GSSL HELP THREAD!!!

[Ericbazaar]

The best thing would be to get the basic GSSL working correctly, and then take the add-ons one at a time.
Error-tracing easily gets too complex. Temporarily install the two 47K's where you've connected sidechain pcb, and take it from there.

Hi again,

ok i deinstalled the sidechain board. solder all to basic gssl mode! The same problem, sound going in, sound came out and makeup gain works, but threshold, attack and release without function. i hold the pcb under the light and look for solder bridges, nothing! test all cable connection 3 times...all ok (i think). the vca's not seem to work? how can I test the motherboard?

many thanks

Hello,

No Help? Please... :-\

Ok, i know this problem came very often to, but i can't read 300 of sides in this Threat. My English is not very good. i read many sides and some solutions were discussed. many errors are: bad soldering, bad TL074, wrong input wiring, the voltage regulators 7915, 7815, 7812 ect.
I have all checked and i find a micro solder bridge on the 56k resistor next to TL072 opamp, but it was not :-[!
The Compressor is still not working, but in my Test Something has happened. i came with my fingers back on the pins from the Ratio switch and the compressor reduce the gain...this is very strange. There is a checklist for the compressor, with the correct voltages? i have checked all resistors, 4 1k of the vca board resistors do not show the correct values (ca 760ohm) but these are 1k resistor! I do not know what to do :'(

-eric​​

again!!

I do not understand why no one answer me! someone has a tip for me? something which I can work? I would be very grateful for help.

-eric

 

[Harpo]

Eric, most resistors will measure a different value in circuit because there are other parts in series or parallel.
Check control board for shorts (FI between red and orange wire at the connection to main pcb), correct part values and parts orientation.
Do you have the sidechain board still connected (and power supplied) or have the bypass wiering done on control board instead, else the relais might be missing power to change over from bypass.
Follow and measure signal in the sidechain section, IE signal level at the HPF bridge same as input level after line receivers ? Case not, measure the (milli)voltage at sidechain-VCA pin 3 in respect to 0V reference voltage and report back.
(I once posted some ideas to fix a not working unit for a previous revision at http://www.groupdiy.com/index.php?topic=47.msg483540#msg483540. This might help you a little.
Btw. I told you that compression will not work if you didn't link external send/return on sscf pcb only if your scf selector would be set to external.

 

[submergent]

other ideas?

Leaky 22uF cap located between 78L12 out and 20K resistor ?
Tantalum caps on control pcb connected the wrong way round ?
You already double checked parts values and orientation (especially the threshold pot and parts connecting to it) ?
Distant mounting of the vreg requires cap between Vin and 0V reference voltage close at the vreg.
Using the 7815 as preregulator for the 78L12 by moving the 10R as previously described still seems the safer bet to me. YMMV.
From your previous wording 'LED i added on the 12' you seem to have more than one LED connected to the +12V rail.
Good luck.

youre the man Harpo -
i think the move of the 10R to link the output of the 15v reg to the 12 did the trick.
+12v looks nice and steady now.
dare i re-assemble and rack it??

why not.

thanks again!

-pete

whoa - hold the phone.....
my problem is back. Crazy! it's like someone snuck into the shop and un-did my mod to the 12v reg.
unit stays up for a minute or two and then out the +12 goes.

time to double check (or triple) all the stuff in and around the control board / threshold pot.

ugh.

-pete

 

[gyraf]

could be a result of ambient temperature change. Try heatsinking the 78L12?

Jakob E.

 

[Harpo]

my problem is back. Crazy! it's like someone snuck into the shop and un-did my mod to the 12v reg.
unit stays up for a minute or two and then out the +12 goes.

Oh these snuckers with too much spare time, modifying gear, misadjusting trimmers, .. Why couldn't they fix broken gear instead ..

Measure voltage drop across this 10 ohm resistor or measure voltage at input of 78L12 (resistors other end is at +15V after the mod. Seems easier than cutting a trace) to calc the current consumption of the +12V rail. What is this 10 ohm resistors power rating ?
There must be a faulty/leaky part in the sidechain section, drawing more current than usual.
When buying a not working unit, you never know wich way round polarized parts once might have been fitted.

 

[submergent]

Harpo -

yeah - looks like there's a 340mv drop across that moved 10R, as opposed to a 250mv drop across the other 10R for the -12v rail.
all the electrolytics look like they are right way round... i started replacing some of them along the +12 path.... but still same problem. i'm running low on 22uf caps... so:

i broke down and just ordered a new kit from PCB Grinder... i figured i could build a known working one faster than futzing around with this thing. thanks for the help in the meantime though. hopefully we uncovered enough here to help someone in the future with a similar problem.

