Circuit calls for 4meg pot with switch. Substitutions?

[terryrocks]

My gemini 1 from 1965 needs a replacement switching pot. I'm not sure if it's linear or log, but the switch is at the end of the rotation.
Can i substitute a something lower than 4meg?
I really want to keep the switch capability and have thought about trading it with another similar pot from my amp.

[M Fowler]

Here is a 5 meg you might be able to use.

http://www.ebay.com/itm/HP-Agilent-2100 ... 20e8938f11

[terryrocks]

So, if I buy the 5 meg pot, I should be able to solder a 1 meg resistor to it and lower the value to 4 meg?

[Phil_S]

That trick doesn't work so well because of the taper. This is the time to look at mouser.com and brave the catalog. I think you will find 3.3M, 4.7M and 5M pots. I think the search is "switch potentiometer". Expect to pay through the nose for it. Maybe you'll get a pleasant surprise.

I don't think you'll notice the difference between 4M and 5M. 3.3M might also be hard to notice. You should meter the pot. You might be surprised at it's actual value.

The other place to call is Steve at Apex Jr. This is a phone call, not email. He's got all sorts of oddball stuff for guitar amps. Google for his business and you'll find it.

[terryrocks]

There seem to be plenty of 5M switchting pots out there.

So, using a 5M in place of a 4M should be fine?

[R.G.]

The only good ways to tell are
(1) study the schematic and evaluate what the circuit does to make a good guess
and
(2) try it and see if it works.

Older pots were often +/-20% on the end to end resistance anyway.

It depends on what the circuit does as to whether there's a problem.

If it's volume-control-ish, probably not an issue. If it's bias or speed control, then there may be issues.