Retrofitting a 1986 Maho MH400E

No I am wrong. The 19k1 should energize as soon you press power bouton in gmoccapy.
John

Yes, that's the problem. I can solve it by moving the wire to the 7i77 but now after what PCW said I'm afraid not to damage that board. I would very much like to know what happened before I move forward, and yet I don't really have any time to do so. This machine must be up and running ASAP or my little operation is going to be in serious trouble.

By the way, don't these 7i84 have overvoltage protection and whatnot? Would one really get damaged from outputting 24V with only one bank of field power connected? Should I order a new board while EU surplus has them in stock?

It says in the manual that if only one power source is present, the card shouldn't work. But mine did. Also, CR7 is green in LCNC and CR6 is off, I don't know if there's any other indication of field IO faults. HAL shows pins. It looks like the board is okay, so why doesn't it work?

I don’t think you have damaged the board, chances is that you have make a mistake in hal syntax and the output is not energized. Try to energize a not connected output of the board and use a multimeter and see if there is 24 volt out.

I dont think a unconnected field power would cause damage but its not an expected mode of operation.

The 7I84s output drivers have short circuit protection and inductive flyback
protection but there are things that can damage the outputs:

1. Driving inductive loads larger than about 60 mA that have no flyback diode.
2. Switching the field power power with a switch or relay (this can cause
a voltage surge that exceeds the voltage rating of the output chips)