[sebhc] H89 strange problems....

Lee Hart leeahart at earthlink.net
Wed Jan 18 22:17:39 CST 2006


Paul A. Pennington wrote:
>     Robin;
>
>     Those are hum bars in your video, and your troubleshooting is in the
> right area -- the power supply.  One weak point in these units is the
> bridge rectifier.  It's the large one in a metal case with four push-on
> terminals. Replace it with one rated for higher current.
>
>     While you're at it, replace the connectors with soldered connections to
> both ends of the wiring to the bridge.  The molex connector would
> frequently fail from overheating due to the current it carried.  Soldering
> the wires to the bridge and the circuit board will remove this as a future
> problem.

Very close! Robin, open the case and look at P101, the white 8-pin connector 
at the rearmost edge of the little power supply board, directly under the 
fan. You will see two yellow wires. I'll bet you this connector is getting 
hot and discolored around those yellow wires. The connection is going bad, 
adding resistance and voltage drop, so the 5v regulator is not working 
properly.

The (Heath approved) fix is to cut the two yellow wires going to P101, and 
connect them directly to the AC input terminals of the bridge rectifier. This 
takes 4 connectors out of the path from transformer to bridge, greatly 
reducing heating and voltage drops (and incidentally eliminating your hum 
bars).
-- 
Lee A. Hart    814 8th Ave N    Sartell MN 56377    leeahart at earthlink.net
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