Hello, it's been a while since I posted on this forum.
I have been asked to "take a look at" a circuit board from a backup power generator and to "see if [the circuit board] can be tested." The backup power generator is not currently working correctly and the people responsible for it (referred to as the "operators" from now on) suspect this control board.
The operators lost the manuals and documentation for the generator. The service company that is the prime point of contact tried sourcing a replacement circuit board (the board's original equipment manufacturer is still in business) but the generator is so old that the guy from the OEM laughed. I have been told the generator may be on the order of 40-50 years old. I have also been told that the operators suspect the board may be responsible for shutting down the generator if certain conditions are met (like a generator protective shutdown circuit).
Attached are two pictures of the control board (top and bottom) and my first cut at a complete, but messy reverse engineered circuit diagram. I dug up datasheets and traced each circuit to create this Visio diagram. It took a total of 7 hours to get to this version. I slightly cleaned up the diagram last night, but nothing was electrically incorrect so this is still accurate. I only have this version available to upload right now.
Given that I was not told (and I'm told they don't readily know ... though I have asked them to look into it) what kind of wires/circuits connect to each of the seven spade terminals on the control board, I am left to try and "back solve" what each terminal connects to circuit-wise. Through backsolving, I believe I have identified the following input and outputs.
Power Input
1x +28VDC & 0VDC GND Pair (Two Terminals)
Signal Input
1x AC Sinusoid (Two Terminals)
Output
2x +28VDC Discrete Outputs (Two Terminals)
1x Output Voltage Select (One Terminal)
What I am looking for is help understanding the signal processing and Op-Amp processing of the input sinusoid signal. I think I have the SCR output circuits pretty well covered, but the chain of events that starts from an input sinusoid, through what looks like antiparallel clipping diodes, into what I think is an inverted negative feedback op-amp loop (possibly with frequency gain constraints), then fed into a second op-amp loop (what I am considering still "input side" signal processing) before feeding an output signal towards two adjustments circuits with trim pots that influence the two output op-amps and their downstream SCR handling circuits.
Any help in explaining what's going on here in more detail would be greatly appreciated.
Thanks,
Robert
I have been asked to "take a look at" a circuit board from a backup power generator and to "see if [the circuit board] can be tested." The backup power generator is not currently working correctly and the people responsible for it (referred to as the "operators" from now on) suspect this control board.
The operators lost the manuals and documentation for the generator. The service company that is the prime point of contact tried sourcing a replacement circuit board (the board's original equipment manufacturer is still in business) but the generator is so old that the guy from the OEM laughed. I have been told the generator may be on the order of 40-50 years old. I have also been told that the operators suspect the board may be responsible for shutting down the generator if certain conditions are met (like a generator protective shutdown circuit).
Attached are two pictures of the control board (top and bottom) and my first cut at a complete, but messy reverse engineered circuit diagram. I dug up datasheets and traced each circuit to create this Visio diagram. It took a total of 7 hours to get to this version. I slightly cleaned up the diagram last night, but nothing was electrically incorrect so this is still accurate. I only have this version available to upload right now.
Given that I was not told (and I'm told they don't readily know ... though I have asked them to look into it) what kind of wires/circuits connect to each of the seven spade terminals on the control board, I am left to try and "back solve" what each terminal connects to circuit-wise. Through backsolving, I believe I have identified the following input and outputs.
Power Input
1x +28VDC & 0VDC GND Pair (Two Terminals)
Signal Input
1x AC Sinusoid (Two Terminals)
Output
2x +28VDC Discrete Outputs (Two Terminals)
1x Output Voltage Select (One Terminal)
What I am looking for is help understanding the signal processing and Op-Amp processing of the input sinusoid signal. I think I have the SCR output circuits pretty well covered, but the chain of events that starts from an input sinusoid, through what looks like antiparallel clipping diodes, into what I think is an inverted negative feedback op-amp loop (possibly with frequency gain constraints), then fed into a second op-amp loop (what I am considering still "input side" signal processing) before feeding an output signal towards two adjustments circuits with trim pots that influence the two output op-amps and their downstream SCR handling circuits.
Any help in explaining what's going on here in more detail would be greatly appreciated.
Thanks,
Robert
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