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Old 4th December 2004, 08:42 AM   #21
Nuuk is offline Nuuk  United Kingdom
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Did you re-measure the DC offset on the faulty channel?

Try to build your amp onto a piece of wood first. I can't recommend this method strongly enough as it makes fault finding much easier. Once it is working 100%, then is the time to build it into a fancy/compact case.
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Old 5th December 2004, 12:47 AM   #22
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Yep, it still is at -35VDC.

I whole heartedly support your idea of building the amp outside the box. I just wish I'd done that ;-)

Still waiting to hear from Brian Bell.

Thanks,
Bret Morrow
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Old 8th December 2004, 07:50 AM   #23
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Just wanted to let you know that theese chips do come faulty every once in a while.

my lm4700 (30W) amp had one faulty chip. i measure a almost direct short (2.9ohms) between the -rail and output witch results in you-know-what: -22V at the output. I'l have to send it back again, nothing i did wrong, i know: I sat for 4 hours on end trying to locate the mistake I'v made, but no shots anywhere, exept internally in the chip.

the chip altso got warm as hell when connected. if yours do to, then i suspect you'v got the same problem.

regards
marius
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Old 8th December 2004, 03:10 PM   #24
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Quote:
Originally posted by demogorgon
Just wanted to let you know that theese chips do come faulty every once in a while.

my lm4700 (30W) amp had one faulty chip. i measure a almost direct short (2.9ohms) between the -rail and output witch results in you-know-what: -22V at the output. I'l have to send it back again, nothing i did wrong, i know: I sat for 4 hours on end trying to locate the mistake I'v made, but no shots anywhere, exept internally in the chip.

the chip altso got warm as hell when connected. if yours do to, then i suspect you'v got the same problem.

regards
marius
Thanks, I appreciate hearing this. A faulty chip is the only thing that I think it can be now. I've traced & retraced all the wires & tested everything I could think of looking for something--anything. The only indication of anything wrong is the output & input ends of the chip: -35VDC offset at the speakers & the 10VDC offset at the input.

Still waiting to hear from BrianGT--I think he must be away this week.

Cheers,
Bret Morrow
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Old 8th December 2004, 03:21 PM   #25
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Default Correction!

Quote:
Originally posted by JazzzSpazzz


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Still waiting to hear from BrianGT--I think he must be away this week.
Correction, BrianGT contacted me.
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