GSSL HELP THREAD!!!

[djfatum]

Hey Guys, I´m new to the forum and was wondering if you could help me with a problem that I can´t find a reason for.
I´m building the New GSSL, I have it all completed but ran into two little problems.

1. The bigger one:
When I switch on the power on the compressor the first time of plugging in, the gain reduction meter starts to show about 8-12 dB of reduction without any audio going into it. The LEDs in the meter do not light up and the compressor does not work.

BUT, and this is a big but, when I switch it off, the LED will flash after about one second (when the meter falls back to zero), and when I turn the compressor on again, it works just fine.

I find this very strange. The compressor will do this every 2nd time I turn the power on - which means that I have to turn it on and off once before I can turn it on and make it work.

Do you guys have an idea what could cause this problem?

Thanks a lot for your help in advance!!!

Martin

I have the same problem as Martin 

 

[thomasdf]

I was wondering: is it easy to add the autofade function just like the original SSL comp (switch + rate) to that kit?
From time to time it's a pretty useful feature..
Thomas

Ok got my answer after having a closer look at the SSL central section's schematics. The autofade is a different circuit that can be cloned I guess and that is placed before the comp... Maybe it would be a good idea to place it after the compression so the gain reduction remains the same while fading out?

 

[Harpo]

Hey Guys, I´m new to the forum and was wondering if you could help me with a problem that I can´t find a reason for.
I´m building the New GSSL, I have it all completed but ran into two little problems.

1. The bigger one:
When I switch on the power on the compressor the first time of plugging in, the gain reduction meter starts to show about 8-12 dB of reduction without any audio going into it. The LEDs in the meter do not light up and the compressor does not work.

BUT, and this is a big but, when I switch it off, the LED will flash after about one second (when the meter falls back to zero), and when I turn the compressor on again, it works just fine.

I find this very strange. The compressor will do this every 2nd time I turn the power on - which means that I have to turn it on and off once before I can turn it on and make it work.

Do you guys have an idea what could cause this problem?

Thanks a lot for your help in advance!!!

Martin

I have the same problem as Martin 

What's so wrong with reading the answers from pg. 301, 302, 303, just to name a few, to fix voltage regulators hanging on startup ...

 

[Dissler89]

Turned my Circuit on today for the first time after completing the build. (Was waiting 2 months on the last few pieces)
It seemed fine at first. But after a couple of seconds it started to emit a strange smell and a little smoke. Turned it off straight away.
Because this is my first real electronic build I'm not quiet sure where to start with the problem searching. So I'l just post what I observed from the little time I had;

Some of the capacitors were getting hot, mainly near the Diod's and the rectifier.

The + and - 15v rails were fine.

The 12v/relay light supply was fine too.

Thats all I know so far..

Any recommendations as to what might be the fault. Or a simple problem searching advice would be appreciated.

*UPDATE*

After some checking I noticed that my first secondary and my second secondaries had contact with one another on the board.
Bad soldering. I'm guessing this was the reason which has led to most of my resistors drop in value and my capacitors being dead.
Luckly I didn't have any chips in the circuit yet. But I'm assuming I'l be having to replace most of the parts...

Am I right in thinking that this might have been the main mistake I made?

*Update*

Seems to be working fine now :S nevermind.

 

[tabuckner]

Hello All,

I have made substantial progress on my build however I am still having an issue with getting the unit to maintain a steady threshold. The unit will compress momentarily if I turn the threshold knob or adjust the other rotary switches on the control board.

Here is the link to a video detailing the units strange behavior:
**Note: this video was made earlier today prior to changing out the voltage regulators for Fairchilds**
http://youtu.be/TB4bDwtBtIc

Here is a link to some images detailing my build that might lend some help:
http://imgur.com/a/gDRxJ#0
I have triple checked the wiring of the bypass switch as suggested by some here in the forum and by Gustav when I spoke with him. However, we have concluded that there is no issue in the bypass switch's wiring.

