68kMLA Classic Interface

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SE/30 Analog Board Blunder

Posted by: LaPorta on 2020-02-06 18:22:33 Just posting as a word to the wise. I re-capped my SE/30s analog board, and it is a revision F. I had previously re-capped a revision C from my other SE. I had assumed they were basically the same. I had noted, however, that several caps (notably, the 100 µf ones), were rated at 25V on the Rev. F vs. 16V on the Rev. C. I must have missed one: C25. I installed a 16V in there. I finished up the machine, powered on, heard the startup chime, and immediately a loud POP and explosion occurred. In the pic, you can see the remains of the exploded cap, with some of it plastering R4. Never seen an explosion in action; now I have. A reminder to all: even if you are repairing the same board type, different revisions may have different components. Check EACH one...and don't repeat my idiot mistake.

Posted by: superjer2000 on 2020-02-06 22:13:38 I've noticed the same thing but just assumed Apple upsized the voltage to provide a bigger margin.  Is it possible the cap was backwards?

Posted by: LaPorta on 2020-02-07 02:15:50 Anything is possible. I always triple check before I solder anything in. Could have even been defective. However, I realized that it was the only one that I hadn't adjusted for voltage (by accident). You are correct, it usually is just for bigger margin, but I wonder in this case.

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