Re: Need some help with an Atari Switching Power Supply

Q1, Q2, U5, and U7 all connect to the same heat sink.
Could in a previous repair attempt someone did not use
the mica insulators between the heat sink and amps
or the plastic insulators on the screws ?

On a power supply of this age I would remove and measure the
capacitance of voltage doubling caps C6 and C7.

Also you said with pin 10 of U1 disconnected, several caps
exploded on the -31.5 volt line. This makes BR4 (16amp 150V Diodes)
suspicious. Using a scope check the waveform 5.
Does it look like the picture for 5 or 6 ?

Tim

>On Wed, 09 Jul 2008 15:06:49 -0700, Matt Rossiter
>wrote
>
>This is just a little update. When I removed L6 the +5v came up just fine
>and the regulator didn't shut down.
>http://games.rossiters.com/manuals/IR-PS2-1.jpg
>So the problem is definitely in the audio section of the board. I'm still
>trying to find where the problem is. I've replaced the audio amps and some
>of the capacitors. I can't find any bad resistors. There seems to be loose
>a ground somewhere because if I touch something metal like the coin door
>frame or the power switch I can feel a slight tingle of electricity. Not a
>huge shock, but enough to be a little uncomfortable. I'm wondering if that
>might have something to do with it.
>
>The boards seem to work fine with the ribbon connectors I made. It's
>reporting a bad ram, but I'm not going to keep powering the boards up until
>I resolve this loose ground issue.
>
>Matt
>
>
>
>
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Received on Thu Jul 17 15:06:24 2008