I too had a failure of the bridge rectifier some years ago. I don't
recall finding much if any heat sink compound under the bridge assy upon
its removal. In replacing the unit, I use some of the white heat sink
compound, less is best in this case, and never again have I had a
problem.
73
Bob K4TAX
Carl R Gansen wrote:
>
> 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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