GSSL HELP THREAD!!!

[daane]

Cheers! I just finished putting my together everything on my rev#11 PCB from pcbgrinder. My 10r resistor starts to smoke when i startup, except i put out the THAT2181c's. Gerardmanvuca had a thread in 2007 where he said his smoking 10r resistor was caused by wiring the black and yellow cables on the pcb board wrong. Can somebody tell me weather i did it right or weather there could be something else wrong? I had some short runs before, with some of the opamps sitting the wrong way - maybe this destroyed my THAT21801c and this causes the smoke? Im in Europe by the way, so i wired the toroidal transformer so that the red and the orange are connected.

Schematics & pictures attached. Would be awesome if somebody could help me!

 

[Script]

Impossible to say. You need to read what's written on the transformer and wire accordingly.

Yours came as a kit? If so there should be a "build butler" telling you how to wire it correctly.

Picture 2.
!!! That looks VERY dangerous !!! One single wire strand sticking out and you have a short. One solder joint comes lose and you have a short. Better use (screw) terminal block here or comparable solution.

 

[daane]

Hey thanks for your reply! It didnt came as a kit, but i used the same tranformer as in pcbrinders assembly guide.

Thanks for the tip - i'll try to get one!

 

[Harpo]

As Script already said. Hookup of transformer secondary side for this triad type transformer (colours are not standarized between different manufacturers) looks ok. Are the VCA's placed with correct orientation ? (sidechain VCA is opposite direction of audio VCA's and all IC's won't survive once powered when fitted reversed). Not power supply related, but both 47k summing resistors are missing and the jumper for HPF is missing as well. What's up with the different colour 100pF cap right side next to the TL072?

 

[daane]

The VCA´s are placed with the right orientation, im not 100% sure weather that was the case while the first startup. I thought i was supposed to put the 47k resistors out for soldering the Supersidechain wires on the backside (see attaced image). I didn't knew about that jumper i can fix that right away! The different color of the 100pF cap is because i had to buy some missing parts later on in a local shop. Is there anything i can learn from the fact that the smoke is only appearing when i put in the vca's?

 

[cluelessbloke]

Hi guys, I can't tell if im being stupid or not but i simply cant find the place on the board for the voltage regulator "79L12" as it is shown. I have found the other 3 on the board but cannot find that one, any help would be appreciated.
photo of my particular board for reference

 

[gyraf]

..ca. 5cm south of the TL074 pin4?

(the "L" series come in TO92 housing/pinout)

 

[cluelessbloke]

..ca. 5cm south of the TL074 pin4?

(the "L" series come in TO92 housing/pinout)

I really have no excuse to not finish this now, I have been labouring and researching for close to 6 hours today trying to get components in a mouser basket. Thank you so much for your help I cannot believe how I didn't see that. I was looking for another one of the same shaped markings for the other 3 on the board and couldnt see one!

thanks again

 

[atticus1872]

Hey all I apologize in advance but Ive spent days/weeks maybe even up to a month now on this help thread looking for someone who has or has had a similar issue to mine but I haven't really found anything (unless I missed something of course) so I feel compelled to ask. I recently finished building the GSSl from a partial kit (missing case, knobs, meter and transformer which is a Triad VPT36-690) Everything powers on from what I can tell and the meter works but one of the issues I'm having is while the compressor does pass audio its cutting the signal way way down. I understand thats what a compressor does but no matter where I have it set its just reducing the signal a major amount and the make up gain has no effect and the threshold knob almost acts as if its working in reverse. when the knob is turned all the way counter clockwise the meter is buried at 20db and with it all the way clockwise its sitting at zero (with the attack on slow and the release on fast) If I put the attack on fast and the release on auto it changes to about 2db) Ive never see anything like this before and I have no idea where to even begin after checking the obvious. Any advice anyone could offer would be much appreciated thank you for your time in advance!

 

[Script]

Ive spent days/weeks maybe even

Obviously, we can't have that

I take it you are describing weird compression behaviour, not weird meter behaviour ?

What meter ? You sure it works correctly ?

the threshold knob almost acts as if its working in reverse

Why almost ? CCW lowers the threshold on mine too. Provided you use a linear pot, you could change that to CW by flipping wires. But why? THR is indeed a bit sensitive depending on ratio -- at least over here.

the make up gain has no effect

That doesn't sound right. Did you check DC on all gain pot pins and all the way back to main board ?

 

[Gustav]

Sending the make-up gain CV into the side chain due to a miswired bypass switch, perhaps?

I would start by rechecking the bypass switch, then go looking at the side chain - your ratio behaviour is not suspicious in and by itself, so you have something comining into your SC, and the make-up not working would point towards a bypass switch being wirec incorrectly. One side of the bypass cuts signal just before the attack/release circuit in the side chain, and the other makes and breaks the make-up gain.

Gustav

 

[atticus1872]

Obviously, we can't have that

I take it you are describing weird compression behaviour, not weird meter behaviour ?

What meter ? You sure it works correctly ?