I have also replaced all ICs and voltage regulators with TI chips and Fairchild regulators respectively. I happened to have some of the components lying around at work and was able to shell out a few extra bucks for some replacement chips in the off chance that the issue I am having lie in that aspect of the circuit.

Here is a rundown of the voltages I am reading on the oscilloscope with the unit powered on and stable with no input signal:

**Voltage Regulators**

7812
Input: 28.2v
Output: 12.1v

7815
Input: 26.4v
Output: 15.2v

7915
Input: -27.9v
Output: -15.2v

78L12
Input: 14.4v
Output: 12.4v

79L12
Input: -14.9v
Output: -12.2v

**Op Amps**

5534 (same values for all ICs in series)
Pin 4: -15.2v
Pin 7: 15.2v

5532 (same values for all ICs in series)
Pin 4: -15.2v
Pin 8: 15.1v

TL072
Pin 4: -12.2v
Pin 8: 12.4v

TL074
Pin 4: 12.4v
Pin 11: -12.2v

2180B

{Left}
Pin 5: -2.75v
Pin 7: 15.1v

{Right}
Pin 5: -2.7v
Pin 7: 15.1v

{Sidechain}
Pin 5: -2.7v
Pin 7: 12.4v

I have already replaced the TL074 and TL072, as well as the two 5534s in the VCA circuits.

I'm at a complete loss as to why the unit is not functioning properly and I am on an extreme time crunch.

Details on components used:
2x18 Triad Trafo
8027-B meter (LEDs powered via 12v rail and voltage dividers)
Everything else is from the kit ordered from the very helpful gentleman, Gustav at PCBGrinder.com

 

[gyraf]

Have you mounted the sidechain-hpf-jumper?

 

[tabuckner]

Yes sir, I have. I have the outer two connections shorted with a jumper, however I've been informed that all three holes might need to be shorted. Is this in fact correct?

Here is a link to a picture that indicates my current configuration for the HPF jumper:
http://imgur.com/a/gDRxJ#5
and
http://imgur.com/a/gDRxJ#6

Thank you very much in advance,
Taylor A.

 

[Dissler89]

So I've checked the voltage rails and their at 15V +/- now along with the 12V +/- supply and everything seems fine.

I've re-measured some of the components straight from the board, some of which have changed slightly..  e.g. some 20K resistors have gone down to 15K  :-\. This can't be normal can it?or is the measurement invalid because I'm taking it straight from the board rather then detaching one end of the resistor and taking the measurement?

If this is not an issue (which it probably is) I'm assuming the next procedure would be to implement the chips?
Or should I first check the Vcc voltage supply of the housing for the chips before attaching them?
Stupid question. I'l check the voltages against the schematic relative to the chips. and go from there.

Wisdom guidance appreciated. First electronic build.

 

[ding]

Hello all,

I have a slight situation with my GSSL build. I am building a Rev. 4 that I got from a forum member with the ICs (except the THAT2180s) and a few caps and resistors already soldered on. Well, I finished it up measured all voltages on all ICs and regulators and they measure good. The unit seems to be functioning normally except for one crucial thing. I have to send it very, very and I mean very low levels or else it will distort like crazy. I also need to put my interface input on Hi-Z or it will also distort. By distort I mean to me it sounds like the opamps are clipping. For a while I thought I was doing something wrong with my interface routing, and I am not ashamed if that turns out to be the case but I find it unlikely. Could this be the fault of the input or more likely output ICs? I checked my XLR connections and they are fine, exept I havent soldered on pin 1 to ground but that should not matter for this problem. I am using the 2180As with the mods from Matt over here... http://diy.fischerworks.com/gssl_vca.shtml except I am using 27k resistor instead of 15k by the VCAs. I did not test the soldered on components since I would have had to unsolder them->test them->solder them back on. I have all the SSC and turbo and things but have not installed them until I get this vanilla GSSL up and running properly. Any ideas where to continue troubleshooting this problem?

Thanks,
Alain

 

[Harpo]

I have to send it very, very and I mean very low levels ...

that would be a measurable AC voltage, so we get your idea of very low ...

or else it will distort like crazy.

