[sdiy] sh09 cv out drops again

[Tony Kalomiris]

Did you check the obvious, flux, contaminated keyboard contacts, psu etc..
Can't tell from bad picture of pcb overlay, but does this model have a guard ring around the keyboard sample and hold?

Describe rate of droop.
 
On 2015-01-13, at 2:01 PM, Carlos Portela wrote:

> 
> 
> After 2 months I turn the sh09 on and the cv out/pitch drops when it
> is on VCA hold.

Is a key pinned down for this. Hold only keeps VCA 'on', you will get pitch droop if not refreshed.



> 
> Replaced IC2 lf13741 by CA3140, the fat capacitor, and IC1 4558 with
> TL072. the problem persist.

Did you substitute a polypropylene capacitor for C2?
Other substitutions seem unnecessary. Because you did them all it's hard to isolate trouble.

> 
> Again removed the 2x 2sk30A GR to test them. After re-solder them the
> pitch was stable.
> I found that's (maybe) because of the heat from the iron.
> 10 min later was drooping again.

How did you test the FET's? Curious.
> 
> Also checked the sample and hold from lfo section (last time I
> switched the sample n hold FET with the keyboard tracking FET) and
> there was a kind of portmento between the played notes...

Did you try Q12 in the Sample and Hold/Noise section? Read the Service Manual about selected part , leakage test.
> 
> Any ideas what might be causing this? Bad Fets?
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