Re: 7844 power supply

Ed Breya

The last time I fixed a 7844 PS, it was fortunately just two or so rather large (100 or 220 uF 20V) Ta caps shorted, on the pre-regulator supply board, for the +/- 15V inside the PS module - the one inside the cage, just below the outer, upper, linear regulator board. It's a PITA to get to, but doable - if you take enough stuff apart, you can run it while opened up and make measurements. The fix is fairly straightforward, but there's very little space, so you'll have to get creative with alternative cap arrangements. I manged to do all the work from the component side, avoiding having to remove the board, which is even more a PITA.

If it's not those or something else like another Ta cap in the scope circuits, it could be the dreaded HV winding failure on the main transformer. Hope for the lesser grief.


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