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I’m Diagnosing SSL Compressor Issues - Please Advise (SSL, GSSL,etc. Rack Compressor)
Old 24th January 2019
  #1
I’m Diagnosing SSL Compressor Issues - Please Advise (SSL, GSSL,etc. Rack Compressor)

Hi GSers - Diagnosing my original FX-G384 Grey Face with THAT 2002T VCAs and LF356N ICs.

I'm hoping some here may take pity on me and offer some suggestions, any suggestions on troubleshooting and diagnosing this G384...

-Originally the issue started with an intermittent short in the right channel that seemed to be affected by turning the ratio switch...
-Though now, and maybe through my troubleshooting, the Compressor does not seem to engage.

I have done extensive testing, please see results...

Again, Any and all feedback and advice is welcome...I've been pulling my hair out and testing for weeks...Trying to finish mixing a labor of love before I run out of money and time and this is my mix bus compressor.

Sincerely,
Attached Thumbnails
I’m Diagnosing SSL Compressor Issues - Please Advise (SSL, GSSL,etc. Rack Compressor)-continuity_test_1_both_channels_same_1-24-19.jpg   I’m Diagnosing SSL Compressor Issues - Please Advise (SSL, GSSL,etc. Rack Compressor)-right_channel_in_and_out_voltage_readings.jpg   I’m Diagnosing SSL Compressor Issues - Please Advise (SSL, GSSL,etc. Rack Compressor)-left_channel_in_and_out_voltage_readings.jpg   I’m Diagnosing SSL Compressor Issues - Please Advise (SSL, GSSL,etc. Rack Compressor)-right_sidechain_channel_voltage_readings.jpg   I’m Diagnosing SSL Compressor Issues - Please Advise (SSL, GSSL,etc. Rack Compressor)-updated_left_sidechain_ic_voltages_1-31-19.png  

Attached Files
File Type: pdf GBUS CIRCUIT DESIGN.pdf (862.3 KB, 17 views) File Type: pdf Main Card Voltage and IC Test Results.pdf (1.58 MB, 14 views)
Old 24th January 2019
  #2
100 View and Nothing? Aww...come on...

100 View and Nothing? Aww...come on...HELP....
Old 27th January 2019
  #3
Old 27th January 2019
  #4
Here for the gear
 

Sorry - beyond me. You'd probably do better posting this at GroupDIY. And you might want to extract your measurements to text - those images are hard to read.

Cheerz,
John
Old 27th January 2019
  #5
Lives for gear
 

I feel that to help at all I need to deconstruct your original post...

For starters, let's not call this a "short" unless we're certain that's the case. A short is an unintended connection between two circuit points. That MIGHT be what's going on here, but it might not be. The issue could also be a broken solder connection, intermittent connector, faulty component, etc.

Unfortunately, all those continuity tests and notes are pretty much useless. Unless you've already narrowed the fault down to a particular circuit area and have a specific troubleshooting strategy in mind, resistance and continuity checks like that will just give random, confusing results that don't really reveal anything.

The next problem is that in your description, you didn't tell us anything about the symptoms. Does the right pass audio but not compress? Is the right output completely dead? Does the channel compress but in the wrong way? Are you hearing noises? Without a clear description of the symptoms, it's impossible to offer specific advice.

Also: these units can be tricky to service!

If you're not experienced in troubleshooting and don't really know how the circuit elements work, I think your best bet is to focus on your original clue, which was a good one -- the fact that turning the ratio switch made the problem come and go at one point. Visually inspect the switch and the circuit elements related to it. Look for a broken wire or a physical short. Look for questionable solder connections on the PCB or maybe a cracked resistor. Clean the switch and see if anything improves.

If that goes nowhere and you want to press on, then study the circuit and try to learn more how the audio and side chain sections work. With the two channels set up the same way and the good channel compressing, methodically compare audio (AC) and side chain (DC) voltages at opamp output pins on the two channels. If the right is totally dead, look at the audio sections. If compression is dead or working incorrectly, look at the side chain sections (which are more complex and difficult to troubleshoot).

Last edited by David Kulka; 27th January 2019 at 09:01 PM..
Old 27th January 2019
  #6
Quote:
Originally Posted by David Kulka View Post
I feel that to help at all I need to deconstruct your original post...

For starters, let's not call this a "short" unless we're certain that's the case. A short is an unintended connection between two circuit points. That MIGHT be what's going on here, but it might not. The issue could be a short, but could also be a broken solder connection, intermittent connector, faulty component, etc.

