GSSL HELP THREAD!!!

[Harpo]

sorry I have a strange problem ....
I measured all the voltages and they seem ok except on the side chain VCA pin 5  7.7v instead of 8.7v.
I made measurements without IC and VCA
another question
lorlin switches have a orientation?
thanks

Assuming your -12V rail voltage is working, exchange your wrong 5K6 resistor with a 3K9 resistor, connecting between -12V and pin5 of your not fitted sidechain VCA.
BTW, your voltage readings are missing the - sign. (Keep your black probing wire connected between multimeter COM and 0V from your circuit. Measure DC voltages with red probing wire and you'll get the correct sign positive or negative values.)
Lorlin type switches are symetrical. Place the Lorlin end-stop washer in the correct hole AFTER turning the switch full CCW with end-stop washer out.

 

[ilfungo]

Harpo thanks for your answer
sorry but where is the resistance from 5k6 to 3k9 that I have to replace?
there is a 3k9, perhaps you mean the opposite?
thanks

 

[Harpo]

With all ICs out, sidechain VCA pin5 is at the voltage divider junction 3k9/(10k+47R) between 0V and -12V.
If the 3k9 is a 3k9 for real and your -7.7 voltage reading was correct, the 10k between VCA pins3/5 would be a 6k8 instead.
(For whatever reason a 10k gets mixed up less often, so in my 50/50 chance for a wrong guess I pointed at the 3k9 resistor from previous post).
BTW, with ICs fitted, this voltage reading will be different and VCA pin5 is more current than voltage.

 

[a_)_i]

Hi Folks,

I've been using my 2 GSSLs for a while and they both seem to be showing the same intermittent fault.

Quite often (perhaps 6 or 7 times out of 10) the units will not pass audio after they are first turned on.  After fault finding I have discovered that the +15 rail is measuring -0.76v at the test point, post regulator.  The -15v is fine.  After time passes (around 5-10 minutes) the +15 rail will usually kick in and stay that way with no problems.

I believe that problem occurs at the 7815 (7815CV from what I remember) regulator as it receives voltage (+19v),  yet the output is -0.76v!  I have tried a number of things including using changing the transformer - this one outputs approx 21vac under load.  The same problem occurs though.  The components I have used in the power supply are 63V 1000uF filtering caps and 25V 22uf caps. 

Has anyone experienced this problem?

Any suggestions welcome. 

 

[warpie]

I'm not sure but I think this has been discussed before and it's the actual regulator that causes the problem.
Can't tell for sure though...

 

[danijel]

I've had a similar problem. It was faulty regulator in my case.

Best Regards
Danijel

 

[dustbro]

Has anyone experienced this problem?

I had the same issue. I swapped out the regulator 5 or 6 times, which didnt fix the problem. I also tried the "resistor trick" with the -15V line, and that didnt work either. I finally found a cure by adding in my own variable power supply.
Good luck tinkering with those regulators. Post back if you get it working.

 

[ilfungo]

Hello everyone
I found on an Italian forum a mod to do for your problem ....
the man who is proposing a major designer and manufacturer pro  audio.
I hope you can help
2x 2  100nF\50V ceramic
1 x 1N4007

 

[a_)_i]

Thanks for your replies everyone.  It seems that issue might be more prevalent than I thought! 

warpie - I can't find any previous posts on this problem, please link if you can find one.

danijel & dustbro - I have swapped the regulator out a couple of times - with no effect.  I'm not aware of the -15V resistor trick, please elaborate.

ilfungo - thanks for that suggestion.  Do you have the circuit diagram as well?  I am sure I can work it out from the picture but a cicrcuit diagram would be handy!!!  Has anyone else used this fix?

 

[ilfungo]

"ilfungo - thanks for that suggestion.  Do you have the circuit diagram as well?  I am sure I can work it out from the picture but a cicrcuit diagram would be handy!!!   Has anyone else used this fix?"


no .....
but the site where I found I got more photos to better understand the point
many users of this forum have made this change has solved the problem
I hope it can help

 

[ilfungo]

excuse to learn more look at the photos from last to first ...

 

[ilfungo]

in this forum I also found other uses for those changes That 2180

I made those areas VCA
What can you tell me to serve those in the IN-OUT
thanks

 

[warpie]

Thanks for your replies everyone.  It seems that issue might be more prevalent than I thought! 

warpie - I can't find any previous posts on this problem, please link if you can find one.

