GSSL HELP THREAD!!!

[eqp1a]

I'm trying to fix my friends non working GSSL. Already sorted the audio path, but the sidechain is still acting weird. All controls seem to function as they should, except that the compression is far too aggressive, with clicking sounds on the attack (even at slowest settings) and far too much gain reduction, even at what is metering as reasonable amounts. Also, there is far too much make up gain. He went with the detented pot, and only the first two clicks are useable; after that the signal distorts and is too hot for any input source you'd put it in to.

Obviously I've checked and rechecked all wiring, component values and orientations, etc. but everything seems to be right. Anyone seen or heard of this before?

Edit: can post some sound samples tonight.

I've seen this exact behavior with a wrong value resistor where there should be a 120R resistor in the audio VCA sections.

Interesting...will look at that tomorrow and report back.

 

[JoelCoteBergevin]

I also tried swapping the L7915CV, with no success. Reflowed all the pads on the control board and sidechain section of the main board. All R values are correct and caps polarity is correct. Everything else is working as it should. Only the threshold being stuck in maximum compression. No matter how much I turn it, it stays the same. Until the end, where it drops really fast to like -2VDC then there's no more compression and my pushbutton lights go off.

It does the same thing with all three 50k linear pots I've tried. Really strange behavior...  I really wish someone could help me with this problem, it's driving me crazy ! Please Harpo jump in on this ?

Note: I have continuity with threshold pot wiper (center lug) and pin 8 of TL072.. can anyone confirm this ? This doesnt make sense according to the schematic, right?

 

[Zander]

Hi,


I have a problem which I have trouble finding any info on. I've built my unit back in Januari. It didn't had this problem on the bench. It works fine when I power on the unit. After 30 - 60 min it breaks down and distorts the signal badly until no signal passes through. When I cut the power and put it back on it works normally. Any idea where to look first? The power supply seems to do OK but that's only measured when the lid's taken of. Could it be the regulators failing due to heat buildup.


Thanks,


Zander

 

[gyraf]

Zander,

One of your power regulators get hot and shuts down. Measure voltages in failure mode to find out which. Then give that regulator a bit of extra heatsink...

Jakob E.

 

[Harpo]

Note: I have continuity with threshold pot wiper (center lug) and pin 8 of TL072.. can anyone confirm this ? This doesnt make sense according to the schematic, right?

Continuity testing mode might be useful for hooking up caravan backlights or sorting out a non color coded multicore.
Use the ohm setting for a more meaningful multimeter readout. Continuity will give a zero or close to zero ohm readout (pcb traces and your measuring leads have a resistance as well).
Your most likely problem sounds like a short between the two rightmost multipin connections "F"/"+" either on main board or control pcb. If so, using a magnifying glas might make it easier to spot and remove the culprit.

 

[eqp1a]

No luck with the 120R resistor in the audio vca section. Everything still looks on point, but I'm double and triple checking right now. Any other ideas?

 

[Gustav]

No luck with the 120R resistor in the audio vca section. Everything still looks on point, but I'm double and triple checking right now. Any other ideas?

check for a short where Harpo mentioned.

You mentioned you tried it without any mods added and saw the same behaviour, and you even tried changing every IC and the pot. Everything points to a short/wrong value/wrong orientation, even if you have gone through it numerous times. Is there something you could try changing in your method for checking it?

Gustav

 

[eqp1a]

No luck with the 120R resistor in the audio vca section. Everything still looks on point, but I'm double and triple checking right now. Any other ideas?

check for a short where Harpo mentioned.

You mentioned you tried it without any mods added and saw the same behaviour, and you even tried changing every IC and the pot. Everything points to a short/wrong value/wrong orientation, even if you have gone through it numerous times. Is there something you could try changing in your method for checking it?

Gustav

Thanks for the reply Gustav, was being a lazy twat with my checking. The 120Rs were actually 10Ks. Don't have any 120Rs on hand to swap in, but I'm guessing that'll do it. There weren't 120Rs mistakenly in place of 10Ks anywhere, so it looks like a mistake from pcb grinder (and then not meticulously checking resistor values from my friend as he was building) was the culprit.

