OK, I got a UPS from the local school corporation that they were going to toss out. Eaton Powerware 3105. I have found by checking the board that it's only getting ~8VDC where it should be getting 12. This in turn seems to be causing a relay not to work. The thing is, I couldn't figure out where the heck the DC voltage was supposed to be coming from.
No rectifier in sight anywhere. Upon closer examination I found the DC voltage leads traced back to the big honking transformer!! Do they make transformers with built-in rectifiers? I had no idea there was such a thing. So if I'm only getting 8V out, I probably have a damaged rectifier or shorted transformer winding, eh? Can these be serviced at all? Or is the only fix a replacement?
There are (2) 16AWG 120V input wires, a black and a white; (4) 10AWG wires, a red and black going to the backup battery (with transformer hooked to 120VAC and backup battery disconnected, I'm getting 3VAC output on these, short?), and a black and white going to 2 sets of paralleled 9972GP FETs, with 120VAC into the transformer and backup battery disconnected, these wires output 16VAC. There are also (3) more 16AWG wires coming out, a red, black and white. As near as I can tell, the white and black are carrying AC @ 8V each, and the red is a common or ground. Both white and black check 8VAC w/respect to the red, and 16VAC with each other. I'm thinking they should be 12VAC and combine for 24? I'm digging for a schematic now. Edit: looks like the red should be carrying 12VDC, it has 8VDC with the backup battery plugged in, 0V without. These wires are at J5 on the schematic. Looks like CT1 shows where the DC is coming out of the transformer.
OK, found a schematic, here's an image of it:
No rectifier in sight anywhere. Upon closer examination I found the DC voltage leads traced back to the big honking transformer!! Do they make transformers with built-in rectifiers? I had no idea there was such a thing. So if I'm only getting 8V out, I probably have a damaged rectifier or shorted transformer winding, eh? Can these be serviced at all? Or is the only fix a replacement?
There are (2) 16AWG 120V input wires, a black and a white; (4) 10AWG wires, a red and black going to the backup battery (with transformer hooked to 120VAC and backup battery disconnected, I'm getting 3VAC output on these, short?), and a black and white going to 2 sets of paralleled 9972GP FETs, with 120VAC into the transformer and backup battery disconnected, these wires output 16VAC. There are also (3) more 16AWG wires coming out, a red, black and white. As near as I can tell, the white and black are carrying AC @ 8V each, and the red is a common or ground. Both white and black check 8VAC w/respect to the red, and 16VAC with each other. I'm thinking they should be 12VAC and combine for 24? I'm digging for a schematic now. Edit: looks like the red should be carrying 12VDC, it has 8VDC with the backup battery plugged in, 0V without. These wires are at J5 on the schematic. Looks like CT1 shows where the DC is coming out of the transformer.
OK, found a schematic, here's an image of it:
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