I blew it - literally

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From: pintoguy <bmarchon_at_email.domain.hidden>
Date: Sat, 20 Sep 2014 10:38:03 -0700 (PDT)

So, I had a perfectly good Lisa 2/10 which I had fixed earlier (I had a short in the widget fan). Then, as I was demo-ing it to a friend, I made the mistake and opened the back cover while it was turned on. As expected, the safety switch tripped. The problem is that, since then, the Lisa won't power up. I checked that the 5V standby is there, and I also checked that I get the 18V and 170V DC in the power supply. When the PS is connected in the unloaded state, I noticed that resistors R2 and R33 and hot, but this might be normal,, as the schematics tell us that they will be dissipating about 0.5 W at idle (170V in 51kohms dissipates 170x170/51,000=0.5W). However, resistors R4, R5, R7 and R8 are also very hot to the touch. They are, from what the schematics say, part of the push-pull switching regulator.

Would anyone be able to help me ?

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Received on 2014-09-22 11:03:11