DATING FENDER AMPS BY SERIAL NUMBER, PART V
by Greg Gagliano

Directions: On the right side of the screen you will see a series of boxes listing colors. From those colors, choose the one that best resembles the color of the toy that you are trying to identify.
Back to Other Triode Pages These are codes often seen stamped on components found in US made vintage tube equipment. This list is circa 1955, and some.

The serial number format for the furnace data plate shown above uses the last three digits of the serial number for the year and week of manufacture, with the third from last being the year and final two numbers are the week. So “740” means this unit was produced in the 40th week of 1967, 1977, or 1987.

They said it couldn’t be done…
Over 6 years in the making…
Finally, what everyone has been waiting for…
How to date Fender amps by serial number!!

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?

FUN FACTS
Oddlings – Yet another printing error has surfaced, this time from the FEI (pre-CBS) days. A 1957 tweed Vibrolux was reported with a tube chart printed with circuit “5E3” (tweed Deluxe) instead of the correct 5F11 (see photo). Clearly Fender wasn’t afraid to use incorrect parts when they were in a bind. We also received a report of a tweed 5G12 Concert. The 5G12 Concert is the earliest version from very late 1959 and early 1960 so the existence of a tweed example, while extremely rare, is certainly plausible since Fender was making lots of tweed amps during the same time period. It’s unknown if the tweed covering was a mistake (“Oops, I thought this was a 4x10 Bassman cabinet that I was covering”) or intentional, perhaps as a special order.

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 ’66 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
there, and I would fumble more, too.”

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.

Mid-1968 Super Reverb export model modified by Hagström for the Swedish market. Note the removal of the voltage selector switch and hard-wiring. Also note the vertical black lines on the control panel (found on earliest silverface amps) and the large ceramic power resistors coming off the power tube sockets which indicates the AB568 circuit.

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!

PRODUCTION
Along with dating amps by serial numbers, we were interested in determining production totals, if possible. There is some debate about how to interpret the production code information on late ‘50s to mid-1967 tube charts and Greg Huntington is still working with those. One thing we know for sure is that production codes can help date an amp to a particular month within a given model run. Greg and I also disagree about determining production from serial numbers. I will present my hypothesis here and let Greg present his side of the story in a future article.

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

Transformer Serial Number Database