my gssl smoked on first power up!

[gerardmanvuca]

hey guys, on powering up my 1st gssl the 10R resistor, on the negative 12V rail, smoked! i figured out why its because i wired the yellow and black wire on my toroid to the board the wrong way round. i figured out how to do it correctly from sintecs image....check it HERE.

i then wired it correctly and there was no smoke but none of the knobs work and there is no compression. the board does pass audio but i think i might of fried some of the sidchain. my readings are good for 15v+/- but i cant get a -12v reading. i can get a +12but only in one location.......

i'm a rookie so if u guys have any ideas wats wrong with my gssl please let me know.......cheers guys

 

[CurtZHP]

Perhaps your -12V regulator got cooked. I'd start there.

 

[Greg]

Definitely focus on the power supply. Ohm out the -12V rail. Is it shorted?

 

[gerardmanvuca]

thanks for the help guyz......umm i got no idea how to ohm out the rail.....i figured out how to measure the volts and resistance and using the beep thing to check connections but thats as far as i got. i'm at a bit of a loss as to wat pins to check, pos?neg? where do i start from, the reg maybe?

 

[Greg]

"Ohm out rail" simply mean a -12V poin on the PCB. With unit OFF, measure the resistance there referenced to ground. I "ohm out" every rail before powering up any piece of gear.

 

[gerardmanvuca]

ok i replaced the 12v regulators, the tl072, tl074 and its still not compressing or doing anything when i turn the knobs. i noticed that when i took out the tl072 the audio got much louder. any ideas wat that could mean? all the VCAs are workin. the led on the control panel works but none of the knobs..........can anyone advise me on wat to try next....thanx

 

[Rob Flinn]

[quote author="gerardmanvuca"]....can anyone advise me on wat to try next....thanx[/quote]

Look for shorts on the board & check your soldering carefully

 

[gerardmanvuca]

i have been checkin them and they are all shiny, no blobs, 100% no shorts......somthing is weird here..........uggh.....this suks.....i'm at a loss.....maybe i should just pull the sidechain and start it again..

 

[Rob Flinn]

[quote author="gerardmanvuca"]i have been checkin them and they are all shiny, no blobs, 100% no shorts......somthing is weird here..........uggh.....this suks.....i'm at a loss.....maybe i should just pull the sidechain and start it again..[/quote]

It sounds perhaps like you may have a problem from the switch board to the mother board. Does your make up gain control work. If you use a meter from ground to the wiper it should change V as you adjust it. This is also true for the threshold. If that works then trace it to the motherboard to see if the voltage changes there. Also check that you have the bypass switch hooked up correctly.

Other than that there is a massive thread on how to fault find the GSSL, if you use the search function. It may pay you to look at it, that way you will get to learn fault finding, which is very useful !!

 

[gerardmanvuca]

hey thanx for the help......i did wat u advised and yes i am gettin voltage changes with both pots on the control board...i can trace the threshold to the motherboard to pin 2 on the tl072 and i get a voltage change......but when checking the make up gain at pin 5 or 6 i get no reading changes.........so the control panel is defin working but yet theres no compression or change in sound when i turn them??

and i do make searches and i found people with similar problems but their solutions havent worked for me.......i think it safe to say that the problem is round the tl072/4 chips but i have no idea wat..

my make up, thresh, atack release and ratio work but arnt affecting the sound in anyway?????? sorry to be a pain but please help if anyone has anymore solutions.....thanx again

 

[gerardmanvuca]

PLEASE SOMEONE HELP!....ahhhhh....gettin so frustrated.........ok i've figured out that i've got bad 12vdc readings........my 15vdc+/- readings are perfect but on the 12v rails i get a reading of 3.4V.......this must be the problem then.......
-i've replaced all caps, resistors(10r), 12v regulators in the power supply and i'm still getting the same readings........b4 u ask I HAVE NO SHORTS OR BAD SOLDERING!....i scanned the pcb and checked in detail and the solders are all good.

-my contrl panel works because i get volt changes when i turn the knobs....just no change to the sound........

-the audio is losing about 12-14 db in volume after the tl072.....i know this because when i pull that chip out the sound goes to full volume.

if i'm getting this low reading (3.4vdc) on the 12v rails why could this be????
PLEASE SOMBODY, ANYBODY! thanx

 

[Guest]

Why the shouting?
Place this in the SSL help thread as that is where this sort of thing goes
You have traced the 12 v until it goes bad?
You are frustrated after only a week of debugging...

 

[gerardmanvuca]

sorry i dont mean to accross as angry.....i just am a bit gutted.i was extremly carefull building the ssl and measured all resistors and took extra care to put everything in the right place and yet it still doesnt work.the only thing i messed up on was attaching the power supply wrong on first power up...

i did put this in the ssl help thread but after a couple of days without replies i moved it to the lab and i got replies within a couple of hours.

i'm just at a complete loss and am looking for suggestions on why i have low voltages on the 12v rails and wat i can do. sorry if i sound angry i'm just frustrated as all attempts to fix so far have failed......i'm also a newbie learning as i go which doesnt help....but i'm getting there.

 

[Guest]

So where does the 12V go bad ???

 

[gerardmanvuca]

oh yeah sorry........looking at the schematic i see the 12v starts after the 12 v regs.....but they are measuring 3.4 straight off the pins

 

[gyraf]

Measure voltages at the appropiate pins on the IC's.

Measure with reference to 0V/Gnd on the pcb.

Jakob E.

 

[gerardmanvuca]

Here are the readings I get on the appropriate pins on the IC's

- tl074

in 6 = -1.29
in 5 = 0
in 3 = 0
in 13 = -2.1
in 12 = 0

tl072

in 3 = 0
in 8 = -3.22

Thanks a lot for the help guyz, much appreciated.

:thumb:

 

[Guest]

Gerard
Go back to the 12v regulator
put one probe on 0V and the other on the 12V line just after the regulator - what does it measure?
What does it measure just before the regulator?

 

[gerardmanvuca]

Here are the measurements for;

- 12V right after the regulator = 3.3

- just before the regulator = I'm not sure where to measure to get the measurement before the reg, is it after the + 22cap?. The other pins I've tried around that area are not giving me any readings.

thanks,

 

[Greg]

I think it's clear that something is dragging down the 12V rails.