[TenTec] Power Supply problem

Carl R. Gansen wb0cff@hotmail.com
Wed, 18 Apr 2001 04:04:13


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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