How to date a vintage Fender guitar amp
Posted on April 21 2020
Vintage Fender guitar amplifiers are easy to date if you know where to look. A guitar amplifier is more than just a guitar speaker; it's an essential part of a guitarist's tone. Fender guitar amplifiers made between 1946 and 1980 have many parts that are easy date. If you're looking for "how old is my Fender amp?" then you've come to the right place.
Here are the three most important places to look to help date your Fender guitar amp: tube chart code and transformer date codes. Since the serial numbers on Fender guitar amplifiers were pre-stamped on the chassis before the amp was assembled, they're not a very good way to date the amp. Vintage Fender guitar amp serial numbers are not entirely sequential so a lower number doesn't necessarily mean an older amp. We don't have documentation to cross reference these numbers so any attempt to date with a serial number is often a few years off.
Tube Chart letter date stamps
Fender amplifiers from around 1953 until 1969 almost always have a two letter ink stamp that indicates the year and month the amp was assembled. You can find the tube chart by looking in the back of the amp on the left or right wall. Here's an example of a tube chart on a vintage Fender guitar amplifier:
This tube chart has the large ink stamp with letters "OL". These two letters indicate the year and the month that the amplifier was assembled. In this case, "O" indicates 1965 and "L" indicates December. Do you see a two letter ink stamp on the tube chart of your vintage Fender guitar amplifier? Here's a chart below that shows what year and month your amp was assembled:
Letter -- First Digit -- Second Digit
A (not used for year), January
B (not used for year), February
C 1953, March
D 1954, April
E 1955, May
F 1956, June
G 1957, July
H 1958, August
I 1959, September
J 1960, October
K 1961, November
L 1962, December
Transformer Date Codes
The next place to look for help with "how old is my Fender amp?" is the power and output transformer date code. The transformers the large square or rectangular boxes hanging down from the chassis on the inside back of the amp. Fender utilized a few different brands of transformers but the most common are Schumacher and Triad. Here is an example of a chassis that has been removed from a Fender guitar amp so we can see the transformers:
This vintage Fender Vibro Champ amp chassis shows the power transformer on the left (large black rectangular) and the output transformer in the middle (smaller aluminum colored rectangular shape). Both of these transformers are original to the amp and have date codes that indicate the year and the week that the transformer was manufactured.
The output transformer here (middle) has two codes but only the bottom code is helpful for dating. The date code on this transformer reads "-606-6-27." "606 is the manufacturer's code (Schumacher), "6" indicates the last digit of the year so this one could be 1956 or 1966, and "27" is the week of the year. Since we think the rest of the amp was made in the mid 1960s, we can assume that this date code indicates the 27th week of 1966 made by Schumacher.