I have an issue with my Sanyo 20ezv that I pulled from a Donkey Kong cabinet. Several hours of work have been put into it, but I am thoroughly stumped and it's time to turn to some external help. Our problem began with a monitor that was strictly in vertical collapse, and after a lot of probing we found that the ceramic block resistor at R414 was barely hanging onto the pad. After fixing that, the problem became one of a vertical foldover that I have never seen on a 20ez. Things voltage-wise are slightly off starting directly downstream of R414, so that has been our biggest focus area, but no dice so far after many replacements and measurements. I would happily check out/replace any part or connection again if anyone has an idea.
Part replacements and measurements (see image as well):
Every electrolytic on the board.
The entire parts list from the 3, 4, and 5 pin circuit off of IC401. This includes the three transistors (TR401, 402, 403) twice, capacitors, resistors, diodes, germanium diodes, thermistor, potentiometers.
IC401 itself has been removed and replaced with one from a confirmed-working donor board.
All of the components in the vertical circuit have been reflowed at least once. This includes several pads that were in rough shape when we got it, that were lifted and needed to be fixed in one way or another. However, all of the problem spots have been measured for continuity to confirm their status.
The rest of the board was visually inspected and several more pads were reflowed.
The wires from the pots to the pot control board have been tested for continuity.
The green and yellow vertical coil wires have been tested for continuity.
The resistance of the vertical coil was measured at 54.7 ohms.
Voltages (see image as well):
B+ measures 108 at low brightness after a slight adjustment.
After R414 measures lower than our working board (a smaller model, so not necessarily a good indicator.)
Voltages seem quite low downstream of the emitter of TR402. We have replaced TR402 twice, so I'm doubtful this is the problem.
Readings continue to be low in the <3>, <4>, and <5> line. This assumption is based on our only other reference which is a different model, so it is not necessarily a problem. However, the voltage on pin 3, 4, and 7 of IC401 do not match the troubleshooting guide's values.
Notes:
I did notice that the three vertical transistors each have two versions listed. I could not find a key for what (D,E) or (O) means, so I just bought the top transistor listed for each. They seem similar on their respective spec sheets.
We have not checked out the neck board at all. I know that there is no red present, probably the transistor on the neck. I am not too worried about this for now, though.
The yoke visually looks fine and the convergence seems fine as well.
We have not done any current measurements.
Can get different/better pictures if needed.
Part replacements and measurements (see image as well):
Every electrolytic on the board.
The entire parts list from the 3, 4, and 5 pin circuit off of IC401. This includes the three transistors (TR401, 402, 403) twice, capacitors, resistors, diodes, germanium diodes, thermistor, potentiometers.
IC401 itself has been removed and replaced with one from a confirmed-working donor board.
All of the components in the vertical circuit have been reflowed at least once. This includes several pads that were in rough shape when we got it, that were lifted and needed to be fixed in one way or another. However, all of the problem spots have been measured for continuity to confirm their status.
The rest of the board was visually inspected and several more pads were reflowed.
The wires from the pots to the pot control board have been tested for continuity.
The green and yellow vertical coil wires have been tested for continuity.
The resistance of the vertical coil was measured at 54.7 ohms.
Voltages (see image as well):
B+ measures 108 at low brightness after a slight adjustment.
After R414 measures lower than our working board (a smaller model, so not necessarily a good indicator.)
Voltages seem quite low downstream of the emitter of TR402. We have replaced TR402 twice, so I'm doubtful this is the problem.
Readings continue to be low in the <3>, <4>, and <5> line. This assumption is based on our only other reference which is a different model, so it is not necessarily a problem. However, the voltage on pin 3, 4, and 7 of IC401 do not match the troubleshooting guide's values.
Notes:
I did notice that the three vertical transistors each have two versions listed. I could not find a key for what (D,E) or (O) means, so I just bought the top transistor listed for each. They seem similar on their respective spec sheets.
We have not checked out the neck board at all. I know that there is no red present, probably the transistor on the neck. I am not too worried about this for now, though.
The yoke visually looks fine and the convergence seems fine as well.
We have not done any current measurements.
Can get different/better pictures if needed.