[sdiy] OBX trimming (was Polyphonic tonal disorder!)

[Steve Lenham]

From: "John Mahoney" <jmahoney at gate.net>

> While we're on the subject, do you have a favorite replacement trimmer for 
> the OB-X?

Hi John,

Sorry - I'm a bit bit behind in replying to this one.

The OBX I worked on had a mixture of cermet trimmers for critical 
adjustments and carbon ones elsewhere. Although the generally held opinion 
seems to be that they are a major weak point, all bar one of the trimmers in 
this machine were in generally good shape and I was able to calibrate it 
tightly enough to please my client.

I would go for cermet trimmers in all positions, but wouldn't be fussy about 
exactly who made them. The one I used recently was from a range of unbranded 
cermets supplied by Rapid Electronics in the UK.

If you are replacing original trimmers, beware the slightly unusual 
footprint. They need 10x5mm pin spacing, which is common in carbon trimmers, 
but most cermets are 5x5 or even 2.5x5. Obviously, if you are adding 
something (like a resonance trim) then you can use whatever you like - 
sealed multiturns are great if money is no object.

HTH,

Steve L.