GSSL HELP THREAD!!!

[flintan]

Do you have a load on it? These type of regulators need to pass current in order to regulate correctly.

 

[spica]

I have tried the diode/capacitor latch up fix at the 7815 and that has helped a little... The voltage still drops but only to 13.5-13.9V.. this is both with load and without.  

However, when I put all the IC's back in the voltage slowly drops back down to 6V.  I may have isolated the problem a bit as this only happens when I put in the Sidechain VCA.  I have swapped this IC so I'm pretty sure the chip is ok - unless both I tested are bad in the same way.  I'll look around this area of the circuit and see if anything seems wrong.

The frustrating part is that I just built my first GSSL (this problem child being the second) a couple weeks prior and it worked without a glitch using all the same components (minus 2181LC's in the sidechain in this one vs. 2181LB's in the first)  

ADD On:

I should probably add that I do not think the +15V regulator is the problem anymore..  The voltage coming into the regulator is also getting pulled down.  The voltages coming into the main board after the CRC board are -26V and +15V (after starting around +20V).  This is with all everything hooked up and all IC's onboard except for the main board sidechain VCA.  After looking at the schematic, I find it very odd that the sidechain VCA has any influence on the +15V rail as the only power coming to it is from the +12V regulator which seems ok. 

 

[spica]

After putting the main board sidechain IC back in, the voltage coming into the main board (before the regulators) is +6V (after being pulled down for 10-15 seconds) and -34V.  At initial fire up, they are +/- 20-21V.  There seems to be some sort of +/- voltage teetor totter thing going on.  Could the rectifier diode on the CRC board have some sort of problem?

Maybe some problem with grounding?  The difference between the +/- seems to be be a consistent 40V-ish.  For grounding, I have one ground point from the 0V on the output of the CRC board connected to a star ground that is connected to the IEC power ground.  The 0V from the CRC output is also connected to the 0V on the main board.  I'm pretty sure this should be fine as all ground on the main board would be connected to this ground.  XLR connectors are connected to the case (not the board).  

UPDATE:  I swapped out the rectifier diode on the CRC board and that didn't make a difference.  The power coming into the CRC board from the transformer is a constant +18VAC on both sides.  The + DC voltage still starts to drop down though after the rectifier diode.

 

[spica]

PROBLEM SOLVED - Last thing you check, as always.  After some more testing I noticed that everything was groovy if I connected the CRC output to the main board with jumpers instead of the cable I made with molex connector ends... the problem was that cable.  The common 0V pin wasn't connecting properly between the CRC board and main board. 

:-[ I probably should have figured that out a little earlier in the process.  I think the real symptoms point right to it - ground was floating so the +/- rails tilted but stayed the same relative to each other.  Feel free to explain this better if I'm not right - I'm not much of an EE... clearly

Thanks for letting me talk through it!

-Tony

 

[spica]

Ayman, do you have a way to scope the side that isn't passing audio?  You could use your DAW and send a signal into that channel and use probes back into an input channel on the DAW and see where in the circuit path the signal drops out.  Maybe there's a bad connection somewhere or component mistake.  I'd start tracing the signal though. 



Nashkato, I had a couple similar issues with bad cable connections - seems like you're having the same issue. 

 

[nashkato]

  Nashkato, I had a couple similar issues with bad cable connections - seems like you're having the same issue. 

thanks , i´ll guess  i´ll be hardwiring the turboboard as first step

 

[spica]

If you were using pins, you could try alligator clips to start with to make sure that was your problem.

 

[electrisizer]

hi ive a problem with my GSSL:

i explored that the neg. voltage of the TL074 is about -19V.

I followed the wrong voltage and discovered, that the 78L12 and 79L12 has an input of 22V.

the 78L12 get it to 12V

the 79L12 get it only to 19V

BUT the problem seems to be the 22V input at this stage or am i wrong?

next thing that produces this 22V is the bridge rectivier. my local electronic dealer gave me a "B 80R"
http://www.datasheetcatalog.org/datasheets/185/233067_DS.pdf

my transformer is a 2x15V that fits on the PCB - so i think the problem is the bridge rectivier...

can someone give me an advice?

thanks

 

[Voodoosound]

Hi,

I am building my second GSSL but this time with THAT2150A VCA'S.
It compresses okay but..
My problem is that it distorts really quick like im overloading the input or something or maybe the output ...?
Also output level is much lower than my other GSSL with THAT2180 VCA'S

If i put my 2180 VCA's in this unit , the input/output problem seems solved.
I have kept all original values from the diagram for the original THAT2150A VCA's ..

Maybe someone here can help me ?

Thanks !

Paul

 

[ncoak]

just finished my first build, a permanently turbo'd 2x ssc & crc board gssl...worked like a charm the first time i fired it up. big thanks to everyone here for the wealth of information, i literally couldn't have done it without you!

 

[Ayman59]

Thanks Spica.

Finaly I solved the problem. Right VCA socket wasn't contacting correctly VCA tips so I changed it.