Unfortunately, all those continuity tests and notes are pretty much useless. Unless you've already narrowed the fault down to a particular circuit area and have a specific troubleshooting strategy in mind, resistance and continuity checks like that will just give random, confusing results that don't really reveal anything.

The next problem is that in your description, you didn't tell us anything about the symptoms. Does the right pass audio but not compress? Is the right output completely dead? Does the channel compress but in the wrong way? Are you hearing noises? Without a clear description of the symptoms, it's impossible to offer specific advice.

Also: these units can be tricky to service!

If you're not experienced in troubleshooting and don't really know how the circuit elements work, I think your best bet is to focus on your original clue, which was a good one -- the fact that turning the ratio switch made the problem come and go at one point. Visually inspect the switch and the circuit elements related to it. Look for a broken wire or a physical short. Look for questionable solder connections on the PCB or maybe a cracked resistor. Clean the switch and see if anything improves.

If that goes nowhere and you want to press on, then study the circuit and try to learn more how the audio and side chain sections work. With the two channels set up the same way and the good channel compressing, methodically compare audio (AC) and side chain (DC) voltages at opamp output pins on the two channels. If the right is totally dead, look at the audio sections. If compression is dead or working incorrectly, look at the side chain sections (which are more complex and difficult to troubleshoot).
Thanks David - Sadly I don't have a working side I don't believe any longer... I don't believe the compressor is engaging at all.

I've "shotguned" with checking and re-soldering...

You see my tests above...I'd send it off if I could but running out of money and trying to finish a labor of love before getting back to the grind.

Any help, advice would be appreciated on next steps...

Sincerely,
Old 27th January 2019
  #7
Lives for gear
 

You still haven't really explained the symptoms clearly...not sure what you mean by engaging. Do the two channels pass audio but not compress? (No offense but I'll never understand why it's so hard to get clear problem descriptions from people seeking help here.)

If the other side went down in the midst of your work then you'd need to go back and re-check your previous steps. Look for solder splashes, broken foils, etc. Check the power supply voltages.

Failing that, if you want to continue, my only advice is what I wrote at the end of my previous post...learn more about the way the audio and side chain sections work, and slowly, methodically trace the signals from start to finish. That might be a big learning curve and may not be worth your time, but I'm not sure what else to suggest. Hope it works out.

I came back from a job in Atlanta last week. The BBQ was great (as always) but dang, it was freezing when we drove to the airport on Sunday!
Old 28th January 2019
  #8
Quote:
Originally Posted by David Kulka View Post
You still haven't really explained the symptoms clearly...not sure what you mean by engaging. Do the two channels pass audio but not compress? (No offense but I'll never understand why it's so hard to get clear problem descriptions from people seeking help here.)

If the other side went down in the midst of your work then you'd need to go back and re-check your previous steps. Look for solder splashes, broken foils, etc. Check the power supply voltages.

Failing that, if you want to continue, my only advice is what I wrote at the end of my previous post...learn more about the way the audio and side chain sections work, and slowly, methodically trace the signals from start to finish. That might be a big learning curve and may not be worth your time, but I'm not sure what else to suggest. Hope it works out.

I came back from a job in Atlanta last week. The BBQ was great (as always) but dang, it was freezing when we drove to the airport on Sunday!
Right on...Fair enough, and it has been cold here David...

Yes the two channels pass audio but no compression...Learning curve indeed but I've spent weeks troubleshooting and sending it off is not an option at the moment.

I've covered your previous suggestions already...and I understand folks like you are indeed doctors...I'd be happy being a pretty good mechanic, just trying to "fix the car" so I can get back to work.

I know decades of learning can't be boiled down, or maybe some of it can...

I've built audio probes, and took as many in circuit reading as I can think of...

I purchased a basic scope and probes and have started taking AC coupled readings with it...and a 1k wave pumped into the compressor...

I believe this is where I need a little direction? I am not 100% Clear on what I'm looking for with the Scope? Please advise?

Am I looking for variations in Mhz or Voltage while in AC Coupling with a scope?

That's my one question David, I am happy to desolder and test components at this point, I've been troubleshooting several things for the last few weeks and am just trying to finish a labor of love before I run out of time and money...