-pete

 

[living sounds]

Today I replaced some xlr connectors in a GSSL with sidechain high pass filter that had been working fine before. Now it's got a problem I cannot find the cause for:

Moving the threshold knob makes the meter jump as if it were compressing, and the effect is more pronounced with fast movements. This is independent of the sidechain filter's position, and happens with only the sidechain ICs (THAT2180, TL072, TL074 and the NE5532 on the small sidechain board) connected. The voltages on the sidechain 5532 seem to be off, with it not present pins other than the psu pins show 1.3V DC max, with it connected they are all quite high up to +-14V or so.

What is really confusing me is that I hadn't touched anything that should cause such a problem... Otherwise it's working fine... Any hint on where to look would be nice, thanks!

 

[MeToo2]

Today I replaced some xlr connectors in a GSSL with sidechain high pass filter that had been working fine before. Now it's got a problem I cannot find the cause for:

Moving the threshold knob makes the meter jump as if it were compressing, and the effect is more pronounced with fast movements. This is independent of the sidechain filter's position, and happens with only the sidechain ICs (THAT2180, TL072, TL074 and the NE5532 on the small sidechain board) connected. The voltages on the sidechain 5532 seem to be off, with it not present pins other than the psu pins show 1.3V DC max, with it connected they are all quite high up to +-14V or so.

What is really confusing me is that I hadn't touched anything that should cause such a problem... Otherwise it's working fine... Any hint on where to look would be nice, thanks!

+-14V  means the op amp is saturated as near to the power rail as it can get.
Check the individual feedback loops of the op amps, correct power to each op amp. and grounding.

 

[living sounds]

+-14V  means the op amp is saturated as near to the power rail as it can get.
Check the individual feedback loops of the op amps, correct power to each op amp. and grounding.

Thanks alot! That solved it, the grounding was at fault here, as the sidechain boards ground was not connected to the main ground. 

 

[thepraqtice]

Hello GSSL thread,

Just wondering if anyone can shed any light on an issue I'm having with my GSSL build.

It's made with Turbo, 2xSSC and CRC mods so I've posted about it in a separate thread here:

http://groupdiy.com/index.php?topic=53784.0

I'm getting very aggressive distortion in right output when a signal is fed into the left input. Individually each channel sounds/compresses great but as soon as I have them together I get this incredible non-linear distortion on the right output.

Has anyone encountered anything like this in their builds so far?

If I had a malfunctioning opamp or vca could this sort of thing happen? I swapped the VCA's but the distortion problem still resides on the right output from a signal at the left input.

I took out all the opamps and measured voltages and they all seem to be ok.

I have also snipped Pin 4 on my That 2180B VCA's but haven't removed any of the resistors/trimmers in the vca section, is this likely to cause a problem like this?

All connections between boards seem to be good and apart from the distortion everything on the unit seems to work as it should.

Here's a link to how I have the boards wired incase anyone can see any issues with my wiring that might be the cause of this:

https://dl.dropboxusercontent.com/u/4364451/GSSLTURBOSSCCRCLAYOUT.jpg

Any help or advice very much welcome.

Many thanks,

Sam

 

[Harpo]

I'm getting very aggressive distortion in right output when a signal is fed into the left input. Individually each channel sounds/compresses great but as soon as I have them together I get this incredible non-linear distortion on the right output.

In GSSL mode or turbo mode and both SSCF boards switches to bypass ?
Sure the pole of the turbo/gssl toggle connects to the top of the 15K (double value for balanced out operation) input resistor through the -from your wiring overview- light blue wire ? (connecting it to the top of the right side removed 47K resistor, just next to the top of the left side removed 47K resistor that feeds the upper SSCF board through the violet wire would be less confusing with a pic showing a previous revision board from year 2002).
You'd need a Y cable with two T/S plugs for your external SCF XLR socket, just saying.
The not shown turbo board ratio connections go to free pole and throw connections at the ratio lorlin switch on control pcb ?
The VCAs pin5 is a current source that connects to the -15V rail through a 5K1 resistor for the audio VCAs and to the -12V rail through 3K9 resistor(s) for the sidechain VCA(s).
I'd get the gssl running first and add turbo and SSCF boards later on. Your fault could be in either of these boards.

 

[frazzman]

Hey guys, I am apologising in advance here for reinventing the wheel with this question....
I've been over the threads and followed recommendations in other posts.

Anyhow, I have a build on my bench that has the dreaded level issue between channels. Left looks to be around 6db lower than right.