Why almost ? CCW lowers the threshold on mine too. Provided you use a linear pot, you could change that to CW by flipping wires. But why? THR is indeed a bit sensitive depending on ratio -- at least over here.


That doesn't sound right. Did you check DC on all gain pot pins and all the way back to main board ?

Obviously, we can't have that

I take it you are describing weird compression behaviour, not weird meter behaviour ?

What meter ? You sure it works correctly ?


Why almost ? CCW lowers the threshold on mine too. Provided you use a linear pot, you could change that to CW by flipping wires. But why? THR is indeed a bit sensitive depending on ratio -- at least over here.


That doesn't sound right. Did you check DC on all gain pot pins and all the way back to main board ?

Thank you for your help I appreciate it greatly! Yes I believe the meter is working correctly but I don’t have any solid proof other than just visually watching it (which doesn’t mean much I know) It’s a S-500 meter from Don audio. I can send audio through it and it moves in time with the signal source from what I can tell, but the unit isn’t passing audio well barely at all. It is totally possible that the meter isn’t working correctly. Forgive my ignorance but what are you referring to with CCW? I did check them but I didn’t really have a good frame of reference, what should they read? I’ll double check them later today once I’m off of work.

 

[Script]

CW = clockwise
CCW = counter-clockwise
Referring to knob rotation.

You checked CV (control voltage), which is DC (direct current), in the SC (side chain) ?

 

[atticus1872]

Sending the make-up gain CV into the side chain due to a miswired bypass switch, perhaps?

I would start by rechecking the bypass switch, then go looking at the side chain - your ratio behaviour is not suspicious in and by itself, so you have something comining into your SC, and the make-up not working would point towards a bypass switch being wirec incorrectly. One side of the bypass cuts signal just before the attack/release circuit in the side chain, and the other makes and breaks the make-up gain.

Gustav

I’ll double check that and make sure it’s wired correctly. I didn’t use a rotary switch for this just a 6 pin toggle so it’s entirely possible I made a mistake here as I found a few different ways to wire it from various sources. But I’ll check both of those it would make perfect sense now that I look at the layout. I’ll report back and let you know my findings. Thank you for your help it’s greatly appreciated!

CW = clockwise
CCW = counter-clockwise
Referring to knob rotation.

You checked CV (control voltage), which is DC (direct current), in the SC (side chain) ?

My apologies (face palm) Don’t know how I missed that. I did but i don’t remember what they were odd the top of my head. I will double check that and let you know the readings once I do!

 

[atticus1872]

CW = clockwise
CCW = counter-clockwise
Referring to knob rotation.

You checked CV (control voltage), which is DC (direct current), in the SC (side chain) ?

So I checked the control voltage but I don’t believe I’m checking in the right area so my readings were 0v or very close to it. Just to make sure my readings aren’t skewed where do I check this exactly?

 

[atticus1872]

Sending the make-up gain CV into the side chain due to a miswired bypass switch, perhaps?

I would start by rechecking the bypass switch, then go looking at the side chain - your ratio behaviour is not suspicious in and by itself, so you have something comining into your SC, and the make-up not working would point towards a bypass switch being wirec incorrectly. One side of the bypass cuts signal just before the attack/release circuit in the side chain, and the other makes and breaks the make-up gain.

Gustav

I checked the wiring to the bypass switch as far as I can tell it is wired correctly. But the build guide I have isn't great and im trying to find some material to verify that it is wired correctly.

 

[Script]

Measure between Gain pot wiper and ground.

The wiper should read between 0 and 12VDC when turned. Reads OK?

Then measure between ground and the 620k resistor (lead/leg that's facing board edge). It should read between 0 an 12VDC there too when turning the Gain pot.

If it doesn't, check the wirings of your bypass switch (where it says 'E'), just as Gustav said. Also check the other breakpoint of that switch for connectivity (btw 'C' and Attack).

 

[atticus1872]

Measure between Gain pot wiper and ground.

The wiper should read between 0 and 12VDC when turned. Reads OK?

Then measure between ground and the 620k resistor (lead/leg that's facing board edge). It should read between 0 an 12VDC there too when turning the Gain pot.

If it doesn't, check the wirings of your bypass switch (where it says 'E'), just as Gustav said. Also check the other breakpoint of that switch for connectivity (btw 'C' and Attack).

Again excuse the ignorance as I'm
New to this but is this going off of the star ground (case) or another ground and which one specifically?

 

[Script]

Just ground -- 0V.
And since in a properly built GSSL, signal ground connects to chassis ground...

 

[atticus1872]

Just ground -- 0V.
And since in a properly built GSSL, signal ground connects to chassis ground...
View attachment 98116

Thats what I had thought but didn't want to assume anything but in that case I've got next to nothing between the gain pot wiper and ground it varies between .007-.068V when rotating the pot but its erratic and doesn't follow the sweep of the pot. Same thing when going from 620K to ground but it'll get to .1V which still isn't correct. This is how I have the bypass switch wired.