GSSL HELP THREAD!!!

[wthrelfall]

Well, tonight was "The Big Switch On" - needless to say it didn't quite go according to plan...  It took only a few seconds to start smoking  so we killed the power.  On inspection, 2 of the 10r resistors on the Expat CRC board have burnt out.  Anybody know what might be the problem?  I presume the wiring from the transformer to the CRC board is the same as going straight to the GSSL motherboard, ie. centre tap (orange & red) to centre hole, black and yellow to the adjacent holes (with the polarity being unimportant due to AC)?
My first instinct was to suspect the rectifier on the CRC board..  if it was faulty would it take out these resistors?
thanks in advance for your help!

PS. I remember once seeing a post in this thread with a diagram showing the Voltage test points - I've been searching for it all day but can't find it   can anyone point me in it's direction?
cheers.

 

[Chrome Heart]

After a year and a half one of my GSSL's stopped compressing. No trauma, no visible sign of component damage. The bypass still works because it disables the makeup gain and the unit still passes audio. No distortion or other symptoms, just no compression. Any suggestions where to look? This is a basic construction, no sidechain, HPF, etc.
...bummer

 

[Chrome Heart]

Well, tonight was "The Big Switch On" - needless to say it didn't quite go according to plan...  It took only a few seconds to start smoking  so we killed the power.  On inspection, 2 of the 10r resistors on the Expat CRC board have burnt out.  Anybody know what might be the problem?  I presume the wiring from the transformer to the CRC board is the same as going straight to the GSSL motherboard, ie. centre tap (orange & red) to centre hole, black and yellow to the adjacent holes (with the polarity being unimportant due to AC)?
My first instinct was to suspect the rectifier on the CRC board..  if it was faulty would it take out these resistors?
thanks in advance for your help!

PS. I remember once seeing a post in this thread with a diagram showing the Voltage test points - I've been searching for it all day but can't find it   can anyone point me in it's direction?
cheers.

Sounds like a solder bridge or a component installed in the wrong direction.

 

[Harpo]

After a year and a half one of my GSSL's stopped compressing. No trauma, no visible sign of component damage. The bypass still works because it disables the makeup gain and the unit still passes audio. No distortion or other symptoms, just no compression. Any suggestions where to look? This is a basic construction, no sidechain, HPF, etc.
...bummer

+/-12V rails alife? Oxydated lorlin-type switch?

 

[Chrome Heart]

After a year and a half one of my GSSL's stopped compressing. No trauma, no visible sign of component damage. The bypass still works because it disables the makeup gain and the unit still passes audio. No distortion or other symptoms, just no compression. Any suggestions where to look? This is a basic construction, no sidechain, HPF, etc.
...bummer

+/-12V rails alife? Oxydated lorlin-type switch?

Thanks Harpo. Yes voltages at the rails are correct. I did suspect that maybe the ratio switch might be the culprit but I havent tested that yet. I hope to get to it today

 

[Chrome Heart]

Okay so I checked all the voltage points according to the attached doc. and replaced all the IC's (I have a bunch of extras) and aslo switched out all the Lorlins. I checked the control PCB for shorts and still no compression. It is possible for a VCA to just "die"?

 

[wthrelfall]

I disconnected the CRC board and wired the toroid straight onto the motherboard, switched it on for about a minute (no smoke), turned off, then checked the board for anything suspicious - nothing found, except a mildly hot toroid..  Is it normal that it gets warm so quickly?  what's the 'normal' running temp of a torroid?

EDIT: Just noticed the rectifier is burnt out 
don't really understand what's going on, checked for shorts and there's none..

Well, tonight was "The Big Switch On" - needless to say it didn't quite go according to plan...  It took only a few seconds to start smoking  so we killed the power.  On inspection, 2 of the 10r resistors on the Expat CRC board have burnt out.  Anybody know what might be the problem?  I presume the wiring from the transformer to the CRC board is the same as going straight to the GSSL motherboard, ie. centre tap (orange & red) to centre hole, black and yellow to the adjacent holes (with the polarity being unimportant due to AC)?
My first instinct was to suspect the rectifier on the CRC board..  if it was faulty would it take out these resistors?
thanks in advance for your help!

