Power Supply Meltdown

jgeiger

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The Peter Chou switching power supply in one of my games started smoking the other day. Opening it up there are two resistors that are scorched black. Looks like they are labeled D12D13 on the board. I picked up a replacement from Bob Roberts but was wondering if I should be concerned about hooking the new one up to the same machine. I measured the AC and the voltage seems to be correct coming out of the connector for the power supply. Anyone have any idea on whether or not this might just fry another PS or would it have been power supply specific?

Also, this is for a Dragons Lair 2 cabinet.

Thanks for any help.
 

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Those are diodes :)

I would chalk this one up to a simple power supply failure. Even if something in the game was shorting out, it should put the power supply into shutdown, not burn it up. Unless of course, it was something on the -12 rail or somesuch - those aren't always protected. Hard to say what circuit that's in from the picture. But, I seriously doubt that it's the games fault - especially if it was working before.

-Ian
 
Looks to me (see attached diagram) like D12 & D13 are the -5V rectifiers.

IC3 is just a 7905 (common -5V regulator). Not sure what kind of internal protection those have, but something was pulling a lot of current to burn those diodes. Perhaps the regulator itself shorted? C26 short?
 

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