Whirlpool Oven RBD306PDB7 display blank

Just wanted to make this knowledge available to others.
Our Whirlpool oven (model RDB306PDB7) crapped out the other day. Thought it was the typical "thermal fuse" problem (thermal fuse goes open and power is lost to the display/control). Took the front display panel off and checked the fuse (have replaced it once or twice before) and it was fine. NOTE: The thermal fuse ususally goes during a cleaning cycle.
Well, now it appeared to the be circuit board. Looked it up and it was going to be about $225 to replace. So, I took the circuit board off and looked it over carefully. Here's what I found.
There's a power resistor (12 ohm) that is weakly soldered to a 1N4007 general purpose diode (standing in the vertical position) that had come apart. Looks like they might have used some low temp solder that couldn't take the continued heat and cleaning cycles, as well as not creating a good mechanical connection first. I've seen similar problems on my 1997 Chrysler Sebring Convertible dash display.
The power resistor is mounted in the air (for heat dissipation) but the engineers didn't take into account the thermal transfer back to the circuit board through the leads. Here's where I found that the traces were lifted from the board from excessive heat.
I actually replaced the diode with a new one with longer leads so I could bypass the etches on the board and used the longer lead to replace the copper trace on the board (which I soldered much better than it had been). The lead of the resistor that went through the board actually ends up connecting to the display, so I ran a separate wire to overlay the trace for additional thermal dissipation. I then connected the resistor to this wire and the cathode of the vertical 1N4007 diode.
Unfortuately, I didn't take any pictures but perhaps others with a similar problem will be helped by what I found.
By the way, it's hard to believe the way this board was put together meets UL requirements. Seems kinda' dangerous.
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snipped-for-privacy@txwrights.com wrote:

Thai's impressive. Nice job.

UL probably didn't test the board per se. They usually test the whole device. If it doesn't catch fire or blow up it's 'listed'. So if you want tests, Consumer Reports is one source that will comment on performance or quality. Otherwise, it's a jungle out there <G>.
Joe
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