinet construction from 1946 to circa 1972. An interesting feature on the tweed-style cabinets is the use of a dowel reinforcement in the top on either side of chassis. You can't see the dowels unless the tweed covering is removed, but this reinforcement prevented the wood from splitting due to the weight of the chassis.
Baffle boards were made of plywood from 1946 to 1962. Particle board (some call it MDF - medium density fiberboard) baffles debuted in 1963 and were used through the early 1980s. The baffle board was removable on amps made from 1948 to about 1972 and glued-in thereafter.
From circa 1972 to the early 1980s, the cabinets were no longer made from solid pine boards, but cheaper laminated, multi-piece pine boards. Each side of the cabinet was made from several pieces about three or four inches wide, glued side-to-side, to make up a plank the depth of the cabinet. These laminated cabs were not finger joined, but rabbet joined. The baffle board on these rabbet joined cabinets was mortised into the sides and bottom (i.e. not removable) to hold the whole thing together. That's why these post-1972 cabinets have the grill cloth stretched across a frame that is attached by a velcro-like system to the baffle. CBS almost certainly went to this construction method to save money, though at the expense of overall quality.
And with Fender, there are always exceptions to the rule. I have received reports of some pre-CBS blackface amps with one or more sides made from a multi-piece board. As well, I have received reports of some particle board bottoms used in master volume-era silverface amps.
I'm often asked if the marking on the inside of the cabinets are date codes. Sometimes date codes are ink stamped on the inside of the cabinet (mainly blackface and silverface amps including the piggyback speaker cabs), but those handwritten numbers you see in wax pencil or lumber crayon are actually matching marks. As a worker would through a run of cabinets and fit baffles to each one, he would mark the cab and baffle so they could be "married up" again after the baffle was grilled. The cabs were probably numbered sequentially within the production run. The number did not have any relationship to a particular employee though Sam Hutton is known to have marked the cabinets he assembled (usually in yellow lumber crayon) with an "S" superimposed over an "H" which looks like a $ with two strikes instead of one.
We've received some interesting reports about some oddball amps. The first was a 1960 brown Super Amp. The latest date code on it indicated 30th week of 1960 and the circuit and layout were neither 6G4 nor 6G4-A. This must have been one of those "Leo messed with it" amps that Forrest White speaks of in his book. This circuit is unique and transitional - part 6G4 in places, part 6G4-A in places, part "unique experimentation" in places.
An October 1963 Deluxe Reverb was reported with transformers (all Schumacher) all dated to mid-1963, except the reverb drive transformer which dated to December 62! The tube chart indicated the AA763 circuit, but there were some very strange original resistor values inside. Specifically, the reverb drive tube's cathode bias resistor was a 1K, 1-watt, instead of the normal 2.2K, ½-watt. The tail resistor in the phase inverter was 6.8K, the plate load resistors in the phase inverter were 47K and 56K instead of the normal (for AA763) 100K. The bias feed resistors were 68K instead of the normal 220K, and there was a disc ceramic cap on the board connected between the phase inverter plates. The ceramic cap is more commonly found on brown and blonde amps to prevent parasitic oscillation.
Some amp techs have observed examples of blonde and blackface amps with power transformers without center-tapped filament windings. These amps are usually the ones that have "hum" problems if they don't have 100-filament resistors added. Somewhere along the line Fender went to a center-tapped filament winding and no 100-ohm filament resistors. These amps could be modified simply by lifting the center tap, and installing the 100-ohm resistors in the usual place on the power lamp socket. If a filament in a tube shorts (happens most often in power tubes) it is a lot cheaper to replace a 10-cent resistor or two, than an $100 power transformer.
Fender's sudden transition from cloth wire to thick PVC wire (in pastel greens, white & yellows) is well documented by anyone who has ever pulled a chassis. Sometime in late 1968, the cloth covered wire went away. However, several amps from the late '60s (non-reverb Princeton, Vibrolux Reverb, Bandmaster Reverb, and possibly a Deluxe Reverb) with oddball wire have been reported. The Princeton Amp was an early-mid 1969 model entirely wired (factory original & stock) with thinwall, 22awg irradiated PVC (IPVC) wiring. IPVC wiring is usually found in electronics like computers, not lo-fi amps. Keep your eyes peeled for wire with very thin, cream to yellow insulation. It's likely IPVC.
