my gssl smoked on first power up!

[gerardmanvuca]

ok i'm starting to be a bit less of a rookie dumbass.....i figured out how to take readings so here are ome of them in a pic..... i dont think they're to good......any thoughts? also i've just realized that i bought a 1.5amp bridge rectifier instead of the stated 1amp in the gyraf list......could this be the problem?

here is the pic:

 

[Guest]

Gerard
AFAIK The 1.5amp rectifier shouldn't be a prob
Can you zoom in on and post a piccie of the board around the 12v rectifier - you sure you havent any solder bridges or cut traces there - dont forget to check the other side?

 

[gerardmanvuca]

here it is......its as close as i could get.i'm pretty sure as i can be that there are no shorts or traces..... cheers

 

[Guest]

Is the regulator in the right way round? - sorry for daft question

 

[gerardmanvuca]

he he...thats ok i appreciate the help.......yeah definitly in right way round as according to pcb marking and gyrafs scheme....it just seems that some of the voltge readings i'm getting are way, way off.....how cud they be so far off.....weird

 

[Greg]

Check soldering (with ohmmeter) and resistor values around the TL074 and TL072.

Also disconnect daughter board and see if anything changes.

 

[gerardmanvuca]

ok will check today.........but isn't thr problem with the power supply if the 12v rails are so off the mark?? or do componants in the sidechain affect the voltages of the 12v rails??

 

[waldorfcave]

Have you really check the orientation of the 12v recitfier?Some time ago i got nearly the same problem. Check the datasheet of the rectifier.

 

[fucanay]

What power transformer are you using that you are getting almost 24 volts to the regulators. I wonder if you may be blowing those. Do you have the datasheet for the regulators and transformer you used. Either way, I'll bet all of the regulators are getting pretty hot with that high input voltage since you are turning half of the input voltage into heat. Remember it's supposed to be a 15-0-15 or 18-0-18 power transformer in the GSSL, though I think most people use the 15-0-15.

Matt

 

[gerardmanvuca]

here is the power tran i'm using...it's 15/15

here is how i've wired it to the board.....on first power up i had wired the yellow and black wires the wrong way round....this is when the 10R resistor on the -12vdc rail smoked....after i switched the wires and replaced the resistor i didnt get any smoke.......i also replaced all caps and 12v regs (in the 12v power supply)since then but the board still registered the same voltages and nothing changed

bridge rectifier is alligned with positive pin with the hole marked with the "+" sign.

all regulators have the same specs as stated on the gyraf bom.and they all seem to be at an ok level of heat(i can touch them comfortably without getting burnt)..apart from the 78L12 regulator which gets VERY HOT!(to hot to touch for more than a second).

yeah i thought the 23V thing is very weird...if the tran is 15/15....how the hell am i getting 23??????????strange.....i must be missing somthing but everything i check seems to be in order

 

[waldorfcave]

Maybe change the 12 v rectrifier to bigger ones. in every of my 4 ssl i used
"to 220" 1 amp 12v rectrifier.

 

[fucanay]

Looking at the datasheet posted on RS (search for 0015P1-2-015) , it appears that the Black and Orange wires go in the middle positions and the yellow and red go to the outsides. That would explain the high voltages and possibly the blown 12 volt regs. Give it a look.

Matt

 

[gerardmanvuca]

aha.....sounds promising.... i will swap them....does it matter which way they go? or can i just swap the yellow and orange leads?........much thanx for the help dudes....i would be screwed without this cool ass forum u guyz rule

 

[gerardmanvuca]

ok so i swapped the orange and yellow wires round...but the readings are still exactly the same and still no compression.........dunno wat to try next :?:

 

[dinesh]

Hi

Its better you disconnects the toroidal & check the secondary with AC volt meter. Then connect it again & check DC voltage at pin 1 & pin 3 of voltage regulators.

 

[gerardmanvuca]

hi, i disconected the toroid and tested with ac voltmeter and got a reading of roughly 18v for both secondaries......upon reconecting i got the same readings as earlier round the pins on the reg......on the 15v regs i get 15vdc on one pin and 23vdc on the other same for both pos and neg regs.........at the 12v regs i get 23vdc at pin 1 and 3.3vdc at pin 2



dunno if this means anything but i tried just coneccting one of the secondary supplys and left the other one out.........the measuments i took on the volt meter were just exactly the same as when both supplies were connected..........dunno if that means anything .................i should maybe point out than i'm not taking readings from any of the ic pins.....only because i'm thinking that if the power is wrong this is what i should be concentrating on......get that working then then start thinking about ICs..........is this a wise choice?.........

i think i'm gunna go to maplins and get a new bridge rectifier

 

[Harpo]

[quote author="gerardmanvuca"].........at the 12v regs i get 23vdc at pin 1 and 3.3vdc at pin 2[/quote]
don't think so. 78L12 and 79L12 have different pinout.
78L12 is Pin 1,2,3-Input,Ground,Output.
79L12 is Pin 1,2,3-Ground,Input,Output.
You may have the wrong part for the -12V regulator. The labeling is sometimes hard to read.
For your transformer the 23Vdc is the expected value after rectification (Vac - diode loss * 1.414) feeding the regulators.

 

[gerardmanvuca]

i've been tryin to get my newbie brain around this one but surely if theres 15v coming in....how is that being changed into 23v???i mean isnt that against the laws of science (unless u beleive in coldfusion)......or am i just being stupid.....of course thers 220v going in the toroid but as far as my measurments go i'm getting a maximum of 18 v out the secondaries....(which doesnt seem right anyay if its a 15/15)..........oooofff i'm very confused right now.....maybe i should just buy a new power tran(maybe onboard or sumthin)...............as far as i can tell, when i trace the 23vdc back it starts at the bridge rectifier......but they dont increase the voltage do they....just switches ac to dc (according to wikipedia) :?: :?: :shock:

 

[gerardmanvuca]

[quote author="Harpo"]
don't think so. 78L12 and 79L12 have different pinout.
78L12 is Pin 1,2,3-Input,Ground,Output.
79L12 is Pin 1,2,3-Ground,Input,Output.
You may have the wrong part for the -12V regulator. The labeling is sometimes hard to read.
For your transformer the 23Vdc is the expected value after rectification (Vac - diode loss * 1.414) feeding the regulators.[/quote]

yeah....no i meant pin 1 (input) pin2 (output)........but u r of course totaly correct pin3 is output......i do have the right regs as i read 0v at the middle pin on the 78 and ov at the first pin(1) on the 79........my bad...

oh so there is meant to be 23v at the rectifier......aha......so is it after the 12v regs that its supposed to come down to 12v?........

 

[matta]

Hi Gerardmanvuca,

Can you post a pic of the component side of the board? It may help us help you track down an error that you MAY have missed.

Cheers

Matt