Sincerely,

- Sean
Attached Thumbnails
I’m Diagnosing SSL Compressor Issues - Please Advise (SSL, GSSL,etc. Rack Compressor)-continuity_test_1_both_channels_same_1-24-19.jpg   I’m Diagnosing SSL Compressor Issues - Please Advise (SSL, GSSL,etc. Rack Compressor)-left_channel_in_and_out_voltage_readings.jpg   I’m Diagnosing SSL Compressor Issues - Please Advise (SSL, GSSL,etc. Rack Compressor)-right_channel_in_and_out_voltage_readings.jpg   I’m Diagnosing SSL Compressor Issues - Please Advise (SSL, GSSL,etc. Rack Compressor)-right_sidechain_channel_voltage_readings.jpg   I’m Diagnosing SSL Compressor Issues - Please Advise (SSL, GSSL,etc. Rack Compressor)-main_board_voltage_and_ic_tests.jpg  

I’m Diagnosing SSL Compressor Issues - Please Advise (SSL, GSSL,etc. Rack Compressor)-updated_left_sidechain_ic_voltages_1-31-19.png  
Attached Files
File Type: pdf GBUS CIRCUIT DESIGN.pdf (862.3 KB, 11 views)
Old 28th January 2019
  #9
Thank you to my Friend eddie ciletti who got back to me with a possible solution in a PM prior to SSL and anyone on GS... If you have gear you really care about, I highly recommend sending it to EC .... Look him up ... Eddie Ciletti: From Digital Audio to Vacuum Tubes! ...He really is, the real deal.

- SRW
Old 28th January 2019
  #10
Lives for gear
 

I was going to think this out a bit and post some troubleshooting hints based on your last reply to me, but maybe thanks to Eddie you don't need further help at this point. Let us know how it goes.
Old 28th January 2019
  #11
Thank You David, and no disrespect intended...

He inferred from the voltage data inconsistencies that I may have arced something, while testing, which I indeed had done on an IC... He suggested I look at resistors 38 and 39, and their resistance was in fact almost gone.

I will say SSL has been nice, but this is something they totally missed? And I sent them these 4 pics this morning with resistor names?

SSL - "Our techs have been pouring over the information in drive link that you have sent us and thank you for those. They have not been able to find the answer and believe that the best course of action would be for them to have the unit in to the factory for repair."
Attached Thumbnails
I’m Diagnosing SSL Compressor Issues - Please Advise (SSL, GSSL,etc. Rack Compressor)-r38l.jpg   I’m Diagnosing SSL Compressor Issues - Please Advise (SSL, GSSL,etc. Rack Compressor)-r39l.jpg   I’m Diagnosing SSL Compressor Issues - Please Advise (SSL, GSSL,etc. Rack Compressor)-r38r.jpg   I’m Diagnosing SSL Compressor Issues - Please Advise (SSL, GSSL,etc. Rack Compressor)-r39r.jpg  
Old 29th January 2019
  #12
Lives for gear
 

If I were SSL I probably wouldn't be able to conclude anything from those photos.

(But I would have spelled "poring" correctly. Or maybe actual liquids were involved. )

If a resistor has failed it will usually look brown or burned.

If you suspect a resistor, determine the value is from its markings or the schematic, lift one leg to isolate it from the rest of the circuit, then measure it. Otherwise, other components and residual voltages will often cause erroneous readings.

Hope that helps.

Last edited by David Kulka; 29th January 2019 at 08:06 AM..
Old 29th January 2019
  #13
Hey David - Those pics above (from my last post) are labeled by resistor on the schematic, out of circuit readings for the 10 ohm resistors in question. (The resistors are actually fully out of the board in pics 3 and 4 and clearly in the picture.)

Eddie had the same info as SSL before the specific resistor readings he suggested I take...above.

SSL had the benefit of the clearly labeled DMM 10 Ohm Resistor Reading Pictures from my last post, Eddie suggested I take, and still gave the reply above...as did you.

FYI
Old 30th January 2019
  #14
Lives for gear
 

It's difficult because in the first two photos, the glare of the lamp makes it impossible to see what's being measured, and the color bands on the resistors can't be clearly seen in any of the photos. The resistor in the third photo might be burned, but it's hard to see the condition. The resistor in the fourth photo might be 10 ohms (does it have a yellow band?) but again, it's hard to be sure. If those photos were clear, it would be so much easier to give a helpful response.

This doesn't seem to be going well. I'm going to PM you with my email address. If you want to start over and give this another shot, let's continue one-on-one by email. If you give me clear info about what's going on and send clear photos, I'll try my best to help you. If something useful comes of that maybe we can share the results on this thread later on, to help others that might be dealing with similar problems.