Scanning a few internet discussion pages, I've noticed quite a bit of misinformation going around regarding Fender tube amps mainly from people who haven't studied the available published literature on Fender amps, i.e. they haven't been reading these articles in TCG. The good thing is that the misinformation is often corrected by someone who is knowledgeable. One of the most common topics that falls into this category is early silverface amps. Here's a very quick summary that may be helpful: the earliest silverface amps were made in 1967 not 1968, not all "drip edge" silverface amps are from 1968 or 1969 (they could be from 1967), not all "black line" drip edge silverface amps have the blackface circuit except for Vibrolux Reverbs, Deluxe Reverbs, Princetons, Princeton Reverbs, Champs, Vibro Champs, and Broncos.
I'll leave you with a bit of juicy info, namely, some preliminary production estimates for several random amp models. This info will be further refined and presented in a future article (and y' all can hardly wait, I know).
Bassman (blonde) 12,000 units
Princeton Reverb (blackface) 19,000 units
Tremolux (blackface) 8,000 units
Vibrolux Reverb (blackface) 10,000 units
Vibroverb (reissue) 6,000 units
Special thanks to amp tech guru and fellow Jersey Boy, Mark Norwine at Carlson Amplification Inc., and Gregg "Portaflex" Hopkins at Vintage Amp Restoration for contributing interesting and fun facts to this series.
DATING FENDER AMPS BY SERIAL NUMBER, PART V
20th Century Guitar Magazine
They said it couldn't be done!
Okay, I know you're all just dying to skip ahead to the serial number tables but try to contain your excitement and read through the article first. I promise the tables will still be there after you finish reading. Besides, no article in the Dating Fender Amps by Serial Number series would be complete without some interesting information, n'est ce pas?
Non-Schumacher transformers - It's been universally accepted that Fender only used Schumacher transformers on amps made in the 1960s and 1970s. These are marked with EIA code "606" which is the company number for Schumacher. Well, this universal "truth" was debunked when we found a bunch of amps with transformers made by the Better Coil and Transformers company. These are marked with EIA code "831" and are most prevalent during the 1966-68 time period. Some examples include a '66 Princeton Reverb and '6 Pro Reverb with Better Coil output transformer, a '66 Deluxe Reverb and '67 Twin Reverb with Better Coil reverb transformer, and a 1968 Vibro Champ with Better Coil trannies. These units look, and apparently sound, just like the Schumacher-made units so it's easy to overlook that "831" code.
Working at FMI - I was able to interview a fellow (who wishes to remain anonymous) who worked at Fender in 1972-73 in the amp department. Although his job was somewhat limited, his recollections provided some really fascinating insights to how the amps were built. For instance, he confirmed our assumption that the amp chassis were put into stock after being stamped with serial numbers and that the chassis were pulled from the stock bins randomly (just as with Fender guitar neck plates). He recalled, "We just went to a big bin every morning and loaded our wheeled rack with a batch of whatever chassis we were working on that day. The boss came around and said what we'd be building. The chassis weren't used chronologically. Probably the same as the pots and transformers that we just dug out of the boxes. I think in the corners of the boxes were older pots remaining from earlier dates... leftovers."
Regarding production he recounted the following
information: "I think I remember being 'pushed' to come up with 30 of the
simpler chassis (Super Reverb?) per day. I think the better, older hands
did 35 a day. Like I said, there were 5 or 6 of us at the benches every day.
