Weird PPA problem
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hypophysis

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I have a very weird problem with my PPA.
It has a V1.0 PCB and Glassmans diamond buffers, power supply is a Mascot 2083 linear regulated.
Since some weeks the amp sometimes doesn't power up when switched to on. When I try some time later it works fine again. It never fails when it's already on.
Today I had the same problem again, and I searched for loose contacts, but couldn't find one. I tried to measure voltage between V+ and V- of the buffers and in the moment I touched the buffer's pins with the multimeter's tips, the amp powered up and worked fine again.
Is this problem caused by high rail capacitance on the amp and missing protection diodes in the power supply? I sometimes read about problems with this constellation, but didn't really understand what problems can occur.
If so, can this cause any harm to my ppa or to the power supply?
 
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dviswa

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Have you considered replacing the sockets the buffers are on? Somehow I get a feeling this is a dry solder or loose/bad contact situation. Or maybe just reheat the solder points with some flux so that dry joints maybe eliminated.
 
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hypophysis

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Quote:

Originally Posted by dviswa
Have you considered replacing the sockets the buffers are on? Somehow I get a feeling this is a dry solder or loose/bad contact situation. Or maybe just reheat the solder points with some flux so that dry joints maybe eliminated.


But I don't think a loose contact on the buffers can prevent the whole amp from powering up. Soldering on the amp is perfect, it's been done by doobooloo.
 
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@sia@home

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how big is your rail?

Mine is 5440uF, but I haven't powered it on yet, due to still missing some vital parts.
 
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tangent

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It's possible that the power supply is having a hard time during the turn-on time. Often a regulator will stay near 0V (2-3V at most, not enough to turn the LED on, or allow it to be bright if it is on a little bit) if it's having a hard time getting started. Too much rail capacitance is one way this can happen.

Also possible is that the buffers or the op-amps are licked up at one rail for some reason, and touching the meter probes to the rails "unlocked" them.

When you get it into this condition again, measure from V+ to V- again, at the DC input jack. If the amp doesn't come up, the value here might be educational. If this always brings the amp up, let us know that, too. It might help us understand what's going wrong.

And no, the lack of a power supply diode will not cause this problem.
 
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