Last edited by David Kulka; 31st January 2019 at 04:03 AM..
Old 31st January 2019
  #15
I replaced the bad resistors in question and am still getting low voltage readings on the right side.
Old 31st January 2019
  #16
Lives for gear
 
gyraf's Avatar
 

I just hope you realize just how much effort it takes to dig into and understand your way of notating the error - if it was described in a somewhat more standardized way, I'm sure it would have been much easier to help you. You probably don't realize this, but remote diagnosis is really really difficult if you don't have live-access to measurements as they are done.

I mention this because your last post could be understood as if you are complaining about free advice that deeply competent engineers are trying to give you - and I for one would find it sad if they stopped helping random strangers because of (what could be construed as) ungrateful bitchin'

With all respect,

Jakob E.
Old 31st January 2019
  #17
Lives for gear
 

I'd be grateful SSL and the others got back to you at all. Your compressor is well out of warranty and skilled electronics engineers don't come for free.
Old 31st January 2019
  #18
Quote:
Originally Posted by SeanRyder View Post
Thanks again.... You and SSL both missed even the very low Resistance reading for just the 4 resistors Eddie Cilette sugested I Test, above, he was able to diagnose just based on the voltage measurements I took... which everyone had access to...

There is no need to see and speculate what the actual resistors looked like, the readings are above... Comment 11.

Thanks for being willing to actually look at the data this time, which is more than I can say for SSL...

But tough to justify sending something off to England, or anywhere, for a team that can’t see the very low 10 ohm readings above... or even knowing where to look...

Again Eddie Was the only one to identify where to look, and everyone else missed the low readings in the four pictures of reading he sugested I look?
Am I reading this right? You got help from a friend after failing to diagnose yourself and are now throwing shade on people who tried to help you remotely? David Kulka is one of the most known and respected repair techs in Los Angeles, where there are more studios per square mile than anywhere in the world besides maybe Tokyo, and he just attempted to help you through a repair for free. I personally have received work from clients in the past just because they couldn't wait in the long cue for David's attention, but yet you are somehow unhappy with him helping you in his personal time and insinuating his repairs are not worth your money?
Old 31st January 2019
  #19
Valid points...

But more people seem to take the time to comment on a comment than the question and the data?

There are 14 comments and 0 suggestions?
Old 31st January 2019
  #20
Lives for gear
 
TobyToby's Avatar
 

Quote:
Originally Posted by SeanRyder View Post
Thanks again.... You and SSL both missed even the very low Resistance reading for just the 4 resistors Eddie Cilette sugested I Test, above, he was able to diagnose just based on the voltage measurements I took... which everyone had access to...

There is no need to see and speculate what the actual resistors looked like, the readings are above... Comment 11.

Thanks for being willing to actually look at the data this time, which is more than I can say for SSL...

But tough to justify sending something off to England, or anywhere, for a team that can’t see the very low 10 ohm readings above... or even knowing where to look...

Again Eddie Was the only one to identify where to look, and everyone else missed the low readings in the four pictures of reading he sugested I look?

Send this Fckr straight to Eddie then : ) You are unable to do a proper trouble shooting in the device and your are not able to communicate your problem and your doings properly
Old 31st January 2019
  #21
Lives for gear
 

Quote:
Originally Posted by gyraf View Post
I just hope you realize just how much effort it takes to dig into and understand your way of notating the error - if it was described in a somewhat more standardized way, I'm sure it would have been much easier to help you. You probably don't realize this, but remote diagnosis is really really difficult if you don't have live-access to measurements as they are done.

I mention this because your last post could be understood as if you are complaining about free advice that deeply competent engineers are trying to give you - and I for one would find it sad if they stopped helping random strangers because of (what could be construed as) ungrateful bitchin'

With all respect,

Jakob E.
Agreed. I felt a bit shocked and insulted, reading that reply from the OP. (I see that it has been edited now, with the nasty bits removed.)

Until reading that I was prepared to take an hour or two out of my work week to help the OP make some progress.
I don't mind dealing with resistance measurement problems, but I'm not willing to deal with resistance, and what feels like an argument, from someone that I'm trying to help at no charge.

Last edited by David Kulka; 31st January 2019 at 09:18 PM..
Old 31st January 2019
  #22
  1. Compressor Started Having Intermittent Short on Right Side that Seemed Affected By Turning Ratio (Though that moves entire switching PCB so that could be inconclusive.)
  2. Through Testing Voltages I Arced an IC and Based on Sugestion from Eddie I used a DMM to test 10 ohm Resistors R36R, R37R out of circuit (readings are labeled by resistor on schematic above)
  3. I also tested R38R, R39R, R36L, R37L
  4. R36R, R37R, and R36L Tested Very Low and Were Replaced
  5. I Continue to Have Low Voltage Readings on the ICs, ONLY on the Right Side?


