GSSL HELP THREAD!!!

[bubba_b]

It seems like every time I fix one thing that's wrong, another one pops up. Here's my newest problem:

I have audio and compression just fine in the right side (yeah!). The left side, however, is considerably lower (-15db) and distorted, but intermittenly seems to work and then instantly clip back down to -15 again (all within about a half of a sec.). It sounds like a short somewhere, but I'm not exactly sure where to look. I checked for shorting on the 5532's between pins 1-2. Right side reads 2.2mV, left side reads 0.2mV. Swapping the chips makes no difference. I've ruled out the 10k resistor and 100p cap coming off pin 1 (the 100p goes back to pin 2). Any ideas where to look next I'd greatly appreciate.

I know I'm close and it's keeping my spirits up. I just pray that once this is fixed, it'll be all done and ready for rock! :grin:

p.s. I have a small audio file I can email to anyone if hearing what it's doing would help.

 

[bubba_b]

bump, please

 

[gyraf]

..Check, check and double-check everything. And try swapping ic's between channels, if one channel is fine...

 

[bubba_b]

Thanks, gyraf. I checked, checked and re-checked every solder joint on the board and they are all fine. I even resoldered a few that were even slightly close to each other just to make sure. Also, swapping IC's had no effect. The same (left) channel still has the same problem.

It seems to be doing this: 1) on initial start-up after sitting off for awhile, it works in both channels for about 5 seconds, then the left goes down -15db and is fuzzy. It stays that way thereafter. 2) I didn't really notice it at first, but my friend pointed out it sounds "phasey", and it does. Kinda like it was recorded in a small wooden box? 3) controls all work, but meter doesn't move.

 

[radiance]

Did you also swap the VCA's?
Obviously you did cause they're IC's as well but just in case....

 

[Underthebigtree]

Hi folks -

I have an input problem. Perhaps someone else has some insight, 'cause I'm out of ideas. Here goes:

Left input is several DB quieter than right. Everything is fine coming into the 5534 input opamp. Pin 6 coming out is significantly quieter than the same on the right opamp. I've swapped the IC's, no change. I've swapped the dbx chips downstream, no change. I've checked the values of the 22K resistors around the input circuit, and they all seem OK.

A gain problem like this has to be the feedback resistor, right? I'll re-solder for cold solder joints, but if anyone has any other ideas, I'd love to hear 'em.

Thanks,

Nick

 

[bubba_b]

radiance,

Yes, replaced both VCA's and no change.

 

[bubba_b]

Found a bad 100u cap in the left output channel, but replacing it didn't fix the thing. If anyone could please take a listen to what it's doing and maybe give some insight as to what in the world this thing is doing, I would be eternally grateful. Here is the file. It starts out compressing, then you can hear what it does when I turn up the makeup gain, then switch to bypass, and then back into compressing mode.

I can't stress enough how many times I've gone over this board looking for solder bridges and came up empty. Something is just plain bad, I just don't know what.

 

[radiance]

That's a bad link...

 

[Flundran]

I have a stange voltage drop right after the W04 bridge. The '-' side is right (-17.8V.. I have a 2x18 trafo) but on the plus-side of the bridge I only get +5.20V. I measured the W04 and it seemed to be ok. What can be the problem?
/Flundran

 

[gyraf]

Flun,

Something is shorting the output of the 7815 regulator.

Check, check, and double check..

Jakob E.

 

[Flundran]

I unsoldered the wire to the input of the 202xt, and suddenly the voltage is right. Does this mean something is wrong with the VCA? How do I check it?
/Flundran

 

[bubba_b]

radiance,

Sorry about that. Here is the file, again. If this doesn't work, let me know. Thanks for trying.

 

[bubba_b]

bump

 

[Flundran]

I have a stange voltage drop on the + side right after the W04 bridge. I only get +5.20V. I unsoldered the +15 pin on the left VCA, a 202xt, and suddenly the voltage was right. I've switched places of the two 202xt:s, and the result are the same.
Jakob said that something is shorting out the +15 rail. Does this mean the sorting out is somewhere after the 202xt:s in the chain, or are the vca's broken?
Anyone got any ideas?


/Flundran

 

[gyraf]

If one VCA kills the +15V supply when it's soldered in, there's a pretty good chance that that VCA's broken...

Jakob E.

 

[Flundran]

In that case both are broken. I switched place and the same problem accours..

 

[gyraf]

Does It happen with the same VCA soldered in, or with a VCA soldered in the same place?

If it's a place problem, then check the pcb and soldering. If fault follows one of the VCA's, then this is broken..

Jakob E.

 

[FrankSL]

Don't know if this has already been noticed, but looking at the pcb I found that the 100R resistors on output are in fact put after the parallel of the 100n and 100u caps, or connected directly at the output terminals.

I don't think this cause problems, but maybe is possible to correct the schem accordingly, just to have it exactly match the pcb...
If I'm wrong please beat me... :grin:

Frank

 

[gyraf]

Frank,

You're right - but the order of those dosen't matter...

Jakob E.