But it wasn't always 'cool guitar' amps, sometimes I was making Fender
Rhodes Satellite amps on bent aluminum, sometimes only Champs. I remember
two 'suits' from upstairs standing behind me occasionally doing time
studies. They actually held clipboards and stopwatches to measure how long
it took for me to attach various parts. Of course I tended to hurry more
when they were
Another really interesting fact was that he recalled that the eyelet boards were loaded/wired/soldered in Mexico! "I remember the circuit boards were pre-made, from Mexico, easy to screw into the chassis. Same with the little rectifier boards. When we had filled our cart we'd wheel it over to the Chicano chicks. They were something to behold, all chatting away while soldering so quickly, it didn't hardly seem like they were looking at the amps. After that the foreman would add the tubes, turn 'em on and set the bias."
Export models - We've confirmed that Fender amps were distributed by Hagström in Sweden. Not only that, but to meet Swedish safety codes, Hagström removed the external voltage selector switch (fitted to all blackface and silverface export models) and hardwired it internally (see photos). Notice that the original Fender back panel was removed and replaced with a Hagström panel. One has to wonder where all those factory original export back panels are! Maybe they'll show up on eBay. Another interesting tidbit is that a lot of Fenders were imported into Australia in the late 1950s and early 1960s that were stock 110-volt (domestic US) units. The Australian Fender Distributor then installed 240V - 110V stepdown transformers in the bottom of the cabinets.
I Didn't Know That! Some Fender amp expert I turned out to be. I just discovered that the silverface Bandmaster speaker cabinet (the big, tall one without tilt-back legs) is ported (see photo). I thought they were completely sealed units. I guess this is what the 1969 catalog refers to as "large, individual specially designed baffles." And all along I thought the big n' tall silverface cabs were just a macho thing to compete against the awesome looks of a Marshall half stack or full stack. But really, these cabs were large because they were of a "special design" that “greatly improves tone and volume without distortion, and permits optimum performance of the speakers. At least that's the reason according to the '69 catalog.
Also, another thing I've never seen before is a what appears to be a shipping tag of some sort (see photo). Note the check boxes for DOM (domestic US model), EXP (export model), CSA (Canada model), STD (standard) and SPEC (special). I have to wonder how often Fender used the SPEC check box and what features a "special" amp or cabinet would have?! Since the new owner would have likely removed this tag immediately upon arriving home, I’m amazed that the one in the photo has remained intact since mid-1968!
Unlike serial numbers used for most Fender guitars and basses, we know that serial number sequences are unique to a particular model or a family of models of amplifiers. This is similar to the early '50s Telecaster and Precision Bass having their own unique serial number system. Because the serial numbers are for a particular model and that chassis were stamped sequentially, is reasonable to assume that the serial number infers the Nth unit manufactured. Some caution is advised since it is likely that not all chassis were used due to defects or that duplicate serial numbers may have been stamped. Since these two scenarios are probably a very small percentage (or fraction of a percent) of total production, I’ve chosen to ignore them.
Another caveat is that it's impossible to determine the production totals for "family" models, that is, models that share a common chassis. These "families" are: the Vibrasonic (6G13) and blonde Showman (6G14); the narrow panel tweed Super, Bandmaster, and Pro; the brown Vibrolux (6G11) and blonde Tremolux (6G9); the blackface Vibrolux (AB763) and blackface Tremolux (AB763); the brown Super, Pro, Concert and blonde Bandmaster (6G7); the silverface Super Reverb and Bandmaster Reverb; the blackface Pro, Concert and Bandmaster; the Vibro Champ and Bronco; the non-master volume Twin Reverb and Dual Showman Reverb; and the master volume Twin Reverb, Quad Reverb, Super Six Reverb, Dual Showman Reverb, and Vibrosonic Reverb. There is no way to separate out production for these models, but with enough data, we might be able to do some frequency distribution and such to determine a rough estimate.
