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Old 4th March 2005, 10:54 AM   #1
S.C is offline S.C  United States
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Thumbs down Blow up once, Blow up twice and Blow up somemore

I blowed Caps, blowned diodes, and broke the copper on PCB. Finally, I blow up the LM3875.....

I finally got my 25V+25V PS fix.... it actrually come out to be 38.3-.7 +/-

Before I put the PS back together, I was using a stable 12V supply to run the amp section, No Problem.

Later I fixed the 25V+25V PS and connected to the Amp section, and the chip blow as soon as I turn on the power.

After the Chip blow, the PS still fine and getting the same reading.

Then I wonder can I connect PG+/- together from the amp section then out to a cable to the rectifer board? Because it is connect together in amp section anyway.

*********PG+ ---*****************-----PG-*************
Amp section******\ One Power cable /********Rectifer board
***************/-----------------\*******************
*********PG- ---*****************-----PG+*************

* = empty spaces

The problem is my amp section.... 3:45am... I need to sleep now. Continue tomorrow. Pictures tomorrow too.
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Old 4th March 2005, 06:04 PM   #2
revell is offline revell  Belgium
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I blew some LM's too: in my case it was caused by switching V+ and V-.
As for the grounding issue: I would say keep PG+ and PG- separate. It was designed this way probably for a reason
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Old 4th March 2005, 08:31 PM   #3
jleaman is offline jleaman  Belgium
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Pictures of the blown parts of pictures of the wiring setup ? both would help us help you..


J'
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Old 4th March 2005, 11:18 PM   #4
S.C is offline S.C  United States
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Left Channel Blown Chip
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Left Channel Full View
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Right Channel Blown Chip
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Right Channel Full View
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THE PROBLEM
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The wire on the paper suppose to be V- but I put V+ there.....

I have a question. How come I use the a electric meter to test the connectitive. The meter beep when I connect everthing together while I put the niddle to V+ and V-? If I test The Power Supply allone, the meter won't beep. Is it the blown chip bridge or it is suppose to be like that? Also should I replace ever compounet or I just change the chip?
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Old 4th March 2005, 11:50 PM   #5
hifi is offline hifi  Sweden
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Tip of the day : If the wires carries different signals/voltages use different coluors!
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Old 4th March 2005, 11:54 PM   #6
jleaman is offline jleaman  Belgium
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I cant really tell but it looks like that resister is in the wrong spot and looks to be shorting stuff out. got a better Picture. ?
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Old 5th March 2005, 02:17 AM   #7
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Quote:
Originally posted by jleaman
I cant really tell but it looks like that resister is in the wrong spot and looks to be shorting stuff out. got a better Picture. ?

Yeah it looks as if it might be a cold solder as well?

Nice pictures though.
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Old 5th March 2005, 03:25 AM   #8
S.C is offline S.C  United States
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OK ! It is offical that I only mixed up V+ and V-. Now I changed the chip and switch the V+/V- back to normal. Now sounds is coming out. Thx guys !
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Old 5th March 2005, 07:57 AM   #9
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The meter beeps because capacitors are shorts for a while. If you leave the meter there long enough for the capacitor to charge up, the beeping would stop.
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Old 5th March 2005, 04:04 PM   #10
speaker is offline speaker  United States
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Default Old curmudgeon carpenter sez.......

"Measure thrice, cut once!"

Having let the smoke out more than once over the years myself, I finally started triple-checking before I turned on the juice. Nothing like having a PS capacitor pop right in your face though. Smells like victory!



speaker
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