Main > Monitor/Video Forum
Troubleshooting a WG 25k7191 no picture blowing fuse
princess prin prin:
To confirm that the culprit is indeed the regulator IC you could do a bulb test this way.
- Lift one end of jumper J27 from the PCB as shown in the pic (be careful not to damage the pad).
- Connect the bulb to the lifted jumper and ground (IC4 pin 1, jumper JB, big heat sink, etc.).
- Desolder C57 and connect (remotely with wires) the positive side to the lifted jumper (or other points on solder side connected to it) and the negative to a ground point (IC4 pin 1, jumper JB, etc.). In other words C57 needs to be in parallel with the bulb.
- Keep pin 2 of the flyback desoldered from its pad (or alternatively lift one end of the jumper to the left of J27).
- Voltage at the lifted jumper (or the side of R301 with the blue wire) must be 130V or the regulator circuit (most likely the IC itself) has a fault.
All this assuming your old and new ICs are STR30130 and not STR3130.
joej85a:
--- Quote from: princess prin prin on March 22, 2020, 06:10:30 am ---To confirm that the culprit is indeed the regulator IC you could do a bulb test this way.
- Lift one end of jumper J27 from the PCB as shown in the pic (be careful not to damage the pad).
- Connect the bulb to the lifted jumper and ground (IC4 pin 1, jumper JB, big heat sink, etc.).
- Desolder C57 and connect (remotely with wires) the positive side to the lifted jumper (or other points on solder side connected to it) and the negative to a ground point (IC4 pin 1, jumper JB, etc.). In other words C57 needs to be in parallel with the bulb.
- Keep pin 2 of the flyback desoldered from its pad (or alternatively lift one end of the jumper to the left of J27).
- Voltage at the lifted jumper (or the side of R301 with the blue wire) must be 130V or the regulator circuit (most likely the IC itself) has a fault.
All this assuming your old and new ICs are STR30130 and not STR3130.
--- End quote ---
Thanks so much Pin, I will give this a try. 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? Getting everything installed in the cabinet to do the bulb test is proving precarious. Thanks!
behrmr:
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.
joej85a:
--- 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.
--- End quote ---
Ok, and I got the Vr IC from arcadepartsandrepair which seems to have a good rep. Maybe just a bad one.
behrmr:
Peter is a good guy. He will replace the IC if it was truly bad.