GSSL not working, where to start?

[Coldsnow]

Well I got signal. The channels seem to work now but none of the controls work or the side chain. I've swapped out the ic's and still nothing. Thank you guys for all your help. Any suggestions where to go now?
Thanks

 

[jensenmann]

Check all the controls systematically:
bypass works?
Does it compress?
gainmakeup working?
which release setting works (not)?
which attack setting works (not)?
which ratio setting works (not)?
threshold working?
Meter working?

Let us then know. Thats the way to surround the fault.
If you found a setting/control not to work then check wiring again. Check if the pots/switches are wired ok. Did you mount the tantalums right ? They have a polarity, IIRC the polarity is also on the silkscreen. If they were mounted wrong desolder them, throw them away and mount new ones.
:sam:
Jens

 

[Coldsnow]

It doesn't appear as though any of the controls work. The make up gain does nothing, the threshold appears to have no effect nor does the attack and release. The bypass switch doesn't appear to either. How can I bypass the Bypass switch to "compress on" so I can work with the other sections first.
Thanks

 

[Coldsnow]

I am assuming to bypass the bypass, you connect "com" to "on", and connect A to A2 together.
My reasoning for doing this is to rule that out as a problem. I can always connect it back later.

 

[jensenmann]

If it passes audio and nothing else works you can at least hear if it compresses when you increas input level.
Anyway check supplyvoltages at pin 7 against pin2+6 at sidechainVCA (+12V), then the -12V supplyvoltage at 3k9 resistor connected to pin5 at the sidechainvca. Same with TL074: pin4 against 5 should be 12V, pin 11 against pin5 should be -12V. Same with TL072: pin 8 against 5 should be +12V, pin4 against 5 should be -12V.
Then measure Voltage at makeuppot. Here you should have 12V between the nonwipercontacts and 6V in middleposition between CW (Clockwise position) and wiper.
Next is the thresholdpot. Here you should measure 24V between nonwipercontacs and around 12V between wiper and CW when it´s in middleposition.

Jens

 

[Coldsnow]

Thanks for the input Jensenman, It does not appear to sound compressed when audio is running through it.

OK
all the values on the VCA, 3K9, TL074, TL072 all shake out fine.


I swapped out the tapers and that didn't help.
Is my bypass of the Bypass correct ("com" connected to "on", A and A2 together)?

 

[Coldsnow]

OK
I now have the threshold reading at -12, +12, +12 on the poles. The makeup at +12 and +12 on two of the poles. They still do nothing, however.

 

[jensenmann]

Did you mount the sidechainVCA correct? It´s supposed be reversed with respect to the channel VCAs. Check mountingdirection for the TL072/074, too.
Check if all diodes are in the right direction, same with 22uF cap at pin7 of TL074.
Did you measure every resistor for correct value before soldering it?
Do you have a scope/tonegenerator?
Jens

 

[Coldsnow]

Yea the VCA is mounted correctly as are the other components. I've checked and checked them.
I don't have a scope or tone generator.
Thanks again,

 

[jensenmann]

OK, then I´d suggest you to go to the realtraps homepage:
www.realtraps.com
download the testtone CD and burn it. The CD contains sinewavetracks in 1Hz steps. If you use track5 (50-59Hz) and feed it in the compressor input you´ll have a defined signal which is in the frequencyrange your DMM can recognize.

then measure at pin 1 of the sidechain VCA if you get AC there. If so check it at pin8. If so check pin6 at TL074. If it´s ok go to pin 7.
If you have AC here we have to leave the AC-world and have to go to DC in the following circuit. Unfortunately I can´t tell you the exact voltages at those points since my Gssls are not here right now. Maybe you find exact values for comparison in the Gssl help thread.
Jens

 

[gyraf]

the input pin of the VCA's shows no voltage, as they're current-input (virtual ground) devices. But you should have a signal at the output pin..

 

[jensenmann]

thanks, Jakob, I forgot about that...
Jens

 

[Coldsnow]

Thanks I'll give that a shot.

Another question though.
My VU meter is reading heavy compression going on, however, none of the controls appear to effect the neadle reading. Does this suggest that the side chain vca is working but something in the controls is messed up?

My thought is to disconnect the attack, release, and ratio switches and hard wire them and see if I get a different result.
What do you think?

 

[jensenmann]

well, if your meter works that´s a good sign( I mean when it shows the real deal). Then the area of the fault is possibly around the TL072 stage.

Let your needle dance around 10dB GR and measure DC at pin 8 of TLo74. There should be 1V or more. Then measure DC at Pin 1 of the TL 072 (makeupgain to 0). I guess there will be nothing, otherwise it should work. It´s only to make sure that we are in the right place.

If there´s nothing: check all resistor values around the TL072 stage. Check again if it´s monted in the right direction. Check if there are shorts on the PCB in this area. If that´s ok the get a new TL 072 and try again.

If you measure DC: check the area of pin3 at the channel VCAs for shortcuts and check the values for all resistors around there.
Jens

 

[Coldsnow]

Am I correct with how I bypassed my "bypass switch)?
Com connected to On. A connected to A2?

 

[jensenmann]

Yep, that´s ok
How is it going?
Jens

 

[Coldsnow]

Hey Jens,
IT WORKS. and sound great at that. It was a wrong resister the 100K. I don't know how I kept missing it. I really appreciate your help. Thank you very much. The last step is to soilder in the VCA's. I used the THAT 2180's and they don't fit tight in the standard holders people are using, so you have to wiggle them once in a while to work. After soldered in all should be great. The only bad thing is the compressor sounds so good I might have to build another one or maybe I'll try the G1176. Here we go again.

 

[jensenmann]

I did two of them for that reason. I knew the original SSL before. What then happened was that a friend appeared, heard it and took it to his studio for testing and never gave it back. Now I have to do another one ( this time with all the mods) - or maybe two :grin:
best
Jens

PS where do you live in Ohio? I have a lot of relatives overthere.

 

[gyraf]

Good work, Jens..

Thanks!



Jakob E. :thumb:

 

[Coldsnow]

I live near Canton about an hour south of Cleveland.