No surprise with at least the two wanted 5K1 resistors connecting to audio-VCAs pin 5 being 51K and the wanted 3K9 resistor connecting to sidechain-VCA pin 5 being 51K.
There might be more ...

 

[Harpo]

I've re-measured some of the components straight from the board, some of which have changed slightly..  e.g. some 20K resistors have gone down to 15K  :-\. This can't be normal can it?or is the measurement invalid because I'm taking it straight from the board rather then detaching one end of the resistor and taking the measurement?

Yes. Most often there are other components in parallel or series/parallel to the measured part when measuring in circuit.

 

[Gustav]

No surprise with at least the two wanted 5K1 resistors connecting to audio-VCAs pin 5 being 51K and the wanted 3K9 resistor connecting to sidechain-VCA pin 5 being 51K.
There might be more ...

Eagle eyes Harpo!!!

Gustav

 

[Harpo]

I am still having an issue with getting the unit to maintain a steady threshold. The unit will compress momentarily if I turn the threshold knob or adjust the other rotary switches on the control board.

Are the not shown pots wired correctly with your green wires ? Mixing up an outer and wiper connection at the pot will shunt down one of the +/-12V rails (and hereby probably damage the pot).
Do the +12V and -12V rails hold their voltages when you turn the pots ? The vregs most often will give out normal voltage again when coming back from self protection mode after fault condition is cleared.

8027-B meter (LEDs powered via 12v rail and voltage dividers)

LEDs powered via 12v rail and a single current limiting resistor per LED.

 

[ding]

that would be a measurable AC voltage, so we get your idea of very low ...

;D

No surprise with at least the two wanted 5K1 resistors connecting to audio-VCAs pin 5 being 51K and the wanted 3K9 resistor connecting to sidechain-VCA pin 5 being 51K.

must have gone a little 51k crazy, I guess I couldn't resist -^v^-. 
Thanks Harpo you are the man. Serious eagle eyes. Will re-place/re-test.

BTW the silkscreen for rev 12 says that you need a 5k1 on the sidechain VCA. Is that correct? I am a little confused since the schematic says 3k9 for both the audio and sidechain VCAs.

 

[Harpo]

BTW the silkscreen for rev 12 says that you need a 5k1 on the sidechain. Is that correct? I am a little confused since the schematic says 3k9 for both the audio and sidechain VCAs.

5K1 resistors connecting to pin 5 of the +/-15V powered audio-VCAs,
3K9 resistor connecting to pin 5 of the +/-12V powered sidechain-VCA.

 

[tabuckner]

I am still having an issue with getting the unit to maintain a steady threshold. The unit will compress momentarily if I turn the threshold knob or adjust the other rotary switches on the control board.

Are the not shown pots wired correctly with your green wires ? Mixing up an outer and wiper connection at the pot will shunt down one of the +/-12V rails (and hereby probably damage the pot).
Do the +12V and -12V rails hold their voltages when you turn the pots ? The vregs most often will give out normal voltage again when coming back from self protection mode after fault condition is cleared.

I followed the literature provided on Gustav's site but I suppose it's possible that I mirrored the Threshold pot. I'll test the 12v Rails when I get off work and post my findings.

Correct me if I'm wrong, but if I wired the pot incorrectly I should see the +12V and -12V rails not holding a steady voltage when I turn the pot. Am I understanding you correctly?

8027-B meter (LEDs powered via 12v rail and voltage dividers)

LEDs powered via 12v rail and a single current limiting resistor per LED.
[/quote]

Oops, my mistake.  Thought tapping the center of two equal value resistors would result in half the voltage on the input side. But you've yet to steer me wrong, so I'll trust you! Thanks for catching that, Harpo!

 

[Harpo]

..but I suppose it's possible that I mirrored the Threshold pot.

Not what I wrote. Mirroring the outer pot connections would only exchange the CW and CCW end. Mixing up the wiper connection with FI any of the makeup pots outer connections will short out the +12V regulator when the wiper (the pots center pin) is turned towards the other connected rail.

