AS much as I like my custom controllers I just can't pass up a challenge. The other day I'm cruising ebay and stumble onto a control board for the Whit ADV 2 T and the price was dirt cheap at $27 and free shipping. Write up says "Was changing settings and something sparked, then nothing" Hmmmmm. For that little $$$ this might be an interesting thing to fool with. Board got here last night and I ripped the face plate and back shield off to get a good peek at the thing. Got out the mag visor and a strong light and looked the unit over well. A couple solder joints showed signs of heat (100 ohm resistor at the joints) Resistor check the same as surrounding ones with the same color codes (100 ohms) Continued to look for something that might explain the "SPARK" Then I spotted the offending little gremlin. A TANTALUM capacitor, well what is left of it anyway. The little yellow component is blown all to rat chit with very little of the yellow coating left and the two stubs still soldered to the board. No signs at those solder joints of excess heat either. Pulled the board from my spare to see what the thing is supposed to look like and get some nomenclature off it. OK I needed to discern which leg was the + as these must be connected correctly. Got that. Now for the writing on the cap It is a bright yellow has an L shaped line with the + at the end of the leg then there is 22u (will assume 22 microfarads) and under that is 16 Now my area of expertise is not so much in micro electronics, but rather heavy machinery wiring. Did not research on this little beast and discovered that it is a Tantalum capacitor and that these critters can go poof. Any of you troops here that fool with electronics please chime in At present the plan is to replace the one resistor that shows excess heat and bridge the traces to be sure the connections are good. Then replace the cap. I suspect the stove may have been hit by a power surge once upon a time that possibly weakened the cap and then it let go. Further snooping reveals that the circuit is tied in with the combustion fan. The trimmer pot for the comb fan feels horrible and there is a circuit trace that is burned leading from the pot. I suspect that the items involved are all connected to possibly a failing/failed combustion fan motor. Without a detailed schematic of the board it will be tough to really tell wasssssup (At least without a lot of work work) I can remove the carnage and jumper the burnt traces with small hard wire. Replacing the cap and the resistor is no biggy either. This is the very reason I hate these all in one micro electronic boards. I was told a few years ago that if any of the motors short it wipes out the board, period, and I suspect that this is the very result in the flesh. Very interesting, indeed. Gonna give it a go and see if I can repair it. Sadly it means taking several things off the board to gain access to the damaged traces. The very reason I went with components that are way tough and the fuses are between the feed and the component and will blow long before the important stuff goes poof. Off we go on another dammed fool crusade.
While you are at it, you may want to teplace the electrolytic caps. They can dry out over the years and the stop dojng what they are supposed to. Have a tv where i had to replace the caps in the power supply. Since they "got weak", they let too much ripple past and the electronics in the hi def tuner (also has a microcontroller in it) didnt like. Tv failed to finish "booting". New caps for 30ish bucks and tv works like new.
My big worry is the two traces (very small) that connect to the cap and the trimmer are wasted I can jump these out with small hard wire Got to remove the room fan pot from the board to get at the one traces termination buttttttt With the IC right in there too, so wondering if any of that stuff is fouled too The tabtalum 16 volt 22uf cap is 59 cents The small wire to jumper the traces is pennies I'm betting the thing may have been hit with a power surge once upon a time and the cap was wounded When it was in its death throes it took out the other stuff I sent the seller a mssg asking if the new board he bought fixed his stove If he had other issues a new board won't fix it Be interesting to hear back from him
Pic of fried cap And the resistor terminals showing signs of heat My feelings are to relpace the Cap, resistor, the one trim pot and wire around the burn traces and then see what happens Worst case scenario is it will fail again I really think the cap just died taking stuff with it Watched some u tube vids on a tantalum cap exploding Real cool fire works
Looking over the board more and I think I got everything scoped out. Went to fry's and got the parts needed (Caps, diodes etc) Still need two trim pots as the ones for the two fans are not working at all, just do zip on my VOM The pot for the auger works fine. The guy who owned the board emailed me back and his stove works fine with just a board swap, so the board had the issue. I can fix the damaged traces, replace the resistor and the capacitor, but I have no real way to tell if any of the IC chips took a hard enough hit to fry their brains. Guess we will do the R&R on the parts and then see WASSSSUP.
