GSSL HELP THREAD!!!

[fucanay]

[quote author="tommypiper"]Hi Matt, thanks, you've cheered me up already. Sorry, I don't have iChat, I'm on a very old Mac...

Counting from the edge of the board, it's the traces connecting to pins 2 and 3 which show continuity under the sidechain VCA.[/quote]

Yeah, I just tested mine and I show it too.

Have you checked the resistor values all around there? Like the 3k9 that leads to the -12 test point? Maybe you have a wrong value there.

Matt

 

[tommypiper]

Thanks. I tested all the resistors when I got the board.

I don't see any 3k9 near the -12v test point. I only see two 10s, near the small regulators.

The 3k9 near the sidechain is testing 3k2 while on the board. I'll pull it off and test it... It tests 3k83 off board.

Can someone help locate the -12v test point on the schematic, and the +15v test point, please?

 

[tommypiper]

Maybe this will jog something. Humor, if nothing else.

Odd voltage readings:
TL074:
pin 1 -.7v
pin 2 -.8v
pins 6 & 7 -.8v
pins 8 & 9 +1.7v
pin 13 -.8v
pin 14 -.5v

TL072:
pin 2 +1.8v
pin 6 +1.5v

Sidechain VCA:
pin 5 -8.8v
pin 8 -8.0v

Output 5532:
pin1 +.9v
pin2 +.6v
pin6 +.9v
pin7 +.9v
pin8 +14.8v

L & R VCAs:
pin3 -15.2v
pin5 -15.2v
pin8 +.7v

These don't look corect to me. Are *any* of them correct?

I'm still getting -20v at the -12v test point on the back of the board. This is the negative lead on one of the 22u caps. Is this actually supposed to be -12 or -20? Can anyone tell me which cap it is on the schematic, please?

 

[fucanay]

I'll be checking everything on my board once my son goes to bed, but I think I've figured this out.

After doing some tracing for you, I believe that the -12 on the back is just identifying the rail, not a test point. If you notice, the negative (-), of the -12V on the bottom of the board, is actually touching the trace that is -12. It connects to pin 11 on the TL074 and the 3k9 resistor in the side chain. It also goes to pin 4 on the TL072. If you're getting that, I'm sure the +/-12V part of the PSU is good.

I'll post my results in a couple hours.

Matt

 

[fucanay]

Are you testing with chips in or chips out?

Matt

 

[fucanay]

Ok, I went in and tested with chips out. I don't know if that's the same as how you did it, but it's the state my board is in right now.

Rails
+14.69
-14.98
+12.02
-12.17

NE5532 Output (channels weren't identical, but close. I'm only writing one down.)

1. 0.44V
2. 0.44V
3. 0V
4. -14.98V
5. 0V
6. 0.44V
7. 0.45V
8. 14.69V

NE5534 Input (channels weren't identical, but close. I'm only writing one down.)

1. 0V
2. 0V
3. 0V
4. -14.98V
5. 0V
6. 0V
7. 14.69V
8. 0V

NE5534 VCA section (channels weren't identical, but close. I'm only writing one down.)

1. 0V
2. 0V
3. 0V
4. -14.98
5. 0V
6. 0V
7. 14.69V
8. 0V

Channel VCAs

1. 0V
2. 0V
3. 0V
4. -0.52
5. -14.97
6. 0V
7. 14.69V
8. 0.44V

TL072

1. -.03V
2. -.03V
3. 0V
4. -12.17V
5. 0V
6. 0V
7. 0V
8. 12.02V

TL074

1. 3.35V
2. 3.35V
3. 0V
4. 12.02V
5. 0V
6. 3.14V
7. 3.14V
8. 0V
9. 0V
10. 0V
11. -12.17V
12. 0V
13. 3.56V
14. 3.84V

Sidechain VCA

1. 0V
2. 0V
3. -0.03V
4. 0V
5. -8.26V
6. 0V
7. 12.02V
8. 3.4V

I hope this helps.

Matt

 

[gyraf]

NE5532 Intput (channels weren't identical, but close. I'm only writing one down.)

1. 0V
2. 0V
3. 0V
4. -14.98V
5. 0V
6. 0V
7. 14.69V
8. 0V

Input opamps are 5534, not 5532!!!

 

[tommypiper]

[quote author="fucanay"]

...I believe that the -12 on the back is just identifying the rail, not a test point.

Matt[/quote]

Thanks, Matt. It would be nice if the maker of this board could verify that or answer this question I have been asking many times.

 

[tommypiper]

Matt, there are many discrepancies between your readings and mine in the chip sockets. (Yes, mine were also done with empty sockets.) You also had discrepancies between left and right, which makes me wonder what those small voltage readings mean, if anything?

My TL074 has many discrepancies:
Pins 1,2,5,6,7,13,14.

Your board is working, right? So I should be trying to get the same values?

 

[tommypiper]

[quote author="gyraf"]

NE5532 Intput (channels weren't identical, but close. I'm only writing one down.)

1. 0V
2. 0V
3. 0V
4. -14.98V
5. 0V
6. 0V
7. 14.69V
8. 0V

Input opamps are 5534, not 5532!!![/quote]

OUCH!

Jeez, he just made a typo, for crying out loud. We know what he meant. He's trying to help.

 

[fucanay]

[quote author="gyraf"]

NE5532 Intput (channels weren't identical, but close. I'm only writing one down.)

1. 0V
2. 0V
3. 0V
4. -14.98V
5. 0V
6. 0V
7. 14.69V
8. 0V

Input opamps are 5534, not 5532!!![/quote]

Ah Ha, But you'll notice that I wrote "Intput" so I am only half wrong. Hmm, maybe even more wrong. Anyway, I fixed it in the list.