PS. I remember once seeing a post in this thread with a diagram showing the Voltage test points - I've been searching for it all day but can't find it   can anyone point me in it's direction?
cheers.

Sounds like a solder bridge or a component installed in the wrong direction.

 

[wthrelfall]

Anyone there that can help?  I'm stumped.  Checked and checked for shorts, nothing found.  Is my transformer putting out too much power/voltage? 
thanks.

I disconnected the CRC board and wired the toroid straight onto the motherboard, switched it on for about a minute (no smoke), turned off, then checked the board for anything suspicious - nothing found, except a mildly hot toroid..  Is it normal that it gets warm so quickly?  what's the 'normal' running temp of a torroid?

EDIT: Just noticed the rectifier is burnt out 
don't really understand what's going on, checked for shorts and there's none..

Well, tonight was "The Big Switch On" - needless to say it didn't quite go according to plan...  It took only a few seconds to start smoking  so we killed the power.  On inspection, 2 of the 10r resistors on the Expat CRC board have burnt out.  Anybody know what might be the problem?  I presume the wiring from the transformer to the CRC board is the same as going straight to the GSSL motherboard, ie. centre tap (orange & red) to centre hole, black and yellow to the adjacent holes (with the polarity being unimportant due to AC)?
My first instinct was to suspect the rectifier on the CRC board..  if it was faulty would it take out these resistors?
thanks in advance for your help!

PS. I remember once seeing a post in this thread with a diagram showing the Voltage test points - I've been searching for it all day but can't find it   can anyone point me in it's direction?
cheers.

Sounds like a solder bridge or a component installed in the wrong direction.

 

[Harpo]

Anyone there that can help?  I'm stumped.  Checked and checked for shorts, nothing found.  Is my transformer putting out too much power/voltage?

Only connect the CRC pcb for now. A blown bridge rectifier needs replacement. For your bridge rectifier, use the highest current rating avail. that fits your pcb and comes with the correct shape and pinout of ~+~- or whatever permutation needed. When connecting this polarized part, make sure both rectifiers '~' AC connections go to the transformer side, the '+' to the positive and the '-' to the negative DC side of your CRC board. You already confirmed, the electrolytic caps are on pcb in correct orientation (case not, they will be blown and kill the rectifier again). Power up and measure the raw +/- DC voltages with respect to your transformers center tap or the 0V connection of your CRC board. Nothing else connected, the DC voltage reading will be about +/-22V with your 2*15VAC transformer in front. All fine? reconnect your GSSL to the CRC board.
Good luck

 

[wthrelfall]

Thanks Harpo, will try that later.
Before I got your reply I replaced the bridge rectifier and turned it on again, with the same result - rectifier burning out.  it's a 400V rectifier, I'm orienting the positive with the + on the board.  All caps and diodes are also correctly oriented.  Transformer wired as per your instruction earlier.
Might the electrolytic caps be blown from the first switch on, hence now burning the rectifier every time?

Anyone there that can help?  I'm stumped.  Checked and checked for shorts, nothing found.  Is my transformer putting out too much power/voltage?

Only connect the CRC pcb for now. A blown bridge rectifier needs replacement. For your bridge rectifier, use the highest current rating avail. that fits your pcb and comes with the correct shape and pinout of ~+~- or whatever permutation needed. When connecting this polarized part, make sure both rectifiers '~' AC connections go to the transformer side, the '+' to the positive and the '-' to the negative DC side of your CRC board. You already confirmed, the electrolytic caps are on pcb in correct orientation (case not, they will be blown and kill the rectifier again). Power up and measure the raw +/- DC voltages with respect to your transformers center tap or the 0V connection of your CRC board. Nothing else connected, the DC voltage reading will be about +/-22V with your 2*15VAC transformer in front. All fine? reconnect your GSSL to the CRC board.
Good luck

 

[Harpo]

rectifier burning out.  it's a 400V rectifier,

What's its current rating ? (This question relates to your transformers VA rating, so a higher VA rated transformer will need a rectifier with a higher current rating to stand the inrush current).

