Engineer's thumb Vero troubleshoot

[jtn191]

I should be able to get this but my brain's hurting...

when all controls on max:
Ic 1 voltages= 8.97, 353mv?, 0.92, 0, 4.24, 1.0mv, 1.1mv, 8.97

Ic 2: 1.4, 1.1, 0.9, 0, 0, 7.45, 8.05, 8.97

Ic3: 1.0mv, 0.63, 7.94, 0.9mv, 32mv, 0, 0, unstable, unstable, unstable, 8.98, 32mv, unstable, unstable, 0.5, unstable

Using this layout



Thanks

[jtn191]

Ok, I got it working...I had R7 in the wrong place and a couple shorts.

[jtn191]

Looking at this again and trying to figure out why it's not compressing much...

My IC2 pins 5,6,7 have low voltages below 2v
And Q1 too...can't figure out where the problem might be

[midwayfair]

Looking at this again and trying to figure out why it's not compressing much...

My IC2 pins 5,6,7 have low voltages below 2v
And Q1 too...can't figure out where the problem might be

Hm. What's the voltage on IC2A? check the junction of the two Vb resistors (the pair of 1M that bias IC2). If you're getting proper voltage there, then there aren't too many components that can affect the voltage on the second half of the op amp. Also, pull Q1 if it's in a socket and see if that fixes things.

[jtn191]

Ok, here's the voltages now:
IC1: 4.45, 4.40, 3.92, 0, 4.19, 4.45, 4.45, 8.86
IC2: 4.79, 4.45, 3.95, 0, 0.85, 1.98, 1.38, 8.86
began reading IC3 but ran out of time on my lunch break: 1.32, 0, 4.45...

the voltage at the junction of R13 & R14 was 4.19v

[midwayfair]

Not entirely certain, but the voltages may not be wrong. That doesn't mean it's working right, though ...

What PNP did you use for Q3?

[jtn191]

It's a BC327, voltages on that have been low too.
Everywhere else people were getting ~4v on pins 5,6,7...that's the only reason I can think of that I'm not getting much compression and below unity gain