I have had a similar adventure twice with my 962. Both times
I had a shorted diode in the bridge rectifier. The easiest
way to troubleshoot has been to lift both the large black and
large red leads from the board. Now, with a new fuse, fire it up.
You should measure a clean DC voltage in the 16-18 volt neighborhood.
I suspect the fuse will blow again though. At that point, doccument
all of the wiring and remove the filter cap board. By unsoldering
the 2 large yellow leads )red & black still disconnected)from the
transformer you can now check the bridge diodes with an ohm-meter.
I ordered the bridge rectifier from Ten Tec the first time. The cost
was around $7 or $8. The second time around I had more things I
needed so I ordered from Allied Electronics. Their cost was $5.50
for the bridge. I got a good gooey heat sink paste to put between
the bridge and stocked up on fuses. I also got a spare bridge
thinking if I have a spare, I'll never need it! :-)
Here is what I think happened to my first repair. The heat sink
compound was a Vaseline-like silicone grease for heat sinking. It
appears that between the heat from the transformer and the bridge
rectifier, the heat sink compound oozed out as I had a large film
of it migrate. Without the compound there, it overheated and failed
about 6 months later. We shall see how this repair went. Another
area of concern is soldering temperature. The wires and bridge lugs
are quite massive. Selection of a soldering weapon that gets the
junction heated enoughbut not so that it overheats things is a
challenge.
Carl R. Gansen WB0CFF
9300 W 225 St
Belle Plaine, Mn. 56011-4206
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