N Cook wrote:
Does anyone know of any standard or authorative source for such
designations.
eg
50KA - lin ?
50KB- log ?
50KAB - lin/log , semilog?
50KBA - log/lin ?
and does a B prefix mean a centre pick off fourth terminal, or 1/3&2/3, or
any fixed track tap terminal or what if anything a B prefix means. ?
And while at it any other letter designations eg for cosine track, or even
wire/wound etc


I think it`s A = lin, B = log except when it isn`t

the marking conventions changed some time ago
Pot Markings
Now, this should be dead easy - a simple code to indicate the resistance and law of a pot should cause no grief to anyone, right? Wrong! It wouldn't have been so bad if someone hadn't decided to change it, and even then, it wouldn't have been so bad if there was no overlap between the "old" and "new" "standards" ... I think you can see where this is headed by now.

Taper Old Code New Code Alternate
Linear A B LIN
Log (Audio) C A LOG
Antilog F N/A N/A

Wasn't that a nice thing to do? It is obviously important to check before you make assumptions, or you can easily get the wrong type - especially if working on older equipment.

At least the resistance marking is usually sensible, so a 100k pot will be marked as 100K - but not always. The coding system used for capacitors is sometimes used as well (especially on small trimpots), so a 100k pot could also be marked as 104 - 10, followed by 4 zeros, or 100000 (100k) ohms.




http://sound.westhost.com/pots.htm#markings

Ron(UK)