Matt

 

[Greg]

[quote author="tommypiper"](Yes, mine were also done with empty sockets.)[/quote]
The regulators need to be loaded to test for proper voltages ! As long as you aren't measuring any shorts get those chips in there !

 

[tommypiper]

Hi Greg, thanks! Nice to get an answer on here from someone.

The last time I powered it up with chips it blew up one of the 55xx chips. Nasty pop, hiss, lots of acrid smoke...

 

[tommypiper]

OK, Matt, that was helpful to compare readings. A couple curious points:

The schematic shows the VCA 5534s with + / - 12 on pins 7 & 2. However, both our boards are showing + / - 15 on those pins. Anyone?

Likewise, the schematic shows + 15v on the THAT pin 7, but both you and I measured +12v. Which should it be?

Neither you nor I had a corresponding -12 or -15 on any THAT pin. The schematic shows -15 on pin 2. Do we have the same problem? Anyone?

My output 5534s show only +.7v on pin 7 where I expect +15. That is clearly wrong. And maybe why the previous 5532 exploded. I'll work on that problem, but I don't know what to make of the previous points. Anyone? Mr. Gyraf, can you clarify what the correct readings should be?

 

[fucanay]

[quote author="tommypiper"]OK, Matt, that was helpful to compare readings. A couple curious points:

The schematic shows the VCA 5534s with + / - 12 on pins 7 & 2. However, both our boards are showing + / - 15 on those pins. Anyone?

Likewise, the schematic shows + 15v on the THAT pin 7, but both you and I measured +12v. Which should it be?

Neither you nor I had a corresponding -12 or -15 on any THAT pin. The schematic shows -15 on pin 2. Do we have the same problem? Anyone?

My output 5534s show only +.7v on pin 7 where I expect +15. That is clearly wrong. And maybe why the previous 5532 exploded. I'll work on that problem, but I don't know what to make of the previous points. Anyone? Mr. Gyraf, can you clarify what the correct readings should be?[/quote]

The only voltage I would compare to the schematic is the +/- 12 and 15 until the chips are in. I'm going to be on this tonight or maybe get off work a bit early and go for it this afternoon. It's really almost done, so I just need to wire up a few things and give it a test try.

I think you should also take into account that I have changed resistor values around the channel VCAs to account for the THAT 2181LB chips I'm using. So the voltages may be slightly off compared to your anyway. I dunno.

Matt

 

[gyraf]

The schematic shows the VCA 5534s with + / - 12 on pins 7 & 2. However, both our boards are showing + / - 15 on those pins. Anyone?

Yes, the VCA's drivers has been moved to +/-15V lines. Haven't updated schematic (this is an oooold change)

Jakob E.

 

[fucanay]

Ok, I messed up on the board I checked. These are not yet finished either and I have been making some of the changes that were based on the THAT datasheet. Some of them are apparently not correct because I thought I was supposed to remove one of the 10K resistors and not put a jumper in. But that makes some of the points have no voltage on the channel 5534 sockets. I had one board one way and another board the other way.


So now it reads like this.

Ok, I went in and tested with chips out. I don't know if that's the same as how you did it, but it's the state my board is in right now.

Rails
+14.69
-14.98
+12.02
-12.17

NE5532 Output (channels weren't identical, but close. I'm only writing one down.)

1. 0.44V
2. 0.44V
3. 0V
4. -14.98V
5. 0V
6. 0.44V
7. 0.45V
8. 14.69V

NE5534 Input (channels weren't identical, but close. I'm only writing one down.)

1. 0V
2. 0V
3. 0V
4. -14.98V
5. 0V
6. 0V
7. 14.69V
8. 0V

NE5534 VCA section

1. 0V
2. -14.98V
3. 0V
4. -14.98
5. 0V
6. -14.98V
7. 14.69V
8. 0V

That looks better.

Matt

 

[tommypiper]

Big Thanks to Matt. :guinness:
We both got our units running and passing audio. :grin: Mine is not compressing. In case anyone knows, mine doesn't have the bypass switch wired in (I'm looking for a switch in meantime), would that be the reason it's not compressing?

 

[tommypiper]

Jacob, or anyone. My last +15v regulator was actually putting out -1v for about 30 minutes before I tracked down the problem. Could I have damaged any of the caps or chips during that period?

My question is, should I worry about damaged components from it having run with -15v and -1v on the power rails?

Second question. No compression. I do not have the bypass switch. Will the compression work without it? What do I need to do?

The switches are wired backwards in orientation from the board. Could that be a problem? (I didn't wire them, so it's a mystery to me.)

It passes clean audio but does not compress.

 

[tommypiper]

I'm stuck. I spent two days reading this help thread over and over and took 15 pages of notes.

I am trying to trace the signals, but I don't understand everything. I have traced backwards from the VCAs where there is no signal and finally found a small AC signal on Pin 6 of the Input 5534, but I am confused about where it goes next. I can find the signal on the upstream side of the 27k resistor, but not on the dowstream side, there it disappears.

(Both channels are doing this, so I don't think it's a bad resistor. Furthermore, both channels are outputting audio, so the signal is passing beyond this point in the audio path through this resistor, if I understand correctly.)

I don't understand why the traces are leading into the VCAs there, when the schamaitc says it's going to the sidechain, and yet how is it getting to the output if there is no signal in the VCAs? :sad: :?:

Am I looking for an AC signal (audio)? Like .03v?

Is this the correct way to look for no compression problems?

The unit passes audio and makeup gain works, but no compression.