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Old 11th February 2008, 05:30 PM   #1
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Default Pearl channel short-circuited

Hi,

I think I have blown my left channel with my power cord (linking the power supply to the Pearl). I may have inverted ground and V+ or earth grounded one of the pin while the other having the supply. I can now only hear a low hum in the output.

It appear that I have a short-circuit because the transformer is overheating and the voltage between the ground and the V+ of the Pearl board is 0. When I test the impedance between these two pins, I also get 0. This is obviously not the case for the other working channel.

I have removed C1, C2, C3 & Q1 and still get a 0 ohm between Ground and V+. Should I continue removing parts and test for short-circuit or there are other alternative? Any other part could cause this? I don't have a scope unfortunately...

Thanks
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Old 11th February 2008, 06:10 PM   #2
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Shoot.... I know how you feel, having had DIY circuits DOA.

If I were you I'd replace all actives and electrolytic caps.
The alternative is that you understand the circuit enough to
troubleshoot it and you have also a sig gen and scope.

Sorry, that's probably not what you wanted to hear.

The good news is Pearl is a great design and not at all finicky so
if you can get it rebuilt you should be fine.
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Old 13th February 2008, 05:45 PM   #3
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found the problem, it was the damn 5-pin XLR cable I bought on ebay. The pin-3 of the XLR connector was electrically connected to the connector itself. I was powering the pin-3 that was short-circuited to the ground. Next time I will make my own cable or use a DB25 like Pass Labs
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Old 13th February 2008, 05:55 PM   #4
Manu is offline Manu  Europe
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BTW :Nice projects on your homepage.
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