Dating fender cts pots
- All vintage USA Big Muffs have source-date codes stamped on the underside of the potentiometer cans, or “pots”.
The pots are what the knobs are mounted to, essentally manually adjustable resisitors that control the voltage across a circuit.
These date codes will contain two letters of the alphabet which refer to the year and month of production, and may be interpreted as follows: In the absence of the rubber-stamped date codes, EIA numbers taken from the transformers may allow you to determine the date of production of your amp.
These numbers always begin with "606" , and are followed by three or four digits in various combinations.
The Muff could have been made months or even years after the pots were purchased as it is known that Electro-Harmonix bought the pots in bulk, as did Fender, and other companies at the time.
The next two numbers after the manufacturer number are the year, and the last two numbers are the week of the year the pots were made.The first three digits represent the manufacturer, the next one or two represent the year, and the last two will be the week it was made.Six digits were changed to seven starting in the 1960’s making the year two digits instead of only one.The EIA assigns each manufacturer a three-digit code (there are some with one, two or four digits).When dating an instrument by the ‘pot code,’ keep two things in mind: The potentiometers must be original to the piece (new solder, or a date code that is off by ten or more years is a good giveaway to spot replacement pots); and the pot code only indicates when the potentiometer was manufactured!