Unfortunately, I can't find a link but I remember someone mentioning (maybe Gyraf?) that some specific brand will have issues with the gssl.
Have you tried to use regulators from a different brand?
Again, I might be completely wrong but this is what I remember.

 

[Ayman59]

Hi guys  ;D

I just finished my first gssl (with turbo and crc filter options), I checked voltages and found verry good values for all IC's so I put in OPAMP's and VCA's and turned it on...

Now my problem is that I only ear the left output!!! (I'm earing some cracking sounds when I put threshold to the minimum!?)

I made some test on the connectic and the problem is apparently not there, it comes from the main pcb but I don't know where to look at??
I can locate the right VCA, the ouput, the right opamp,... but that's all, I don't know how to approach the problem??

anybody to give me a direction to look at in here ??

Something else:
I'm using 2180LA VCA's for the moment, what about getting some dbx 202X ?

 

[wahfreak]

HI,
I have a newbie question about the EAO switches. If I use the 01-282.025 part number, I can use these for all three (power, bypass and turbo) switches correct? I would just need to wire them for their particular function.

 

[nashkato]

hi

got an intermittent problem with my Gssl with turbo board.

yesterday it wouldn´t pass audio at all , only a short hum when turning treshold or output into max position.
powersupply voltages read fine.
wanting to trace the problem today , voila , it works as if there was never a problem.
this happend now the second time , the first time it was a loose cable on of the turboboard connectors.

any idea how to manage to find out what the problem might be ?

thanks

 

[a_)_i]

Problem solved with ilfungo's suggested fix involving the 100uf ceramics and 1n4007 diode.  This was also discussed on 177-178 of this thread and is referred to as the GSSL +15v latch-up problem.

thanks guys!

 

[ilfungo]

Problem solved with ilfungo's suggested fix involving the 100uf ceramics and 1n4007 diode.  This was also discussed on 177-178 of this thread and is referred to as the GSSL +15v latch-up problem.

thanks guys!

I'm glad it worked ...

I would like to mount two stacked toroidal
1 - Power-General
2 - + Bypass LED meter relay
can work?
thanks

 

[spica]

I have an issue on the +15V rail that has baffled me for a couple days.  After the 7815, I have +14.8V on power up... but it starts going down to about +6V after about 3 seconds of power on.  This is without any IC's placed on the board.

I've taken the 7815 out of the circuit and tested it and it seems to work alright on its own.  This doesn't seem to be the same issue as the "latch up" problem because it starts out fine.  The -15V, and +/- 12V rails are stable.  I've swapped out the cap after the 7815 and it didn't make a difference... I can't find any solder bridges and all components seem to be correct and ok. 

Can the 7815 be bad in a way that once it sees any kind of load it starts to ramp down the voltage?  Maybe a bad cap somewhere that I can't find?  Solder bridge that I can't find? 

I'm not sure what would cause such a symptom. 

 

[spica]

After further testing I'm a little more confused. 

The voltage seems to be fine coming off the CRC board (+/- 26V ish).  The large caps before the +/- 15 regulators were tested and swapped to no effect.  Thinking the 7815 was bad, I replaced it with a lm317 circuit that behaves fine UNTIL it is actually placed in the circuit with the -15V.  When i use it in place of the 7815 I find a similar phenomena of it starting at an ok voltage and then dropping to around +10V.  What is particularly odd about this is this will happen when I don't have the output of the lm317 connected to anything.  I have the CRC board output coming into the main GSSL board.  I run a wire from the 7815 In pad to the In on the lm317 circuit, connect the ground pad, and do NOT connect the lm317 output back to the board... and the voltage at the lm317 out still drops.

Furthermore, if I connect only the +15V to the board (with the lm317 circuit) and leave off the -15V side, the +15V is fine and stable.  As soon as I connect both +15/-15 regulators the positive side drops.  So, I thought there has to be something wrong between the power input on the board and the regulators.  I already eliminated the rectifier diodes, so I removed the large 1000uF caps between the power input on the main board and the regulators thinking something must be wrong with those... now the +15V is fine and the -15V rail is -12V... If I put one of the caps back on the negative side nothing changes.  Both caps in brings the positive side down and the negative side is fine. 

Any idea what might cause something like this in the circuit?  The only thing I can think of is that this has to do with the interplay of the -15V and +15V on the board which I believe only happens at the VCA distortion trim pots... (I'm actually using fixed resistors there temporarily) but those seem fine and are correct values - 25k+25k-ish per side.


This is all without the switch control board connected and no chips in.