As previous posts have suggested, I've checked voltages on my working (right) side and compared to the left.

Measuring in DC, the voltages of each channel are near identical on all opamps and VCAs. Having completed the rudimentary stuff like checking for shorts, replacing ICs, checking molex & XLR wiring etc, what would the next step be?

If I recall there use to be a schematic floating around that had the expected voltages (unless I have confused that with the 1176 one?)

With the DC voltages checking out I am at a bit of a loss here... thanks in advance

 

[MeToo2]

Hey guys, I am apologising in advance here for reinventing the wheel with this question....
I've been over the threads and followed recommendations in other posts.

Anyhow, I have a build on my bench that has the dreaded level issue between channels. Left looks to be around 6db lower than right.

As previous posts have suggested, I've checked voltages on my working (right) side and compared to the left.

Measuring in DC, the voltages of each channel are near identical on all opamps and VCAs. Having completed the rudimentary stuff like checking for shorts, replacing ICs, checking molex & XLR wiring etc, what would the next step be?

If I recall there use to be a schematic floating around that had the expected voltages (unless I have confused that with the 1176 one?)

With the DC voltages checking out I am at a bit of a loss here... thanks in advance

Feed a low frequency mono AC tone into both channels. Not really critical what it is, but 50Hz is a good start if you are measuring with an AC multimeter. Step through the circuits until you find a point where the left channel is quieter/ reading lower AC than the right. A 6dB difference should stick out like a dogs nuts = 1/2 the voltage. It's almost certainly one half of the the last de-belancer is either not being fed with an input signal, or is not outputting anything, or you are shorting the out of phase output to ground.

 

[ArnoldLayne]

Hi all,

I built a kit from Gustav with rev 11 PCB and THAT 2180B's, and I'm having two issues with it:
1. Same problem as Frazzman, except on the right side.
2. When I lower the threshold, both channels start distorting more and more. I think the controls are working, but it's hard to tell because of the distortion, and I don't have a meter yet.
I checked the position of all diodes and caps, and continuity and shorts at the connections between the PCBs. I tried switching the VCA's and the opamps around with no change, checked the opamp voltages, as well as on the VCA sockets. I get 0V on pins 5 and 7 of the sidechain VCA socket. Shouldn't I get +/-12V ?
Also, I noticed that 7915 gets very hot, and 7815 even hotter. Voltages are +15V & +22V for 7815, and -15 & -22V for 7915.

Does anyone have an idea ?

 

[frazzman]

Hi all,

I built a kit from Gustav with rev 11 PCB and THAT 2180B's, and I'm having two issues with it:
1. Same problem as Frazzman, except on the right side.
2. When I lower the threshold, both channels start distorting more and more. I think the controls are working, but it's hard to tell because of the distortion, and I don't have a meter yet.
I checked the position of all diodes and caps, and continuity and shorts at the connections between the PCBs. I tried switching the VCA's and the opamps around with no change, checked the opamp voltages, as well as on the VCA sockets. I get 0V on pins 5 and 7 of the sidechain VCA socket. Shouldn't I get +/-12V ?
Also, I noticed that 7915 gets very hot, and 7815 even hotter. Voltages are +15V & +22V for 7815, and -15 & -22V for 7915.

Does anyone have an idea ?

Hi Arnold, you definately have a short around the 78L15 and 79L15 regulators... 22V is way too high.... the regulators should not be near that hot. Once you have resolved that issue the distortion should go, your voltages at the ICs will be off too as a result... you won't be getting the 12V you're expecting on the VCAs with this issue present

 

[frazzman]

Hey guys, I am apologising in advance here for reinventing the wheel with this question....
I've been over the threads and followed recommendations in other posts.

Anyhow, I have a build on my bench that has the dreaded level issue between channels. Left looks to be around 6db lower than right.

As previous posts have suggested, I've checked voltages on my working (right) side and compared to the left.

Measuring in DC, the voltages of each channel are near identical on all opamps and VCAs. Having completed the rudimentary stuff like checking for shorts, replacing ICs, checking molex & XLR wiring etc, what would the next step be?

If I recall there use to be a schematic floating around that had the expected voltages (unless I have confused that with the 1176 one?)

With the DC voltages checking out I am at a bit of a loss here... thanks in advance

Feed a low frequency mono AC tone into both channels. Not really critical what it is, but 50Hz is a good start if you are measuring with an AC multimeter. Step through the circuits until you find a point where the left channel is quieter/ reading lower AC than the right. A 6dB difference should stick out like a dogs nuts = 1/2 the voltage. It's almost certainly one half of the the last de-belancer is either not being fed with an input signal, or is not outputting anything, or you are shorting the out of phase output to ground.

