Voltage Reg(7905) Exploded Off Midway 90411

cwstrong

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I've been having some power issues with my Wizard of Wor, so I rebuilt the Midway power supply (90411) using the Bob Roberts rebuild kit. Finished the overhaul, plugged it in and got a load buzz coming from the speakers...then POP! and there goes the new 7905 voltage reg. Actually blew the top of the transistor off!

Nothing else burned on the board, not even the fuse, so what the hell could be causing what I'm guessing is a voltage overload?

Thanks!
 
i would say replace the 7905, reinstall or preferably replace the diodes, and try it at that point and see what happens.
 
Hopefully the only other casualty is the capacitor between the diodes and the voltage regulator. The regulator should've stopped the voltage going out.
 
Yeah, the only other inline component is the 2200uf cap. I'll replace the (2) diodes and 7905 and cross my fingers. Nothing like a dumb mistake when soldering at 11:00pm at night.

Thanks for the help guys!
 
Yeah, the only other inline component is the 2200uf cap. I'll replace the (2) diodes and 7905 and cross my fingers. Nothing like a dumb mistake when soldering at 11:00pm at night.

Thanks for the help guys!


Dont feel bad, I was banging out a bunch of repairs the other night on little sleep and installed a cap backwards on a monitor chassis. I noticed the cap quickly but it took me a while to track down the resistor that burned up because of it.
 
Today I replaced the (2) backwards diodes and the 7905 and everything is back to 100% again!

Moral of the story....double and even triple check your work after 9PM at night! :)

Thanks again!
 
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