Please help me with a dynacomp debugging

[gtudoran]

Hello, and i'm rilly sorry to start my posts witha problem. Last night i've done a dynacomp clone ( tonepad layout http://www.tonepad.com/getFile.asp?id=9) no mods no nothing just the original schematic.
I've done 2 substitutions (because i didn't have the values(
- the 4M7 rezistor i've replace it with 2 x 2M2 rezistors in series
- the trimpot that is 2K i've used a 10k

Now the problem is this: NO sound only at the max of level pot and at that position the sound is verry dimed and with a lot of distorsion. I've put a TS808 clone in front of it and the sound is louder but also with lot of distorsion. I also have a lot of humm.

Now the question is that: could that 10k trim pot to have souch an influence? Could i replace it with 2 x 1K rezistors just to make somme tests.
I don't have the posibility right now to make some mesurements bc i'm at work.

I would appreciate very much any ideea that will come around.

Thx in advance,
Gabriel

PS: I couldn't wait till i get home to make somme mesurements... i'm sure you know the feeling of a fail.

[R.G.]

Hello, and i'm rilly sorry to start my posts witha problem.

That's OK. That's how a big fraction of the people who get here get here.

Last night i've done a dynacomp clone ( tonepad layout http://www.tonepad.com/getFile.asp?id=9) no mods no nothing just the original schematic.
I've done 2 substitutions (because i didn't have the values(
- the 4M7 rezistor i've replace it with 2 x 2M2 rezistors in series
- the trimpot that is 2K i've used a 10k

The first one is OK, the last one is a problem.

Now the problem is this: NO sound only at the max of level pot and at that position the sound is verry dimed and with a lot of distorsion. I've put a TS808 clone in front of it and the sound is louder but also with lot of distorsion. I also have a lot of humm.

You have mulitple problems. If you haven't yet, read "Debugging: What to do when it doesn't work", which is always at the top of this forum.

Now the question is that: could that 10k trim pot to have souch an influence? Could i replace it with 2 x 1K rezistors just to make somme tests.

Some but not all. In fact, you can replace that trimpot with two 1K's forever. It's almost never needed.

[MohiZ]

Sounds a lot like a badly biased transistor. That's where I'd start looking, anyway. You could measure the voltages from the transistor pins and post them.

[gtudoran]

First i wanna thank you all for the help you provided.
Indeed was a bad biased tranzistor... but not because it was some component of wrong value...nooo mam... but because i was stupid and made a mistake in the pcb (when i draw it). Now everything is smooth a clear... ohh but that mistake cost me a pice of CA3080... is not much but it's smth.

Again a lot of thank to you all and especially to Owen James who helped me a lot.

PS: I didn't put a trim-pot anymore it works magniffic with 2 x 1K rezistors.

Best regards,
Gabriel Tudoran

[owenjames]

PCB mistake in the end then its always somethign simple, i had a bihatch of a time trying to simulate that circuit. juat putting a sine wave into it and then varying the amplitude with a pot was the way to go. using the 10k pot did seem to make a difference but it was hard to tell what difreence.  I also tried replacing the CA3080 with the VCA i showed you, it wokrs well.

[gtudoran]

Indeed... pcb mistake...again owen lot of thanks for you time and help.