Patient is a Maytag/Whirlpool/Kenmore clothes dryer. Not sure of exact model, doesn't matter. All boards are out of production.
Specific problem is a Maytag 8544799 / WP8544799 motor-control board, aka Diehl Controls 708879-05. Customer states the board "doesn't work, motor doesn't run". Not sure how the repairman made that assessment, or if it's even accurate. He can't get replacement boards, and the owner decided to buy a new dryer, so whether this board is the problem is speculation on his part. Again, doesn't matter.
I've been over the board looking for shorted drivers, missing voltage rails, all the usual stuff. All looks good so far. Nothing obvious.
The general construction of Maytag/Whirlpool/Kenmore dryers from this era seems to involve 3 control boards: (1) the console board with buttons and display, etc., (2) this motor-control board which is a small 3-phase VFD, and (3) a main control board. All these boards communicate on a 3-wire bus, which I have seen pinned out as Vdd/Vss/Data. So presumably UART or similar protocol.
Motor control board evidently does not power the bus, as all the data lines are dead except for a few residual mV. Not shorted, just not powered.
So now I'm curious, because we somehow need to fake this thing into life. Does anybody have experience with the data bus in these or similar units? Surely someone somewhere has compiled a list of commands which pass between boards to indicate status, turn-on commands, etc. I doubt it's very complicated, and if you eavesdropped on the bus while pressing the front console buttons, you could quickly find this data. As long as they didn't pull a dirty trick like encrypting the data (why?).
The repairman whom I got this from is ripping the other boards out of the (now scrap) unit, along with the motor in case there's current-monitoring where the unit will scram if it doesn't see a motor. And he'll get them to me eventually. So in theory I would be able to compile my own data. But that would only be for this and similar units, not for every machine out there. So just wondering if there's an existing database or website dedicated to this that anyone knows of. I know for other repair sectors there are collections of "dirty little secrets".
Thanks in advance.
Specific problem is a Maytag 8544799 / WP8544799 motor-control board, aka Diehl Controls 708879-05. Customer states the board "doesn't work, motor doesn't run". Not sure how the repairman made that assessment, or if it's even accurate. He can't get replacement boards, and the owner decided to buy a new dryer, so whether this board is the problem is speculation on his part. Again, doesn't matter.
I've been over the board looking for shorted drivers, missing voltage rails, all the usual stuff. All looks good so far. Nothing obvious.
The general construction of Maytag/Whirlpool/Kenmore dryers from this era seems to involve 3 control boards: (1) the console board with buttons and display, etc., (2) this motor-control board which is a small 3-phase VFD, and (3) a main control board. All these boards communicate on a 3-wire bus, which I have seen pinned out as Vdd/Vss/Data. So presumably UART or similar protocol.
Motor control board evidently does not power the bus, as all the data lines are dead except for a few residual mV. Not shorted, just not powered.
So now I'm curious, because we somehow need to fake this thing into life. Does anybody have experience with the data bus in these or similar units? Surely someone somewhere has compiled a list of commands which pass between boards to indicate status, turn-on commands, etc. I doubt it's very complicated, and if you eavesdropped on the bus while pressing the front console buttons, you could quickly find this data. As long as they didn't pull a dirty trick like encrypting the data (why?).
The repairman whom I got this from is ripping the other boards out of the (now scrap) unit, along with the motor in case there's current-monitoring where the unit will scram if it doesn't see a motor. And he'll get them to me eventually. So in theory I would be able to compile my own data. But that would only be for this and similar units, not for every machine out there. So just wondering if there's an existing database or website dedicated to this that anyone knows of. I know for other repair sectors there are collections of "dirty little secrets".
Thanks in advance.
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