Weiya C3129D + Beijing-Matsushita a68mau085x90 Partial Vertical Collapse.

[jonsilvestro]

Hey folks, I've got a Sanwa PFX out of a Wangan Midnight 3 I'm having some issues with and I'm frankly at a loss for what to try next.

The chassis is a Weiya C3129D with a Beijing-Matsushita a68mau085x90 and I believe the original PFX yoke.

I've already recapped the whole chassis, I replaced the vertical deflection IC, I tested and replaced most of the passive components in the vertical deflection circuit, I reflowed most of the solder joints and tested them for at least continuity and I pulled the yoke to check for any corrosion, while I don't have an LCR meter to properly check the yoke I don't think its causing the issue.

What you see is all I've managed to get and it hasn't changed at all with any of those things I mentioned doing.

At this point I don't know what else to try, I don't have another tube, yoke or chassis on hand to test (with the exception of another C3129D that has a different chassis revision and I know is dead) I am trying to source something so I can at least narrow the problem down some though.

Has anyone else had a similar issue? Anyone else running the same chassis yoke and tube setup?

Any new ideas would be very welcomed and I'd be happy to provide any more information anyone thinks is pertinent and helpful to diagnose it.

Thanks!

 

[Big_P Big_p]

Have you checked the vertical supply voltage? Check you have 24v ish at the vertical IC then work your way back through the vertical circuit until you find it. The supply resistors can get put under quite a strain when the vertical IC goes so if you were not confident probing voltage when the chassis is live maybe test them out of circuit first.

 

[jonsilvestro]

Have you checked the vertical supply voltage? Check you have 24v ish at the vertical IC then work your way back through the vertical circuit until you find it. The supply resistors can get put under quite a strain when the vertical IC goes so if you were not confident probing voltage when the chassis is live maybe test them out of circuit first.

If I'm honest I can't remember if I did or not. At any rate I'll check it tonight when I get home from work and report back.

It is worth mentioning the IC I swapped into this chassis was from my other known dead C3129D but given the issue manifested in an identical way with both IC's and the other chassis while dead does not have the same issue I think its fairly safe to assume that the IC itself isn't whats causing the problem at least not on its own but it could still be the source of the problem.

 

[Big_P Big_p]

I just have to say only work on crt chassis at your own risk. There are voltages that can be lethal in there, so if in doubt, dont touch it. Unfortunately a lot of Chassis technicians won't work on these or other Wei Ya chassis.

If the vertical IC looks good and there isn't a short between Vcc and GND its worth getting a supply voltage reading. I suspect with symptoms like that, the vertical supply voltage is about 1/2 what it should be. You need to work out why.

I would start with a visual inspection of the vertical circuit. Paying close attention to and resistors, diodes or solder that looked iffy. Then once I was pretty sure I knew what connected to what, and where all my ground points are I would test the voltages in circuit.

 

[jonsilvestro]

I just have to say only work on crt chassis at your own risk. There are voltages that can be lethal in there, so if in doubt, dont touch it. Unfortunately a lot of Chassis technicians won't work on these or other Wei Ya chassis.

If the vertical IC looks good and there isn't a short between Vcc and GND its worth getting a supply voltage reading. I suspect with symptoms like that, the vertical supply voltage is about 1/2 what it should be. You need to work out why.

I would start with a visual inspection of the vertical circuit. Paying close attention to and resistors, diodes or solder that looked iffy. Then once I was pretty sure I knew what connected to what, and where all my ground points are I would test the voltages in circuit.

I definitely know the dangers to my cost after my WG D9400's flyback bit me haha.

I'm curious why a lot of techs won't work on these weiya chassis though, are they just garbage and thats why?

I'll measure and inspect as much as I can and get back, I ended up getting busy last night but I should have time to work on it again tonight.

 

[Big_P Big_p]

I don't really know why some guys won't work on these. There are NOS ones selling for $120usd plus shipping occasionally but often the caps are dry and the die quickly anyway. So maybe they figure the ate not worth it.

I know I just got 2 of these and I think its actually 4. None of which appear to work so maybe they are not good. But all chassis are getting to an age where stuff goes wrong. Ill get them working somehow. Hopefully yours gets going too.