This is all my tests, schematics, pics, etc... SSL FX G384 INFO – Google Drive

I removed the reply in question and have respect for David and Jakob and their knowledge... I don't know the rest of you...
This seems to have gone a little sideways, maybe thats my fault... I thought my reading were pretty clear, even typed up most of my readings, as suggested...But I'm the one looking for answers.

Sincerely,

- Sean Ryder Williams
Old 31st January 2019
  #23
Lives for gear
 
TobyToby's Avatar
 

Quote:
Originally Posted by SeanRyder View Post
  1. Compressor Started Having Intermittent Short on Right Side that Seemed Affected By Turning Ratio (Though that moves entire switching PCB so that could be inconclusive.)
  2. Through Testing Voltages I Arced an IC and Based on Sugestion from Eddie I used a DMM to test 10 ohm Resistors R36R, R37R out of circuit (readings are labeled by resistor on schematic above)
  3. I also tested R38R, R39R, R36L, R37L
  4. R36R, R37R, and R36L Tested Very Low and Were Replaced
  5. I Continue to Have Low Voltage Readings on the ICs, ONLY on the Right Side?

This is all my tests, schematics, pics, etc... SSL FX G384 INFO – Google Drive

I removed the reply in question and have respect for David and Jakob and their knowledge... I don't know the rest of you.

Sincerely,

- Sean Ryder Williams
In your schematic for the left channel your are stating a voltage reading of -2 on pin7 from the LF256N. It should read +18V. So you don't have +18VDC on this power rail at all?
Old 31st January 2019
  #24
Double Checking...

IC1L - 18v
IC2L - 18v
IC3L - 18v

"I replaced the bad resistors in question and am still getting low voltage readings on the right side."

Right Side ICs are still in the mVs

Updated Test Folder Also... SSL FX G384 INFO – Google Drive
Old 31st January 2019
  #25
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TobyToby's Avatar
 

Quote:
Originally Posted by SeanRyder View Post
Double Checking...

IC1L - 18v
IC2L - 18v
IC3L - 18v

"I replaced the bad resistors in question and am still getting low voltage readings on the right side."

Right Side ICs are still in the mVs

Updated Test Folder Also... SSL FX G384 INFO – Google Drive
First step. Remove the op-amps IC1L -IC3L and measure again at pin 7. They should be in a socket
Old 31st January 2019
  #26
Ok remove ICs where I'm getting appropriate readings? and test?

These are all positive Volts sorry if the dash was confusing...

IC1L +18v
IC2L +18v
IC3L +18v

and ICs are all currently in.
Old 31st January 2019
  #27
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TobyToby's Avatar
 

Measure for the 18VDC voltage output directly at the leg of the positive voltage regulator. It is either a LM7918 or MC7918 (fixed voltage), positive Voltage out on the right leg . . . or a LM317 (adjustable regulator) positive Voltage out on the middle leg
Old 31st January 2019
  #28
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TobyToby's Avatar
 

Quote:
Originally Posted by SeanRyder View Post
Ok remove ICs where I'm getting appropriate readings? and test?

These are all positive Volts sorry if the dash was confusing...

IC1L +18v
IC2L +18v
IC3L +18v

and ICs are all currently in.
You contradict your own info atm

Negative voltage should be on pin 4 & positive voltage on pin 7. Don't flip the probes or it will be the other way around.
Old 31st January 2019
  #29
Quote:
Originally Posted by TobyToby View Post
Measure for the 18VDC voltage output directly at the leg of the positive voltage regulator. It is either a LM7918 or MC7918 (fixed voltage), positive Voltage out on the right leg . . . or a LM317 (adjustable regulator) positive Voltage out on the middle leg
From Left to Right of VR
18+
18+
30+

Left ICs above were all measured at Pin7

Left Pin4s are measuring .8 V
Old 31st January 2019
  #30
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TobyToby's Avatar
 

Quote:
Originally Posted by SeanRyder View Post
From Left to Right

18+
18+
30+
+18VDC on pin 7 correct ?
What do you read on pin 4 ?

and where have you found +30VDC. The device has a +/-15VDC rail as well for the VCA's. You have +30VDC if measured across +/-15VDC


I see, you have measured pin 4
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