Thanks all, will confirm tomorrow when I swap in the 120Rs that that's sussed it.

 

[JoelCoteBergevin]

Udpate

I found the culprit ! There's a short in the copper pcb traces at pad ''F'' and pad ''+'' on the control board. Soldered my pot center lug directly to the grey wire of the 10-pin molex (bypassed the PCB for the pot wiper connection, since it's going directly to pad F anyway) and voilà. Threshold works as expected and I got a fully fonctionnal GSSL ! Thanks everyone for helping me troubleshoot it  ;D  I guess I should've tried this earlier  :

 

[Gustav]

No luck with the 120R resistor in the audio vca section. Everything still looks on point, but I'm double and triple checking right now. Any other ideas?

check for a short where Harpo mentioned.

You mentioned you tried it without any mods added and saw the same behaviour, and you even tried changing every IC and the pot. Everything points to a short/wrong value/wrong orientation, even if you have gone through it numerous times. Is there something you could try changing in your method for checking it?

Gustav

Thanks for the reply Gustav, was being a lazy twat with my checking. The 120Rs were actually 10Ks. Don't have any 120Rs on hand to swap in, but I'm guessing that'll do it. There weren't 120Rs mistakenly in place of 10Ks anywhere, so it looks like a mistake from pcb grinder (and then not meticulously checking resistor values from my friend as he was building) was the culprit.

Thanks all, will confirm tomorrow when I swap in the 120Rs that that's sussed it.

Excellent news! (And sorry, I think I got you  mixed up with the one to Joel when I answered)

Gustav

 

[JoelCoteBergevin]

Haha no problem Gustav ! Thanks for the support and help once again 

 

[eqp1a]

I'm trying to fix my friends non working GSSL. Already sorted the audio path, but the sidechain is still acting weird. All controls seem to function as they should, except that the compression is far too aggressive, with clicking sounds on the attack (even at slowest settings) and far too much gain reduction, even at what is metering as reasonable amounts. Also, there is far too much make up gain. He went with the detented pot, and only the first two clicks are useable; after that the signal distorts and is too hot for any input source you'd put it in to.

Obviously I've checked and rechecked all wiring, component values and orientations, etc. but everything seems to be right. Anyone seen or heard of this before?

Edit: can post some sound samples tonight.

I've seen this exact behavior with a wrong value resistor where there should be a 120R resistor in the audio VCA sections.

Alright, so I switched out the mistaken 10Ks for the correct 120Rs. Fixed the make up gain issue, but now I'm not compressing at all. Thoughts?

EDIT: never mind, was being a twat as usual. the sidechain vca was flipped around (who did that??!?). Ffs. All working now!

 

[jsscalet]

So I'm still having issues with the output of my right channel. When I have sound going in, the meter reacts to the audio, it adjusts when I mess with the threshold, ratio and release.

I have tried swapping the Left and Right IC chips, removed the 5 pin molex and hardwired everything. Triple checked the wiring for XLR (even reversed wiring of the 2 and 3 pin, just in case I misread the guide.) Reflowed all the connections in the input/output.

One thing I noticed is if I remove the 10 pin molex I still get signal to go through the circuit for the left side, but nothing on the right.

But here are my voltage readings.

5532
Pin 4: -14.79 DC              Pin 4: -14.75 DC
Pin 8: 15.18  DC              Pin 8: 15.13 DC

TL074
Pin 4: 12.10 DC
Pin 11: -11.89 DC

TL072
Pin 4: -11.89 DC
Pin 8: 12.10 DC

 

[Gustav]

So I'm still having issues with the output of my right channel. When I have sound going in, the meter reacts to the audio, it adjusts when I mess with the threshold, ratio and release.

I have tried swapping the Left and Right IC chips, removed the 5 pin molex and hardwired everything. Triple checked the wiring for XLR (even reversed wiring of the 2 and 3 pin, just in case I misread the guide.) Reflowed all the connections in the input/output.

One thing I noticed is if I remove the 10 pin molex I still get signal to go through the circuit for the left side, but nothing on the right.

But here are my voltage readings.