I'm orienting the positive with the + on the board

So this single leg is correctly orientated. The remaining 3 legs of your rectifier match as well ? (Bridge rectifiers come in any thinkable permutation of ~+~-, ~+-~ or +~~-, circular shaped ones might be different from square or rectangular shaped ones, ...)

Might the electrolytic caps be blown from the first switch on, hence now burning the rectifier every time?

For usual a diode will blow faster than a cap, but you need a little luck that this diode(s) inside the bridge rectifier blow open circuit, not short circuit when they let the smoke out.

 

[MeToo2]

Thanks Harpo, will try that later.
Before I got your reply I replaced the bridge rectifier and turned it on again, with the same result - rectifier burning out.  it's a 400V rectifier, I'm orienting the positive with the + on the board.  All caps and diodes are also correctly oriented.  Transformer wired as per your instruction earlier.
Might the electrolytic caps be blown from the first switch on, hence now burning the rectifier every time?

Got to be a short circuit or misaligned component. If necessary remove the caps for now and just check the rectification. Have you checked the polarity of the rectifier with a multimeter capable of diode testing? Remember a standard ohmmeter may not put out enough voltage in resistance mode to make a diode conduct (hence the diode test mode) http://www.youtube.com/watch?v=dqkT6hF0O3E

 

[wthrelfall]

Hi Harpo.  Thanks for responding. 
the rectifier connections match the connections on the circuit board and is rated at 1.5A 400V, http://docs-europe.electrocomponents.com/webdocs/0927/0900766b80927a05.pdf
My transformer is 30VA 2x115v: http://cpc.farnell.com/jsp/search/productdetail.jsp?SKU=FF01543

rectifier burning out.  it's a 400V rectifier,

What's its current rating ? (This question relates to your transformers VA rating, so a higher VA rated transformer will need a rectifier with a higher current rating to stand the inrush current).

I'm orienting the positive with the + on the board

So this single leg is correctly orientated. The remaining 3 legs of your rectifier match as well ? (Bridge rectifiers come in any thinkable permutation of ~+~-, ~+-~ or +~~-, circular shaped ones might be different from square or rectangular shaped ones, ...)

Might the electrolytic caps be blown from the first switch on, hence now burning the rectifier every time?

For usual a diode will blow faster than a cap, but you need a little luck that this diode(s) inside the bridge rectifier blow open circuit, not short circuit when they let the smoke out.

 

[wthrelfall]

:'(

Hi Harpo.  Thanks for responding. 
the rectifier connections match the connections on the circuit board and is rated at 1.5A 400V, http://docs-europe.electrocomponents.com/webdocs/0927/0900766b80927a05.pdf
My transformer is 30VA 2x115v: http://cpc.farnell.com/jsp/search/productdetail.jsp?SKU=FF01543

rectifier burning out.  it's a 400V rectifier,

What's its current rating ? (This question relates to your transformers VA rating, so a higher VA rated transformer will need a rectifier with a higher current rating to stand the inrush current).

I'm orienting the positive with the + on the board

So this single leg is correctly orientated. The remaining 3 legs of your rectifier match as well ? (Bridge rectifiers come in any thinkable permutation of ~+~-, ~+-~ or +~~-, circular shaped ones might be different from square or rectangular shaped ones, ...)

Might the electrolytic caps be blown from the first switch on, hence now burning the rectifier every time?

For usual a diode will blow faster than a cap, but you need a little luck that this diode(s) inside the bridge rectifier blow open circuit, not short circuit when they let the smoke out.