For the uniquely serialized models, the production estimates using my hypothesis, can be determined from the serial number tables. This info may make some vintage dealers cringe when they find out how common some of these amps really are, but that's just tough noogies. For example, the serial numbers for 5F6 and 5F6-A Bassman amps run from BM00001 to BM04600 therefore we can conclude that there were about 4,600 units made. How about those rarebird Vibroverbs? Well, the serial numbers for the brown Vibroverb run from 00100 to 00600 indicating a total production of around 500 units, and the serial numbers for the blackface Vibroverb run from A00100 to A05300 indicating a total production of around 5,200 units. The brown Deluxe is less common at about 4,800 units made (serial numbers run from D00100 to D04900). Anyway, you get the idea.
Just remember that if you're interested in production from a "family" model listed above, you cannot use this method. For instance, the serial numbers for tweed Bandmaster (3x10) run from S00001 to S03700. At first glance you'd think there were about 3,700 Bandmasters made, but you'd be wrong. Remember, this model shares a chassis with the narrow panel tweed Pro and Super. Therefore, the only thing we can infer is that there were 3,700 tweed Bandmasters, Pros, and Supers made in total. Sure, you could assume that if production was equal between models that there may have been 1,233 units of each model made, but currently we don't have the data to support this kind of inference.
Please note (this is very important) that there are many exceptions to the "rules" I have outlined here. Though rare, there are some amps with bizarro serial number letter-prefixes and/or missing expected prefixes that don't fit the tables. Thankfully, these aberrations are pretty rare. Just as with Fender guitars, you'll find serial numbers that should fall in a certain year, but don't. Example: Vibrolux Reverb with serial number A756254 should be a ’77, but the latest date-coded parts date it to 1978. Some serial numbers have a letter prefix plus 4-digits instead of the usual 5- or 6-digits. Likewise there are some serial numbers with an extra digit (usually a zero) after the letter prefix. Again, these are rare and exceptions to the norm.
Finally, if you don't see a particular model or year listed, it is because 1) there wasn't enough data to generate a dating table or 2) it falls under the “universal” scheme for A6-, A7-, A8-, A9-, B-, or F-series serial numbers. In the case of early tweed amps, there simply isn't enough info available at this time to accurately date these by serial number, though some rough guidance is provided. Same goes for Princetons made after 1966.
Don't get all bent out of shape if you see a model that wasn't "supposed" to be made in a certain year. Case in point; we have documented two factory-original non-reverb blackface Deluxe Amps from January 1967. The model was supposedly discontinued in 1966. Remember, FMI didn't like to waste anything (witness the Custom and Swinger guitars) so using up the remaining AB763 Deluxe chassis wouldn't be a surprise.
A6 + 5-digits - 1976
B + 5-digits - 1975, 1976
F0 + 5-digits - 1980
Examples: Vibrolux Reverb with serial number A756154 (A7 = 1977), Princeton Reverb II with serial number F077698 (F0 = 1980), and Super Reverb with serial number B10753 (B = 1975 or 1976). Note, there is enough data for B-series Twin Reverbs (and variants) to differentiate between 1975 and 1976. These are listed in the dating table. Unfortunately, there isn't enough data for other B-series models to identify the '75s from the '76s, but with your help, hopefully we'll collect enough info to do this for a future article.
