Main > Monitor/Video Forum
Troubleshooting a WG 25k7191 no picture blowing fuse
joej85a:
--- Quote from: joej85a on March 22, 2020, 11:55:09 am ---
--- Quote from: behrmr on March 22, 2020, 11:48:09 am ---It's best to connect everything except for the video input when you power the chassis.
As for your faulty regulator there are a lot of conterfeit IC's out there so check your source.
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Ok, and I got the Vr IC from arcadepartsandrepair which seems to have a good rep. Maybe just a bad one.
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That is what I had read. My guess is something on the board cooked it. I have ordered a new one, and will try the bulb test before I try it in the full circuit. My fear is that something on the board is killing the regulator and I won’t know until I try it again. I omhed it out via the FAQ sticky and it was all over the place, so it’s shot for sure.
Also, Pin, thanks for the further test info. I will try that just to verify.
princess prin prin:
--- Quote from: joej85a on March 22, 2020, 10:22:02 am ---Can you verify if for the bulb test I can just hook up to the power from the isolation transformer and forego the other connections for the chassis?
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If you follow my instructions the voltage regulator circuit will be completely separated from the rest of the chassis so power is all it needs.
joej85a:
--- Quote from: princess prin prin on March 22, 2020, 01:51:22 pm ---
--- Quote from: joej85a on March 22, 2020, 10:22:02 am ---Can you verify if for the bulb test I can just hook up to the power from the isolation transformer and forego the other connections for the chassis?
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If you follow my instructions the voltage regulator circuit will be completely separated from the rest of the chassis so power is all it needs.
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Okay so quick update. I took Pin's advice and isolated the regulator IC per the instructions posted. Pulled the jumper, wired C57 in parallel and hooked up the bulb, and got a reading of 160.2vdc at the jumper leg. So the new regulator IC4 is toast. Just for fun, I soldered the original regulator IC back into the board and did the same test, got a reading of 162.4vdc, so the old one is toast too. Not real surprised there, but is it odd they both failed and apparently in the same way that pushed them up to 160vdc? My input voltage from the isolation transformer is 128v.
So as I said before, new regulator is on the way. But does this give me any direction? Assuming the new one goes in and I test it as above, and I get a good 130vdc, what is the best next step to avoid toasting regulators over and over?
Again, thanks all for the sage advice, I do appreciate it and other than the annoying chasing ghosts, it has been a fun process so far. Looking forward to seeing it fire up.
princess prin prin:
The circuit of your last test is like this. There isn't much that can be at fault. Check the three electrolytics (C55, C56, C57), the resistors and then there is only the IC left.
joej85a:
--- Quote from: princess prin prin on March 23, 2020, 08:49:11 am ---The circuit of your last test is like this. There isn't much that can be at fault. Check the three electrolytics (C55, C56, C57), the resistors and then there is only the IC left.
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Thanks Prin, I will check the above. All the caps are new, so I am hoping no issue there. I did order new resistors when I ordered the regulator, so now it is just a "wait until they arrive" scenario.