 

[Harpo]

Rectifier rating seems OK. Transformer secondaries always have been connected to CRC input with the transformers center tap connected to the center pin of your input connection ? Nothing else connected to CRC board, there will be a short on PCB or a failed cap draws more current than your rectifier can stand. A magnifying glas might help you or a close up pic might help us to spot it.

 

[wthrelfall]

some photos (burnt out bridge rectifier removed).  CRC board shows 2x burnt resistors from 1st switch on awaiting replacement. Note: the first time I switched on, the transformer cables were soldered directly to the board (not molex), could possibly have shorted out at this stage damaging a component on the motherboard, hence the rectifier burning out now? 

Rectifier rating seems OK. Transformer secondaries always have been connected to CRC input with the transformers center tap connected to the center pin of your input connection ? Nothing else connected to CRC board, there will be a short on PCB or a failed cap draws more current than your rectifier can stand. A magnifying glas might help you or a close up pic might help us to spot it.

 

[Harpo]

some photos (burnt out bridge rectifier removed).  CRC board shows 2x burnt resistors from 1st switch on awaiting replacement. Note: the first time I switched on, the transformer cables were soldered directly to the board (not molex), could possibly have shorted out at this stage damaging a component on the motherboard, hence the rectifier burning out now?

At CRC input? No. This would have shorted out a transformer winding. At CRC output this might have caused this fault.
Assuming 'burnt out bridge rectifier removed' is both rectifiers at CRC and GSSL or did you link the AC inputs to the correct +/- rectifier terminals on GSSL board from traceside?
You have connected the center pin of CRC-out to the center pin of GSSL AC-in by the RED wire?

 

[wthrelfall]

some photos (burnt out bridge rectifier removed).  CRC board shows 2x burnt resistors from 1st switch on awaiting replacement. Note: the first time I switched on, the transformer cables were soldered directly to the board (not molex), could possibly have shorted out at this stage damaging a component on the motherboard, hence the rectifier burning out now?

At CRC input? No. This would have shorted out a transformer winding. At CRC output this might have caused this fault.
Assuming 'burnt out bridge rectifier removed' is both rectifiers at CRC and GSSL or did you link the AC inputs to the correct +/- rectifier terminals on GSSL board from traceside?
You have connected the center pin of CRC-out to the center pin of GSSL AC-in by the RED wire?

Sorry I'm getting confused.  I want to re-cap:

1st switch on:

Transformers output connected to CRC input - (centre tap (orange & red) to centre hole on CRC.  Black and Yellow to adjacent holes, order not specified from Expat.)
CRC output to GSSL - (CRC centre hole to GSSL centre hole.  Adjacent holes connected as per Expat audio photo (there was no instruction on which holes on the CRC to connect GSSL so I looked at their wiring and copied it))
All power connections soldered directly to the PCB's (through from the top, soldered on the bottom).

Result = Smoke rising, 2x burnt out 10 Ohm resistors on CRC board.  Killed power immediately (10 seconds from switch on).  No other visible damage.  (Bridge rectifier on CRC board looks ok, rated at 106v 1.5A - Quoted from Expat CRC manual: "1x Bridge Rectifier ~ usually 50V and 1.5A should be enough.")

2nd switch on:

CRC board taken out of the chain - transformer output direct to GSSL board.  Molex connector now on transformer cables to GSSL board.  Orange & Red to centre hole.  Black and Yellow to adjacent holes.

Result = after 30 seconds smoke rises, power killed.  Bridge rectifier (400V 1.5A, correctly oriented) burns out.

3rd switch on:

Bridge rectifier is replaced with identical component.  Wiring is the same.

Result = @ 30 seconds there is smoke, power killed, another blown rectifier.

I have not yet connected the CRC board alone as per your suggestion.  I will endeavour to do this when I have time.

Hope this helps!

 

[Harpo]

Looks like a  short between 7815 pins 1/2 that is the most likely cause of your failing parts.

 

[wthrelfall]

Looks like a  short between 7815 pins 1/2 that is the most likely cause of your failing parts.

Hmm, I don't think so - it's just flaked flux...  but i'll re-try :-\