GSSL HELP THREAD!!!

[scott2000]

Hi everybody .
it's been 17 years since last post on this thread...
...

I'm having a look at a ssl-clone-comp that i bought some years ago.
I haven't used it yet,
but would like to, now.

I have that hum problem, and would love to get rid of it.

Here are some pictures.
The rear side of main PCB has been adapted, that's obvious...

Would anyone have anything to say about the way transformer has been soldered ?

Thanks, very much, for your help

Mat

I moved this for you...

Some janky looking stuff going on in that transformer area. I'm not familiar with this project so maybe normal stuff. Some of those through hole blow outs look suspicious and I would verify circuit continuity where it should be...
The xlr connectors look funky . Any chance for some less blurry pics of the wiring there?

 

[tactyl]

Hi!
So, i started the GSSL project about a year ago, as a project to do from time to time. Power transformer rated: 17.5-0-17.5v, VCA: 2181A pre-trimmed. I "finished" it somehow but i have some problems:
1- first time powering up, hooked up to my soundcard: some huge hum, no sound passing. I checked the GSSL thread, corrected the ground to the xlr pin 1 to chassis, turned arround the toroidal. Opened back the comp, the hum was gone, still no sound passing.
2. I removed all the chips from the pcb and started to measure. I got the following:
a)- LM7915: in- 38.76v, out: 15.09v- getting hot, normal i suppose...
b)- LM7815: in- 6.3v, out: 0.002- not good, i suppose
c)- Op-Amps:
- NE5534: pin4- -15v, pin6- 0v, pin7- 4.87v, pin8- 2.7v.
- NE5532: pin4- -15v, pin6- 0v, pin7- 0.05v, pin8- 4.8v (sometimes rising to 8.5).
d)- TL072: pin4- -12v, pin8- 3.43v
e)- Traces to VCA: right VCA- -15v, left VCA- 6v
I read that LM7815 is hard to kill, so i checked for cold soldering, it is not the case, as it's well soldered.
Also, before assembly and turning the unit on, i checked about 4 times for bad soldering, cold soldering, soldering joints. It was all good, otherwise I would not have powered the unit.
I'm thinking about changing the LM7815, but I don't know what caused it to stop working, I don't know what to do next, what to look for...
Can you point me to the right direction, please?
TIA!

 

[Script]

We can only guess.
- regulator latching
- exotic switches with LED wired wrong
- IC inserted with wrong orientation
- solder bridge
etc etc

As a rule, always measure voltages at sockets first before inserting any IC. If you used IC sockets, can still do.

 

[tactyl]

No LED's on switches. Lorlin switches, IC's are good oriented - triple checked, confronted with other pictures in this thread.
No solder bridges, also checked 4 times.
I'm thinking about swapping the regulator, and do a second round of measurements.
As for the switches, it matters so much the wiring? For example, i have Lorlin switches as i mentioned above, but for dual poles i have A-C, not A-B as stated on the schematics. Of course i wired it by poles, also keeping the numers as by schematics. Should this be a problem?

 

[Harpo]

... Power transformer rated: 17.5-0-17.5v,...
a)- LM7915: in- 38.76v, out: 15.09v- getting hot, normal i suppose...
b)- LM7815: in- 6.3v, out: 0.002- not good, i suppose...

A 35VAC center tapped power transformer with primary winding hooked up for your romanian local 230VAC mains (primary winding(s) hooked up correct?) most likely ist not producing 38.76VDC in front of your voltage regulator. After rectification (VAC*1.414 - about 2*0.6V diode drop in rectifier) that would be an unlikely 60% regulation of an unloaded transformer on top to give out 38.76VDC (as well as exceeding the abs.max. 35VDC input voltage of the LM7x15 regulator). In respect to what exact spots did you measure your stated voltages (and are these AC or DC and signs matter).

 

[tactyl]

A 35VAC center tapped power transformer with primary winding hooked up for your romanian local 230VAC mains (primary winding(s) hooked up correct?) most likely ist not producing 38.76VDC in front of your voltage regulator. After rectification (VAC*1.414 - about 2*0.6V diode drop in rectifier) that would be an unlikely 60% regulation of an unloaded transformer on top to give out 38.76VDC (as well as exceeding the abs.max. 35VDC input voltage of the LM7x15 regulator). In respect to what exact spots did you measure your stated voltages (and are these AC or DC and signs matter).

Yes!
I have the following:
Transformer: 2x 115, connected together midle windings so I have 230V AC primary. In secondary: I have 17.5v- 0v- 17.5v, 530 mAh- AC.
I measured the voltages with 0V from audio input side, DC current- I read that on the thread also.

 

[gyraf]

b)- LM7815: in- 6.3v, out: 0.002- not good, i suppose

Could the +15V line possibly be shorted to ground? Check with an ohm-meter

If not, note that 7815 is supposed to have some +25V to +35V on it's input

/Jakob E.

 

[tactyl]

Could the +15V line possibly be shorted to ground? Check with an ohm-meter

If not, note that 7815 is supposed to have some +25V to +35V on it's input

/Jakob E.

I've checked all good! I will check again. Thank you!

 

[Harpo]

Yes!
I have the following:
Transformer: 2x 115, connected together midle windings so I have 230V AC primary. In secondary: I have 17.5v- 0v- 17.5v, 530 mAh- AC.
I measured the voltages with 0V from audio input side, DC current- I read that on the thread also.

Pinout of LM7815 and LM7915 is different. From your -38.76VDC and +6.3VDC numbers (assuming sign) that's a total of 45VDC in between rectifiers +/-nodes with 0VDC reference voltage in between, would be a more reasonable +/-22.5 VDC at each input of the voltage regulators. There might be a broken or misplaced/wrong orientation chip pulling the +15VDC rail down. Pull all opamps and VCAs and confirm voltage readouts of +/-15VDC supply rails again. A once powered opamp or VCA placed with wrong orientation will not have survived.

 

[tactyl]

Here are some pictures of my pcb. I hope it can be seen the orientation of IC's. Partially before and after...
Maybe i've done some stupid things, i wouldn't say no , but for every step i did, i calculated my moves and read a lot, as I really like this comp.
For example, underneath the pcb there is a piece of rubber to insulate from the case.
Also, i isolated most of the wires, although it is just for testing mounted.
If I understood right what Harpo said, I'm starting to believe that the trafo is too big (?!) and burned my regulators...
I bought 4 sets of those today (negative and positive also ), i will replace them and order a new toroidal.
I will order a custom one soon as I have near me a business that make custom toroids, so if you have any suggestions, I'm more than grateful:
- voltages (15-0-15?)
- current- thinking about 2 Amps (?), as i will try to add later some turbo, SCC and a vu-metter card
Do you have other suggestions regarding my situation?
Thank you!

 

[monsieur yumels]

Hello!

Do I have to replace tantalum capacitors of sidechain timing section if placed with reversed polarity? Should I change the TL074 because of this too? The 24Vdc supply for TL074 are stable.
Thanks!!

 

[Script]

2181A pre-trimmed

Aren't the THAT2180 pre-trimmed, while the 2181 are trimmable? Should still pass audio though, I guess.

 

[tactyl]

Aren't the THAT2180 pre-trimmed, while the 2181 are trimmable? Should still pass audio though, I guess.

I read that THAT2181 are also pre-trimmed. And even if it weren't, as you said it should've passed audio...