Sony PVM 14M2MDE - Vertical Collapse - Help Needed!

[daveyheats]

Hi all, hoping to get some help on fixing this Sony PVM 14M2MDE before I throw both it and myself out the window.

I bought it a couple of months ago as faulty with vertical collapse / no power at all. By replacing the components listed below she's now got power again, but still vertical collapse in the form of a thin blue line.

So far I've done the following:

A Board
- reflowed lots of joints, particularly all ICs, caps, connectors, flyback
- replaced all caps in the vertical section (list of caps from RetroTech)
- replaced Difrection IC chip (NEC PC1377C)
- Replaced and/or tested Q501, Q512, Q515, Q520
- Replaced C537 and R541, which I've seen have caused collapse on other PVMs.

Power Board
- recapped all caps other than large filter cap
- replaced 3 or 4 of the ICs.

I'm pretty handy with soldering, but it's the diagnostic part that I'm still learning, so any advice on what I can test, where and how would be massively appreciated. Hence why the above list of parts has been a total shotgun approach to the problem.

I've seen people on here in the past have success repairing these, so praying I can do the same!

What does worry me is the main board has been worked on before, and very badly, so I'm trying to clean up / repair what I can. I just hope this hasn't caused the issue.

[MKL]

You have vertical collapse but horizontal/flyback/high voltage work so next time leave Q501 alone.

The vertical part of IC507 does need 12V but it's not the 12V line from Q520, it's the one from the 7812 regulator IC505. You can follow the trace from IC505 (3) to IC507 (21). Check for 12V on pin 21 or on the leg of R592 connected to it. If there's no 12V, check on the other leg of the resistor. If it's there, the resistor is open.

The vertical output circuit uses a 24V supply from the flyback. Check for this voltage on the anode of D530.

And the first thing to check is the vertical deflection coil. If it's open (not likely but it can happen) you can check that easily. If it's good you move on to the chassis. Unplug the yoke connector and measure the resistance across the wires that are not red and blue. If you have some resistance the coil is OK.

Other things would require an oscilloscope.

Why didn't you check Q513 too?

[daveyheats]

Amazing, thanks so much for the pointers, I know where to start investigating now! Will report back with my findings, but thanks so much for giving me hope!

Oh, and I forgot to mention I actually replaced Q513 too in my shotgun part replacement spree.

[daveyheats]

Just checked the vertical coil resistance on the connector and.....nothing. So this means the coil has a break in it somewhere I'm guessing

Hoping it's a visible break in can repair

[daveyheats]

Ignore that, just tried again and getting 18.4ohms between brown and yellow line, so coil panic over!

[daveyheats]

You have vertical collapse but horizontal/flyback/high voltage work so next time leave Q501 alone.

The vertical part of IC507 does need 12V but it's not the 12V line from Q520, it's the one from the 7812 regulator IC505. You can follow the trace from IC505 (3) to IC507 (21). Check for 12V on pin 21 or on the leg of R592 connected to it. If there's no 12V, check on the other leg of the resistor. If it's there, the resistor is open.

The vertical output circuit uses a 24V supply from the flyback. Check for this voltage on the anode of D530.

And the first thing to check is the vertical deflection coil. If it's open (not likely but it can happen) you can check that easily. If it's good you move on to the chassis. Unplug the yoke connector and measure the resistance across the wires that are not red and blue. If you have some resistance the coil is OK.

Other things would require an oscilloscope.

Why didn't you check Q513 too?

Evening buddy. I've just checked the PVM and got the following readings on those areas you mentioned to test:

Have continuity between leg 3 of IC505 and leg 21 of IC507.
18.4ohms between brown and yellow wires on yoke connector block.
R592 reading 10ohms tested in circuit
Leg 1 of R592 reading 12v
Leg 2 of R592 reading 11.85v
Anode of D530 reading 28.65v


Do all of the above sound OK / around where they should be? And if so, what would you investigate next?
Thankyou so much for your help, it's massively appreciated.

[MKL]

All of that checks out fine.

Measure voltage at the cathode of D528. It should be about 50V.

Check R1531 and R1528.

If it only would be possible to see if there is a sawtooth on pin 15 of the uPC1377...

[daveyheats]

Hiya. Just measured those points:

cathode of D528 reading 27.4v
R1531 measuring 55.4ohms
R1528 measuring 0.989k ohms

The two resistors seem bang on the specs in the service manual but looks like D528 is less than half what it should be?

Oscilloscopes terrify and intrigue me in equal measure

[daveyheats]

I've also just discovered SavonPat recommends changing C584 to a 4.7uf 160v cap which I replaced over the weekend, but still only reading 24.7v on D528. Any other ideas where to check next?

Thanks so much for your help so far MKL, you're a hero!

[daveyheats]

Just been through and replaced and / or checked all resistors and caps around the pump up diodes and still only have 27.4volts on D528. And obviously still vertical collapse!

It's driving me mad! Any other suggestions on what I can check would be amazing.

[jd213]

This might be a long shot, but a film capacitor was bad in my Olympus OEV143 (M2 rebadge), so it might be worth checking the ones in the deflection area.

[daveyheats]

This might be a long shot, but a film capacitor was bad in my Olympus OEV143 (M2 rebadge), so it might be worth checking the ones in the deflection area.

Thanks buddy, that's definitely something else to look into. Do you remember roughly which cap went on yours?

[jd213]

Yeah, it was C2510, although not all M2 series models have this specific one populated. Here's the thread where MKL helped me diagnose it, his knowledge of this series is amazing, despite my idiotic bumbling on display (I've since improved my general experience a bit, but not that much): viewtopic.php?p=1483598#p1483598