Does anybody can tell me why I do have an incredible amount of gain on the Makeup pot? The sound is heavily distorded if I turn the pot more than a few degrees to the right?  :-\

 

[electrisizer]

@ayman what VCAs are you using?
have u checked this?

http://diy.fischerworks.com/gssl_vca.shtml

my makeup distorts too when i put it over half of scale.
but only the left channel 

my voltage on TL74 are +12 on and -13. can this cause the distorion or is it in the normal range?

 

[theone23]

hey everybody.....thanks for sharing skills in this forum

im building a gssl with dbx202c and a 2180A in the sidechain ( could not find any 2150)

may somebody tell me if that's a problem......i know the 2150 is closer to the specs. of a 202c but

they're hard to get.

i changed the 3k9 to 5k1 left out the 47r on pin 4 of vca........and

left out the 10K res on the sidechain vca too.......i did a test finally and it works and sounds good.....

BUT im not sure about the 10K res, could not find any info..... ???

So, should i leave it out.....? and what's the 10K res on da sidechain for ???

would be glad to get some informations on that

 

[colombian]

Does anyone care to share the wiring for :

1.  Wiring of illuminated EAO DPDT switch for POWER. I am guessing for the light you use the Control Board Power led?

2. Wiring an DPDT EAO switch for the Bypass function.  Basically I guess i need : Compression IN/OUT, Disable Makeup gain, Illuminating Light.  So... I am missing one pole?  How have you people accomplish this?


A contributor that goes with the nickname of SSLTech mentions a relay directly installed to the Control board, but his explanation is not very clear and I am yet to see any schematics.

Thank you.

 

[mac]

hey Columbian,

my bad drawing using SSC edited by the very knowledgeable Harpo is found here http://www.groupdiy.com/index.php?topic=16113.220 for relay connections...

most info is here if you search for it long enough!

good luck,
mac

 

[colombian]

Hello MAc,

thank you for replying and providing the information. I have seen that schematics however I do not use the Super side chain, nor I have a need for it.  Consider my build the basic Gyraf design , no mods.

I did indeed look for info about this here, but nothing clear. Its simple, I want to use EAO switches for power and bypass......I imagine I am not the only one who had try.....someone must have a wiring diagram!!

Thanks!!

 

[spica]

22v DC coming after the rectifier diode is fine and normal with your 15VAC transformer.  It looks like your 78L12 is behaving correctly as it is outputting 12V.  Looks like your 79L12 is suspect though. 

Have you tried swapping it out?   

hi ive a problem with my GSSL:

i explored that the neg. voltage of the TL074 is about -19V.

I followed the wrong voltage and discovered, that the 78L12 and 79L12 has an input of 22V.

the 78L12 get it to 12V

the 79L12 get it only to 19V

BUT the problem seems to be the 22V input at this stage or am i wrong?

next thing that produces this 22V is the bridge rectivier. my local electronic dealer gave me a "B 80R"
http://www.datasheetcatalog.org/datasheets/185/233067_DS.pdf

my transformer is a 2x15V that fits on the PCB - so i think the problem is the bridge rectivier...

can someone give me an advice?

thanks

 

[ilfungo]

hello guys
I found the 12V relay  (for super side chain board)
and the specification says that work from 8v to 18v
might be okay?
to bypass the SSC board  (2 + turbo) I have to use 2 Relay (1 per board)?
thanks

 

[electrisizer]

22v DC coming after the rectifier diode is fine and normal with your 15VAC transformer.  It looks like your 78L12 is behaving correctly as it is outputting 12V.  Looks like your 79L12 is suspect though.  

Have you tried swapping it out?

   

high.
ive measurd from time to time. now its on 15,6V after the 79L12...
yesterday GSSL worked, today after measuring testing around both chanels distort!!!  :-\

i think i remove this 78/79L toy and put a TO220 7912 in. ive read that my electronic supplier reichelt.de is known for bad quality regulators...

 

[spica]

I've still got a few gremlins in mine that I haven't yet been able to shake down. 

Passing audio, make-up gain works, but no compression.  The threshold pot adds a bit of harmonic distortion as it moves from +20 to -20 but no GR. 

Scoping through the audio path, I've noticed something puzzling - I'll have a robust test signal on one side of a resistor and nothing on the other side in several spots where I expect signal to be.  For example, I believe the 27k resistor on  the In of the VCA circuit should have signal on both sides of it.  The signal splits here and goes to the Side Chain and the VCA.  I have signal on the SC side of the resistor but nothing on the VCA side... however, wouldn't I have to have signal there to be seeing signal at the output?  Otherwise, how would the signal get to the output?  It has to go through the VCA even if no compression is happening.  Am I doing something stupid here?

I've taken the Turbo and HP boards out to simplify troubleshooting.  All the voltages look good.  The threshold pot swings the voltage at Pin 2 of the TL072 from +3V to -3V.  Seems to be working. 

I'm fairly confident that the chips are working... swapping things hasn't changed anything.  Any advice would be awesome.