Bandmaster 5C7, 5D7 (tweed)
Bandmaster 5E7 (tweed)
Bandmaster 5G7, 6G7 (brown)
Bandmaster 6G7, 6G7-A (blonde)
Bandmaster AA763, AB763 (blackface)
Bandmaster AB763, AC568 (silverface)
Bandmaster Reverb AA768, AA1069, AA270, TFL5005 (silverface)
Bassman 5B6 (tweed)
Bassman 5D6, 5D6-A (tweed)
Bassman 5E6, 5E6-A (tweed)
BM00001 to BM00550 - 1955
Bassman 5F6, 5F6-A (tweed)
Bassman 6G6, 6G6-A, 6G6-B (blonde)
Bassman AA864, AA165, AB165 (blackface)
Bassman AB165, AC568, AA270, AA371 (silverface)
Bronco AB764 (silverface)
Champion 800 (tweed)
Champion 600 5B1 (tweed)
Champ 5C1, 5D1 (tweed)
Champ 5E1, 5F1 (tweed)
Champ AA764 (blackface)
Champ AA764 (silverface)
Concert 5G12, 6G12, 6G12-A (brown)
Concert AA763, AB763 (blackface)
Model 26 Deluxe (woodie)
Deluxe 5A3, 5B3 (tweed)
Deluxe 5C3, 5D3 (tweed)
Deluxe 5E3 (tweed)
Deluxe 6G3, 6G3-A (brown)
Deluxe AA763, AB763 (blackface)
Deluxe Reverb AA763, AB763 (blackface)
Deluxe Reverb AB763, AB868 (silverface)
Dual Showman AA763, AB763 (blackface)
Dual Showman AB763, AC568 (silverface)
Dual Showman Reverb AA768, AA769, AA270, TFL5000 (silverface)
B01000 to B15000 - 1975
Harvard 5F10 (tweed)
Musicmaster Bass CFA-7010 (silverface)
Princeton 5B2, 5C2, 5D2 (tweed)
Princeton 5F2, 5F2-A (tweed)
Princeton 6G2, 6G2-A (brown)
Princeton AA964 (blackface)
Princeton AA964 (silverface)
Princeton Reverb AA1164 (blackface)
Princeton Reverb AA1164, B1270 (silverface)
Pro 5A5, 5B5, 5C5, 5D5 (tweed)
Pro 5E5, 5E5-A, 5E5-B (tweed)
Pro 5G5, 6G5, 6G5-A (brown)
Pro AA763, AB763 (blackface)
Pro Reverb AA165 (blackface)
Pro Reverb AA1265, AB668, AA1069, AA270 (silverface)
Quad Reverb CFA7104 (silverface)
B01000 to B15000 - 1975
Reverb Unit 6G15 (brown, blonde, blackface)
Showman 6G14, 6G14-A (blonde)
Showman AA763, AB763 (blackface)
Showman AB763 (silverface)
Super incl. Dual Professional (tweed)
Super 5E4, 5F4 (tweed)
Super 5G4, 6G4, 6G4-A (brown)
Super Reverb AA763, AB763 (blackface)
Super Reverb AB763, AB568, AA1069, AA270 (silverface)
Super Six Reverb CFA7106 (silverface)
B01000 to B15000 - 1975
Tremolux 5E9, 5E9-A (tweed)
Tremolux 6G9, 6G9-A, 6G9-B (blonde)
Tremolux AA763, AB763 (blackface)
Twin 5C8, 5D8, 5D8-A, 5E8, 5E8-A (tweed)
A00200 to A00725 - 1956-57
Twin 5F8, 5F8-A (tweed)
Twin 6G8, 6G8-A (blonde)
Twin Reverb AA763, AB763 (blackface)
Twin Reverb AB763, AC568, AA769, AA270 (silverface)
B01000 to B15000 - 1975
0100 to 3400 - 1970
Vibrasonic 6G13, 6G13-A (brown)
Vibro Champ AA764 (blackface)
Vibro Champ AA764 (silverface)
Vibrolux 5F11 (tweed)
Vibrolux 6G11, 6G11-A (brown)
Vibrolux AA763 (blackface)
Vibrolux Reverb AA864 (blackface)
Vibrolux Reverb AA864, AA964, AB568, AA270 (silverface)
Vibrosonic Reverb (silverface)
B01000 to B15000 - 1975
Vibroverb 6G16 (brown)
Vibroverb AA763, AB763 (blackface)
YOU CAN STILL HELP!
Thanks again to everyone who contributed information to make these dating tables possible. We hope you find them useful!!
Special thanks to Sixten Forsén at EDGAR Audio in Sweden for the information and photos, to Sam Hartley for the information and photos, to Greg at Retro Sound in Australia and Paul Mastradone for the excellent info.
Extra special thanks to my co-researchers, Devin "The Tweed King" Riebe and Greg Huntington, for their invaluable assistance with collecting data and information about Fender amps.
About the author: Greg Gagliano is going on vacation. You can try to contact him by e-mail, but don't be surprised if you get a pre-recorded message.