Dynacomp full debug

[drummer4gc]

Replaced all electrolytics, no change. However, pin 2 and 3 of the ota are now reading .43 - .45 V. This is the only reading that seems off from the others posted in this thread. What could be causing that?

[drummer4gc]

All right, got it working by replacing the ca3080. One thing is strange though - everything I read about compressors say that it is typical to lose some volume, which makes sense. I've played a newer dyna comp, and that was definitely the case. This old script one with the new ca3080 has tons of gain on tap though - it could be used as a pretty serious boost! It sounds fine, but I'm wondering if something has gone wrong here....any thoughts?

[cortezthekiller]

I've got an old script dyna comp and it also has a fair amount of boost from 1 oclock onwards on the volume control.
Every dyna/ross comp I've made all seem to have some amount of boost available. Unless it's used with active pickups, in which
case the signal gets slightly attenuated.

[ysba]

Hi, ressurecting this tread again 

I created another thread before taking a good look at the forum... my bad...
http://www.diystompboxes.com/smfforum/index.php?topic=114578.msg1063880#msg1063880

The main difference I got is that CA3080's pin 5 has 0.2V. I read in this thread that the normal values are between 0.4V and 0.7V. The circuit is heavily gating and distorting the sound.

May be the CA3080 damaged?

[Ben Lyman]

...heavily gating and distorting...

mine too. 3 attempts at breadboarding, much advise carefully followed from the good, generous experts here. Finally gave up and built a Mictestors RCComp.

I bought 10 CA3080's cheap on eBay delivered from China. I am about 51% Convinced all 10 were counterfeits. I need to buy from a reputable dealer someday and try again.

Where did you buy your CA3080?

[ysba]

I bought just one unit from a local retailer. I don't know abou the part origin. I live in Brazil. Buying electronic parts here is a real pain.

[ysba]

Look what I found:

http://huebnerie.de/blog/2011/01/beware-of-the-fake-ca3080e/

There it says these counterfeit parts don't have a diode voltage drop from pin 5 to 4. Maybe this is related to the 0.2V I measured at pin 5. I'm not with my circuit right now. I'll check out later.

Yuri

[Ben Lyman]

Thanks, cool read. Now I want to know what I can do with 10 LM4250's! lol 

[PRR]

> what I can do with LM4250

Earrings?

Or fake LM308 in that fuzz which sounds best with a poor opamp. Study and fiddle the bias currents.

It is not a natural gain-control like the '3080.

[Ben Lyman]

Earrings would have to be "clip-on" for me... hardeeharhar.
Maybe I could throw them in some fake cobweb decorations this Halloween... bah-dump tshh!!

[ysba]

So finally I got a solution. My problem was a counterfeit CA3080. Pin 5's voltage was low because the internal circuit is an unknown IC.

I bought another CA3080 from another retailer and this one works properlly.