Troubleshooting +5V on Midway 90400 Power Supply

Mojodog333

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Hi,

I've been working on a resurrecting a Sea Wolf in another thread, but this is specific to a common power supply so, thought I'd start a post on it. It was working fine, all voltages rock solid where they should be, then I started seeing something weird that made me want to check the power supplies. 12V and -5V are good, but the +5V (2N3055) has this ripple on it.

5V Ripple.png

I looked at the base and saw the same shape waveform, so I pulled out the schematic.

1746377693577.png

Since the 2N205 was driving the base of the 2N3055, I went to look at what was driving it, the LM305A.

Pin2 of the LM305A that is driving the 2N2905 looks like this...

Pin2 of LM305.png

At this point, my troubleshooting skills are stalled out until I read up on the LM305A, so I thought I'd throw this out there and see if this is a path anyone has gone down before.

Thanks,

-John
 

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Never mind, problem solved. The 470 µF cap on the output was bad.
 
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