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Old 7th November 2012, 11:51 PM   #681
Reality first!
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Quote:
Originally Posted by Marra View Post
I will remove the diodes and see what happens.What voltage reading should I be getting across there?
I don't know, I measure voltage mainly on PS lines.

I would first fix the PS rails (+-14V).
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Old 8th November 2012, 01:44 PM   #682
Marra is offline Marra  United Kingdom
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Good news in one respect that the module that I kept refering to as the good one does actually work.I'm listening as I type
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Old 8th November 2012, 02:36 PM   #683
bcmbob is offline bcmbob  United States
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Very encouraging. Hang in there.

Dario, can you identify any practical measurement points between the two red arrows in this pic? Don't know if there may be too much interaction between components to be useful.
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Old 8th November 2012, 03:37 PM   #684
AndrewT is online now AndrewT  Scotland
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Yes.
Measure Vdrops across the passives.
Measure V across the semis (actives).
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Old 8th November 2012, 03:45 PM   #685
bcmbob is offline bcmbob  United States
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Andrew, is the PGND pad sufficient for all negative probe placement for the measurements?
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Old 8th November 2012, 03:54 PM   #686
AndrewT is online now AndrewT  Scotland
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I would use that for checking relative voltages.
But I find device Vdrops to be far more useful in trying understand a circuit and trying to debug a broken circuit. I am useless at debugging.
I found the same when running my racing cars. Because they almost always ran perfectly well, I never got a chance to develop debugging skills. People would see how well my cars ran, they would come to me with their problems, but I didn't have a clue on how they begin to debug. Ask a Garage trained Technician who looks at broken cars/circuits all day and every day. That is his forte. He does not get requests "check why my car never breaks down" !!!
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Old 8th November 2012, 04:05 PM   #687
bcmbob is offline bcmbob  United States
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Thanks, I'm sure Dario will give some direction here.

P.S. In my minds eye I'm having trouble seeing you in or around a race car. Just demonstrates how faulty our perceptive abilities can be - particularly with just online communications. The big question - were you any good.
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Old 8th November 2012, 05:43 PM   #688
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Quote:
Originally Posted by bcmbob View Post
Badri, Unfortunately it appears you will have to take the same path as Marra. The voltages are the clearest method to solving problems. The schematic is linked a few posts back, and if you have difficulties knowing where to place the probes - please post and someone will help.
Thanks Bob. I didnt do any measurement so far. I will be doing it little later because of work. But today I have checked it again. Audio coming from one channel without any hum. And I measured the DC of this. It is showing in -ve (-6). Is it normal? Or am I doing wrong? And in another board both R3 resistor and LM3886 getting too hot. Not able to touch it. The DC is 55mV. Any inputs Bob? Forgot to mention, a muffled, distorted audio is coming from the faulty board but its breaking for each second.

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Badri
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Old 8th November 2012, 06:19 PM   #689
bcmbob is offline bcmbob  United States
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It's my understanding that ~12 - 15 mv and lower is acceptable - lower is better. I noticed you replaced R3 previously so my guess would be a problem before that resistor. I hate to ask, but some pictures of the underside are needed. It's a pain to remove the module from the heat sink but those pictures are really needed to confirm a correct build.
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Old 8th November 2012, 06:24 PM   #690
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Quote:
Originally Posted by bcmbob View Post
It's my understanding that ~12 - 15 mv and lower is acceptable - lower is better. I noticed you replaced R3 previously so my guess would be a problem before that resistor. I hate to ask, but some pictures of the underside are needed. It's a pain to remove the module from the heat sink but those pictures are really needed to confirm a correct build.
Thanks Bob. I didnt replace R3 before. But I changed R11 because it got opened. Pictures of the back side of the board will be posting later because of work.

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Badri
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