[R-390] Local & Line gain potentiometers R390/A

[Charles Steinmetz]

Craig wrote:

>The question is what: What is the translation for RV4ATSA252D? Panel mount
>is a yes, 2W is a yes, ¼ X 7/8 inch shaft is a yes. Taper????? I’ll also
>dare to ask what is today’s replacement?

"252D" means 2.5k ohms, log taper.  Is the shaft 
really 7/8", or is it 5/8"?  (If it really is 
7/8", check to see where the setscrew divot is on 
the shaft -- if it is farther from the end than 
1/4", a 5/8 will work in its place.)

I believe RV4 and the commercial equivalent, the 
"Series K," are still available.  You might try 
State Electronics or ETI Systems.  Digi-Key has 
RV4 pots, but not 2.5k log taper.

The pots in a 390A are hot-molded carbon, but you 
may also be able to get conductive plastic.

If you don't care about originality, any 2.5k log 
pot should work fine.  Actually, any log pot from 
2k to 10k should work fine.  And there is no need 
for a 2W rating -- 1/4W is plenty.

This 5k audio taper Alpha part ($1.50) looks like 
it might have a form factor that will work:
<http://www.mouser.com/ProductDetail/Alpha-Taiwan/RV16AF-20-15S1-C5K/?qs=sGAEpiMZZMtC25l1F4XBUxcT8FFa2pT4Cm7Y%252b7ehOxI%3d>

I'm sure other suppliers have similar parts with appropriate form factors.

Best regards,

Charles