GSSL HELP THREAD!!!

[MikeClev]

If you have other GSSLs would you be able to hook up the main pcb to a different front panel PCB? and connect the troublesome front panel to a different main pcb? That would at least tell you which board the problem was on.

Also... just thought of this... double check that the wire jumper is fitted on the control pcb next to the meter wire and above the wires going to the main board... without that compression is bypassed

 

[Siegfried Meier]

Is it possible that a short on the main board could cause the threshold to not work?

I've scoured and searched, and have not found anyone else to have had this problem.

Help please, this thing's got me mad stumped!!

Sig

 

[Harpo]

Is it possible that a short on the main board could cause the threshold to not work?

Yes, and some other possibilities, IE broken pcb trace, broken opamp or 2M2 or whatever instead of 220k input resistor to summing node to TL072-pin2.
Measure voltage at threshold wiper. Should read -12V in full CW position and about 0V (+0.3V with 47k at the ccw pot end) when dialed in full CCW.
More likely you only might have reversed the pot outer wires or the 47k series resistor connected to the wrong side of the threshold pot.
Good luck.

 

[Siegfried Meier]

Definitely no broken trace, or opamp as I've swapped them with a known working unit.

Will check resistors again and voltage thanks!

 

[Siegfried Meier]

I'm getting -24.6V on full CW, and 0V on full CCW...what does this mean?

However, I should point out that I get the same reading on a fully working unit...

Thanks!
Sig

 

[Siegfried Meier]

I also don't use the 47K resistor on the pot, never have, never felt the need to.

Anyone else have any advice?  This is absolutely ridiculous.  I've never spent this much time troubleshooting...

Thanks,
Sig

 

[Harpo]

I'm getting -24.6V on full CW, and 0V on full CCW...what does this mean?

Meaning, you either have your black probe for reference voltage connected to +12V instead of 0V, or you reversed the +12V/0V wires between main pcb and control pcb.
Threshold wiper voltage should be varying in range -12V/+12V with 0V in center position for your build without the 47k at the CCW end.

 

[Siegfried Meier]

Yes, with respect to ground, I get 12.2v, so that seems to be correct.

I've gone over the wiring to the PCB from the control board a hundred times, every wire is accurate, has conduction, and is wired up correctly.

The problem has to be somewhere else.  The pot also shows it's 50k resistance when measured, so the pot can't be bad, can it?  I'm reaching here...

 

[Siegfried Meier]

AAAARRRRRggggghhhh!!!  The classic 100k in a 100r location!!!

Oh I feel so silly...I went over and over and over with all the resistors in the sidechain, measuring them again and again.  I have no idea how I didn't come across it...

Damn me and my colour blind eyes!

Thanks for all the help!!

 

[MikeClev]

That'll do it...  I did the same with a 220r where it should be 220k coming from the threshold pot, gave me weird jumpy exaggerated threshold action. I now double check and measure every resistor I insert! As they say in carpentry- "Measure twice, cut once".

 

[Chrome Heart]

AAAARRRRRggggghhhh!!!  The classic 100k in a 100r location!!!

Oh I feel so silly...I went over and over and over with all the resistors in the sidechain, measuring them again and again.  I have no idea how I didn't come across it...

Damn me and my colour blind eyes!

Thanks for all the help!!

Ive done several of these builds and I have to say, one thing Ive taken to doing is putting all the resistors on the dmm before stuffing them in the pcb's. It takes more time to assemble but you save time troubleshooting stuff like this. 2 cents

 

[Siegfried Meier]

I measure every single resistor with the DMM as well - I also match them to be identical if there are several being used.  This eliminates any left/right level errors.  However, no amount of measuring with a DMM is going to help you if you think a spot needs a 100k, and you measure out a 100k...

 

[Chrome Heart]

I measure every single resistor with the DMM as well - I also match them to be identical if there are several being used.  This eliminates any left/right level errors.  However, no amount of measuring with a DMM is going to help you if you think a spot needs a 100k, and you measure out a 100k...

true dat

 

[Siegfried Meier]

Quick queston...

This GSSL I just finished, it works great with my bantam patchbays and AVID 192's.  However, it was hooked up to a 003 as a hardware insert and it seems that there's some kind of impedance thing happening, as no level will get into or out of it.

What are they doing in the 003?  They call it "impedance balanced", but is this the same as electronically balanced?  The unit is at a clients, and he patched a DI in between, says it works correctly.  Any clue what's wrong and how to fix it?

 

[MeToo2]

Quick queston...

This GSSL I just finished, it works great with my bantam patchbays and AVID 192's.  However, I hooked it up to a 003 as a hardware insert and it seems that there's some kind of impedance thing happening, as no level will get into or out of it.

What are they doing in the 003?  They call it "impedance balanced", but is this the same as electronically balanced?  If I patch a DI in between, it works correctly.  Any clue what's wrong and how to fix it?

I admit I don't know the details of a 003 insert so I could well be wrong here. Sounds more to me like a basic cable or routing issue. If there was an issue with balancing I'd either expect a horrible earth hum loop, or 6dB of loss (due to the -ve phase portion being tied to ground or chassis) at either mismatch point. Have you checked which combination of TRS is in use on the 003 for send and return on the insert? And also the nominal levels? Normally send would be on the tip, and return on the ring, with sleeve as ground: but not always. You can obviously check that with a simple multimeter on AC Volts after passing a tone through the path if you don't have access to a scope.

 

[ptron]

if i removed this 10K resistor from main GSSL pcb sidechain vca

4. remove the 10k resistor between VCA pins 5 and 3 (you can also remove this resistor for the sidechain VCA, see image above).  (QUOTE from calibration)

my question.. do i have to remove R17 from turbo to get it working properly? (i thought it was originally but maybe it isnt.)

i got a few questions in a previous post with no answers maybe already answered in previous post but in 120 pages of gssl thread i havent seen anything about tl072 performance regarding release RC loops... anyways.. i really wanna know if i have to chop that 10k res off my turbo!!

thanks a lot!

 

[Harpo]

if i removed this 10K resistor from main GSSL pcb sidechain vca

4. remove the 10k resistor between VCA pins 5 and 3 (you can also remove this resistor for the sidechain VCA, see image above).  (QUOTE from calibration)

my question.. do i have to remove R17 from turbo to get it working properly? (i thought it was originally but maybe it isnt.)

i got a few questions in a previous post with no answers maybe already answered in previous post but in 120 pages of gssl thread i havent seen anything about tl072 performance regarding release RC loops... anyways.. i really wanna know if i have to chop that 10k res off my turbo!!

quote from Gary Hebert 'The 10k resistor between pins 3 and 5 is really unneccesary.  It was an attempt to minimze control voltage feedthrough in the 2159 that wasn't very effective.  It's totally unnecessary for the 218x devices.'

For the 10k on turbo pcb, you should have it identical to the sidechain VCA on main pcb so both L/R behave the same. I'd leave this resistor on turbo board out as well.

 

[ptron]

will make sure it is that one (R17) before i take out the wrong one.. hehe got to see the traces carefuly

thanks a lot! getting into the second unit finally and figuring out some dodgy stuff ive done!!!

 

[beatnik]

a question about the meter.

would be ok a DC meter 0-150 mA?

the gssl specifies for 1mA, but there is a way to adapt another meter, like this one?

thanks in advance

 

[ptron]

for 100uA meter (1/10th of 1mA) u can get resistor between the 2 legs of the meter but not sure if u can do the opposite.