5532
Pin 4: -14.79 DC              Pin 4: -14.75 DC
Pin 8: 15.18  DC              Pin 8: 15.13 DC

TL074
Pin 4: 12.10 DC
Pin 11: -11.89 DC

TL072
Pin 4: -11.89 DC
Pin 8: 12.10 DC

Provided we are sure you are seeing SC signal separately on the channels, and you tried swapping the IC from the working to the non working channel with the problem staying on the same side, the problem is detained to a very small area, - the output balancing circuit.

Without a scope handy, I would first arm myself with the PCB drawing and the schematic and look for a broken trace, missing solder joints (I once omitted soldering pin 8 of the VCA and spent at least an hour before I realised) and quadruple check the orientation of the 100uF caps on the output of the bad channel.

Also, you may want to check the XLR. Some types are prone to drop the connection to a pin if they arent soldered gently.

I am not completely sure, but I can't see where a short would cause dead silence, so the above is where I would start.

Gustav

 

[PeteC]

Hi there

I hope I am posting this in the right place and in the right way - apologies if not !

I have a very nice GSSL I built two years ago and its fantastic
However lately I have noticed that the gain on my right channel is getting lower than on my left channel and I cant understand why.
I have checked that its not my outboard routing to the patchbay etc as I can bypass it on my master bus in Logic X and all is still balanced OK , but if I bypass it on the GSSL itself I have the same imbalance in channel gains coming back out of the unit.  So it seems to be a problem somewhere in the unit itself.  Same issue in Harrison Mixbus - so it has to be the GSSL somehow.
I'm pretty handy with building stuff but not very expert at troubleshooting as I have very little test gear - just a basic sig gen and multimeter etc.
Any ideas where to start troubleshooting ?  - I love this thing too much to be without it for long in my little studio.

Any help much appreciated
Cheers
Pete

 

[gyraf]

Pete,

Start out by swapping L/R channels to/from the comp - this allows you to identify whether it's the comp or your system that acts up.

If you find that it is the comp, I think the only thing in there that can be damaged over time is the in/out coupling electrolytics (because they may have been exposed to phantom if accidentially patched to a micamp).

Jakob E.

 

[PeteC]

Hi Jakob,

Many thanks for your reply.

I had the GSSL out of the rack and opened up last night.
I couldn't see any issues  - even with the board out - but I had to remove the molex off-board connectors etc to get the pcb out.
When I put it all back together the problem was gone - sounding as great as it ever did now....

I guess there must have been some residual dust or oxidisation on the molex pins or connectors that was causing the problem

All sorted now .....its a great unit - thanks again for sharing this design. 

BTW Jakob, I also built 2 G-Pultecs and a G7 mic to use in my small studio alongside the GSSL and my Lexicon reverb.
All I need to do now is decide what to build next to add to my set up !  Ideas welcomed.

Thanks again - hopefully my post will help anyone else who has this issue wit their GSSL build to check over their off-board connectors.

Cheers
Pete

 

[cray]

Hello. its my second unit built.rev# 12 ,

everything is working fine. except meter doesnt move .

after checked the wiring , meter sens. resistor. and  replaced the meter , the same problem.
it works perfect except meter . any suggestion?


cant find the problem.
light on meter working. compression working and ratios  are ok.


thanks in advance!

 

[cray]

1- meter polarity  wiring  ok ,
2-  continuity    and wiring from control board to main pcb ok .
3- tried with a variable resistor on meter sens.  from 0 to 20k .. meter do nothing.
any suggestion  please?  on pcb rev #9  everything is working  at the first try , but on this rev #12  meters do nothing ,  the meter is the same on both units , so must work also on this unit.
just need to solve this to finish this project




question .
the 10p  cap . close to the meter sens resistor ,  what is its function? cuold be wrong that cap?

I have not here a 10pf  , but could to put two of 22pf in serie.

just to try if there is something wrong.

 

[weiss]

everything is working fine. except meter doesnt move .

after checked the wiring , meter sens. resistor. and  replaced the meter , the same problem.
it works perfect except meter . any suggestion?

cant find the problem.
light on meter working. compression working and ratios  are ok.

Hi cray, i assume you double checked your wiring already? does the meter light flicker or is it constant? does the meter move when turning the unit on?

best
weiss