Electronics > Repair
EC motor with modbus, inject DC
MartinFO:
Hi
I have multiple EC fan motors that operate at 400V AC. The IGBT is fried and powering the EC via 400V just trips the relay. The fan have Modbus communication which can be used to readout a log file, which is important to find the root cause. I suspect that I could somehow power the low voltage logic of the PCB by "injecting power" somewhere and establish modbus communication. It is difficult, since the main PCB is covered with potting compound.
I have tried the obvious of applying power to the 24V output on the small add-on PCB. It works somewhat, since the status LED (on the small PCB) starts flashing with the error code "internal communication error". I would assume there is a diode somewhere that prevent the main board being powered. I have also tried powering where the small PCB is connected to the main PCB, but I get the same result as via the 24V output. Is there is better place to try? The board is already fried, so it is not a problem to break components to gain access.
croaker:
Try to dismantle the board and remove the compound by heating it (with a hair dryer or in an oven).
MartinFO:
Good suggestion, but I have tried that. The compound is impossible to remove. I have tried alot of different methods.
I have thinking about breaking one of the capacitors off and power the exposed leads?
langwadt:
what on the JST connector?
croaker:
You can try to remove the compound chemically. I use this paint remover, it also removes epoxy compounds.
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