[sdiy] Rick Jansen Moog filter revision -> problem!

[Needham, Alan]

Maybe a first step could be to measure the DC voltage at Q14 base to 0v with no audio signal, and DC voltage Q14 emitter to 0v.
If Q14 seems to be stopping the signal then maybe it isn't biassed on enough (readings above help to (dis)prove that).
A transistor should have about 0.6v or 0.7v (depends who you ask!) from base to emitter when working normally.
If the above seems OK, then measure the voltage across R19, this, with some Ohm's Law, will tell us the ladder current.

These three voltages will at least help to isolate the Exp Generator as a possible fault and indicate biassing on the ladder.

My guess,
	Alan


-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl]On Behalf Of Rutger Vlek
Sent: 20 August 2007 12:52 PM
To: synth-diy at dropmix.xs4all.nl
Subject: [sdiy] Rick Jansen Moog filter revision -> problem!


The problem is that no sound comes out of the filter (even when sound IS going in, hehe ;) ). With a scope I confirmed that the signal reaches Q14. However, I can't see the signal being forwarded through the 'ladder' and it certainly does not reach the output buffer (IC5). I'm running the circuit on +12 and -12 V instead of 15. What could cause my problem?

Kind regards,

Rutger

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