Dating a fender amps by transformer
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. 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. The early amps (woodie and tweed) had serial numbers handwritten on the tube chart.
These appear to be used sequentially independent of model.
Here is an example: EIA 606-4-21 would mean the 21st week of 1964.
It is also advisable to add about 6 months to the date to allow for time these parts may have spent in storage.
If three digits are present, the first digit would refer the units of the year i.e. If four digits are present, the first two digits refer to the year i.e. The last two digits would refer to the week of the year i.e.
("26" would mean the 26th week or approximately June).
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.
Always remember that pots, speakers and transformers may have been changed!!
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. 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) Speaker codes (if speaker is original) 5) Transformer codes (if the amp doesn't have date codes on the tube chart) 6) Cosmetic features (flat/raised logo, tweed/tolex, blackface/silverface, rough/ smooth blond tolex, white/skirted knobs, TV-front/wide-panel, etc.) 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.
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. 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.
Dating Fender Tube Amps by Serial Number, Part I by Greg Gagliano Copyright 1997, 20th Century Guitar Magazine. Well, we'll get to good parts, but first a little background information is in order.