Hi MeToo2, thanks for putting me on the right track. If I interpret what you're saying correctly, along with the schematic...

At the input opamps section I should see the same AC reading on Pin 6 of each 5534 opamp, correct?

This certainly is not the case. For example on the left 5534 - pin 6, I have 0.260vac, where as on the right 5534 I have 1.8VAC, these values increase/decrease exponentially as the signal level is increased....

Am I on the right track? If I am, any pointers on where to look? I have checked component designations and orientations and I can't seem to find any evidence of any shorts.

Thanks again

 

[ArnoldLayne]

Hi Arnold, you definately have a short around the 78L15 and L9L15 regulators... 22V is way too high.... the regulators should not be near that hot. Once you have resolved that issue the distortion should go, your voltages at the ICs will be off too as a result

Thanks Frazzman,
do you mean around the 7815 and 7915 regulators ? Actually, the 23V is coming straight off the bridge rectifier, but I have 18V at the secondaries. Isn't the rectifier supposed to give out the absolute value in DC ?
I'm still a noob in electronics so I'm a bit confused  :-[

 

[MeToo2]

Hey guys, I am apologising in advance here for reinventing the wheel with this question....
I've been over the threads and followed recommendations in other posts.

Anyhow, I have a build on my bench that has the dreaded level issue between channels. Left looks to be around 6db lower than right.

As previous posts have suggested, I've checked voltages on my working (right) side and compared to the left.

Measuring in DC, the voltages of each channel are near identical on all opamps and VCAs. Having completed the rudimentary stuff like checking for shorts, replacing ICs, checking molex & XLR wiring etc, what would the next step be?

If I recall there use to be a schematic floating around that had the expected voltages (unless I have confused that with the 1176 one?)

With the DC voltages checking out I am at a bit of a loss here... thanks in advance

Feed a low frequency mono AC tone into both channels. Not really critical what it is, but 50Hz is a good start if you are measuring with an AC multimeter. Step through the circuits until you find a point where the left channel is quieter/ reading lower AC than the right. A 6dB difference should stick out like a dogs nuts = 1/2 the voltage. It's almost certainly one half of the the last de-belancer is either not being fed with an input signal, or is not outputting anything, or you are shorting the out of phase output to ground.

Hi MeToo2, thanks for putting me on the right track. If I interpret what you're saying correctly, along with the schematic...

At the input opamps section I should see the same AC reading on Pin 6 of each 5534 opamp, correct?

This certainly is not the case. For example on the left 5534 - pin 6, I have 0.260vac, where as on the right 5534 I have 1.8VAC, these values increase/decrease exponentially as the signal level is increased....

Am I on the right track? If I am, any pointers on where to look? I have checked component designations and orientations and I can't seem to find any evidence of any shorts.

Thanks again

Absolutely. Pin 6 of 5534. Pin 1 5532. Pin 7 5532. s/c in (47K) from L & R = "to sidechain".
Should all measure pretty much identical when comparing the same point on the L&R channels, when in mono operation.

You seem to have a clear problem either on your input wiring, or on the input de-balancer (5534). And it's way more than 6dB.

Look to the left of that point on the schematic.

Start with measuring pins 2 and 3 of your XLR. Then junction 22k+22uF. Then pin 6.

Could be a dry joint. Duff cap. Duff op amp. Something pretty basic in any case.
You could also try swapping over the 5534 op amps left/right if they're socketed to see if the problem moves with the op amp or stays with the channel.

From what I remember there's not a lot of physical space around those components.

 

[ArnoldLayne]

OK, I solved my lower right signal problem: it was an unbalanced XLR/Jack adapter  ...

But I still don't understand why my 7815 and 7915 regulators are heating up so much..
They have respectively +/-22.7V at the input and +/-14.9V at the output .
7815 is heating up the most.

 

[Harpo]

But I still don't understand why my 7815 and 7915 regulators are heating up so much..
They have respectively +/-22.7V at the input and +/-14.9V at the output .
7815 is heating up the most.

Whatever magnitude 'so much' might be ... heatsinks have been invented for this reason.
The differential between vregs input and output in V times connected load in A is the generated heat in W. A single incandescent lamp (FI illumination for GR-meter, illuminated switches, ...) might draw more current than the complete GSSL and up to now only you know what and how you have connected any additional parts. For usual the vregs in the GSSL, when built as shown on schematic, do not require additional heatsinking with a 2*15VAC or 30VAC center tapped mains transformer in front.