Correct me if I'm wrong, but if I wired the pot incorrectly I should see the +12V and -12V rails not holding a steady voltage when I turn the pot. Am I understanding you correctly?

Would be the consequence for the +12V and/or -12V rail and hereby killing your wrong connected pot if not already done, if this was the reason for misbehaviour. The pots resistive trace is not built for this amount of current running thru and will burn up, so check wire connections before powering on again. Maybe your pot(s) survived up to now. None of your pics shows the relevant part of described scenario and parts values are not to identify.

Thought tapping the center of two equal value resistors would result in half the voltage on the input side.

LEDs are current operated devices. [(Supply voltage - LEDs forward voltage drop)/amount of current in A you allow for to not build a headlight=value of current limiting resistor needed in ohm]. The amount of current you allow for flowing thru the LED must not exceed parts rating and lesser current gives dimmed result. If your meter has more than one LED inside, multiply the amount of LEDs forward voltage drops by the number of series connected LEDs inside. FI (12V-2*2.0V)/0.01A=800ohm, so maybe pick a 820R. Min.resistor rating needed for this two red LEDs inside example is (12V-2*2.0V)^2/820R=0.078W, so doubling up the min.required wattage, a 1/4W rating will be sufficient. This LEDs Vfwd varies depending on LEDs colour.

 

[tabuckner]

Ah I see, I misread you post--should have slowed down and read thoroughly.

I'm fairly certain that I would not confuse a wiper and either pole of the pot. Also I'm fairly certain that I connected the pot properly.

I'm going to go ahead and measure the voltages at the rails anyways to be absolutely certain that there is no fault. Additionally, I will take a couple pictures and label them for you. I feel that it is the least I can do for all of your help.

Do you have any other advice for potential causes?

 

[Dissler89]

I took some measurements and I'm not entirely sure of them :-\. Could someone correct me if I'm wrong or give me some insight?
These are measurements taken without the 'Chips' in place.

15V and 12V rails are fine.

7815 Input: +23 <--- Shouldn't this be +15V?
7815 Output: +15

7915 Input: +23  <--- Shouldn't this be +15V?
7915 Output 8.2  <--- Shouldn't this be -15V?

7812 Input +23  <--- Shouldn't this be 12V?
7812 Output +12

Right VCA
2181 Pin 7 15V
2181 Pin 5 -15V

5534 Pin 7 15V
5534 Pin 4 -15

Left VCA
2181 Pin 7 15V
2181 Pin 5 -15V

Input Left
5534 Pin 7 15V
5534 Pin 4 -15V 

5532 Pin 4 +14.97
5532 Pin 8 - 15.06

Input Right
5534 Pin 7 +15V
5534 Pin 4 -15V 

5532 Pin 4 +14.97
5532 Pin 8 - 15.06


TL074 Pin 4 +12
TL074 Pin 11 0V  <--- Shouldn't this be -12V ?

Side Chain VCA
THAT 2181 Pin 7 +12V
THAT 2181 Pin 5 0V

I will double check the measurements tonight.

In the mean time I will run through this thread looking for answers~

 

[Harpo]

7815 Input: +23 <--- Shouldn't this be +15V?

would be a problem if it would read +15V. The fixed voltage regulators need some exess voltage at input to regulate down to their stated output voltage. If input is below this dropout voltage, the vreg doesn't regulate.

7915 Input: +23  <--- Shouldn't this be +15V?

same as previous answer, but with negative sign. (you keep your black wire probe at your multimeters [com] terminal with probe tip pointing at or croko-clipped to 0V reference voltage. You probe around with your red wire probe for the points under test.)

7915 Output 8.2  <--- Shouldn't this be -15V?

indeed and it obviously is when -15V arrive at fi pin4 of the NE5534s and NE5532s.

7812 Input +23  <--- Shouldn't this be 12V?

same as previous answer for this not audio related aux.supply rail.

5532 Pin 4 +14.97
5532 Pin 8 - 15.06

you mixed up pins 4/8.

TL074 Pin 11 0V  <--- Shouldn't this be -12V ?

yepp. There might be a short somewhere along the -12V rail or at the 79L12.