Potentiometer code dating
Russian made Big Muffs have Russian made pots, usually 100k linear taper. If you replace an old pot with a new one of the same size, it is sometimes hard to find pots with the same pot shafts that fit the old knobs.You can use 100k audio log taper for the volume pot. You can sometimes pull the shafts out of the old pots and install them in the new ones.250K is the impedance of the potentiometer, but it is the number to the right you should take a closer look at.
Loosen the two screws holding the controlplate, turn it upside down and you will find some numbers.For vintage USA Big muffs, carefully bend back the four tabs on the top/back of the casing on the old pot, slide the casing off, then remove then shaft. Linking to this website is allowed, but copying the text content is strictly prohibited without prior authorization.Open the new pot this same way and install the old shaft. Something to keep in mind, some pots are letter coded with A and B to represent linear or logarithmic, but there is no worldwide standard for which is which. No part of this work may be reproduced, stored in a retrieval system, or transmitted in any other form, or by any means, electronic, mechanical, photocopying, recording, computer networking, or otherwise without prior permission in writing from the copyright holder(s).In the second string of numbers, the first three numbers are a code identifying the manufacturer.
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 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.