These codes have been used on components including potentiometers (pots), transformers, capacitors, tubes, and speakers.The code usually consists of 6 or 7 digits such as 137634 where the first two or three digits is the EIA code for the manufacturer (137 denotes CTS), the fourth digit and sometimes fifth digit denotes the year (in this case it could be 1956, 66, or 76), and the last two digits denote the week of the year.These amps used a serial number system that was not used by any Ampegs.Unfortunately, the serial numbers are of little help for dating one of these pre-Ampeg models and EIA date codes on components were used sporadically during the early post WW-II years.Electronic Industries Association (EIA) codes can also be very useful for giving clues as to an amp's age.These codes can be found on speakers, transformers, pots, capacitors, and multi-section electrolytic "can" caps.
Each group uses a unique serialization scheme that can be used to assist in dating the amps, but in many cases, it is the features and characteristics of the amps that determine the year of manufacture.
Of course, these codes are only applicable to original components, not replacement parts.
WARNING: Ampeg amplifiers, especially the high-powered amps such as the SVT and V-series, contain lethal voltages even when unplugged and turned off.
It is important to note that parts do not always contain EIA codes, especially those parts from the late 1940s and early 1950s.
Some common manufacturer codes for parts used in Ampegs include: The Michael-Hull amplifiers can be narrowed down to a date of manufacture between 19.The only date codes that seems to be readily available is found on the speaker magnet located under the bell cover.