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[FIXED] PVM1454QM: horizontal collapse

A

Apocalypse

Hi all,

I have an issue with my PVM1454QM. It's almost like new (~1200h), yet a couple of months ago it shut down while playing.
Then I could hear the PSU clicking every second (cycling in safety mode).

I found out it was due to a short on 115V rail on the A board (main board) from a bad Q501 (D1397). I also preventively replaced its driver Q502 (C268B).
Also running the Q board (PSU) disconnected from the A board I measured 155V instead of 115V. This time IC602 was blown (STR-S3115), again I preventively replaced IC601 too (STR-M6524).

The problem is the screen is still not fixed. 115V is now stable but there's horizontal collapse.
At first image is fully displayed then within seconds it collapses to a single vertical line and the aforementioned components blow again.
Here's the pattern I observed:

1613390824699.png

Horizontal deflection coil has been mesured OK (~3 ohms).
115V is stable during the collapse then jumps to 155V when components blow.
Could it be a problem with the B+?
 
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Have you already checked the others psu rails, on pvm 20m2 m4 there is a 5v ic regulator wich often fail alongside with the hot and another ipower regulatot ic
 
Mukuro_W said:
Have you already checked the others psu rails, on pvm 20m2 m4 there is a 5v ic regulator wich often fail alongside with the hot and another ipower regulatot ic
Click to expand...
Yes indeed, all good.
Also checked the pincussion circuit since it's injected in parallel of the horizontal deflection (damper diodes D502/D512, also D506, Q503, etc.) all good too.
 
If you have already checked the two dumper diodes then there is also an ic wich provide E/W control , if my memory help, it is the ic 509 , should be a LM3580, in the past I have repaired a 2054 with weirdo pincushion issues and just was this ic! You should use a hot air station to rework this..
 
Mukuro_W said:
If you have already checked the two dumper diodes then there is also an ic wich provide E/W control , if my memory help, it is the ic 509 , should be a LM3580, in the past I have repaired a 2054 with weirdo pincushion issues and just was this ic! You should use a hot air station to rework this..
Click to expand...
I thought about it too, it's a LM358 in SOIC8 package, I have spares handy, also a hot air station, only thing is it's hidden in between chemical capacitors I'll have to remove first I think.
 
And yes you should but I din't , I have covered them with an alloy foil then removed the ic, basically I have cooked them :) this worked anyway. Removing the lytics caps and replace them is also a good idea since in that area they often fail due to heat gen between the v. Blanking ic heatsink and the HOT heatsink...
 
Do you think it could otherwise be a feedback issue or failing flyback?
 
I have lots of those PVMs, beleave me your flyback is ok!
 
Pvm 20m2, 20m4 2054 1454 1450, are all veriy reliable BUT, could happen that some psu ics fail alongside with the HOT and one of the two v. Transistor. More common is the 5v regulator wich release the monitor just dead with tally light on, another issue is the 200v line just near the flyback when a fast recovery diode fail alongside an inductor and cause a one dot at center of the screen at shut off and if not cuered just burn the screen pretty well after a second attempt . ... Now after replace the hot do you still getting h collapse? I think you have an issue in h stage . On one of my unit I have first fixed the psu than replaced the hot but got a weirdo pincushion issue wich could not be adjusted by OSD, turned out it was just this ic 509, I remember that there was also h amp issue but not a fully h collapse.
 
As said in first post I fixed the PSU (IC601 & IC602) and the A board (Q501 & Q502) but the problem is stil there and if I let the collapse go, IC602 and Q501 just blow again.
 
Ok test all the polyester film caps on h stage there is one wich can cause this if just go out of is spec more than the 5℅ it's rate, also investigate into your psu board for components leaking
 
Mukuro_W said:
Ok test all the polyester film caps on h stage there is one wich can cause this if just go out of is spec more than the 5℅ it's rate, also investigate into your psu board for components leaking
Click to expand...
Do you have an idea what is its ref/position? Schematics for the A board on my PVM are in the 14M2 service manual.

PSU, like all the boards in that PVM are like new. Not even dust on them.
 
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While 1454qm and 14m2 are very similar they have a different power board, by the way, the good news is that I have 1450 with a burn in on screen, so I can dusmantle it and supply a power supply, already serviced with best lytics caps (nichicom ucy an uhe series only) fully tested and working and also a flyback tested and working both the same ones installed on 1454, the mainboard is suitable but the 1450 not have component and does only 65k warm color preset not 9200.. Still I hope to can help just repairing your because I cannot beleave it's a flyback issue, just near the hot and dumper diodes there are some film caps check them all.
 
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I think the component on the G board (PSU) blew because the HOT was shorted (grounding the 115V rail) and is thus just a consequence (not a cause).
Now all voltages are present and stable so the PSU board is fine to me.
Problem lies in the A board.

I have found the service manual for the 1454QM and while Q board schematics are the right ones, for the A board I need to use those from the 14M2 manual.
 
Mukuro_W said:
On one of my unit I have first fixed the psu than replaced the hot but got a weirdo pincushion issue wich could not be adjusted by OSD, turned out it was just this ic 509, I remember that there was also h amp issue but not a fully h collapse.
Click to expand...
Posting the solution in case it could help someone else (but all the PVM specialists told me they had never seen such issue): problem was a faulty IC509 (LM358 ) in the horizontal correction section.
It forced the HOT to be constantly driven closed and in those conditions it fails pretty quickly (matter of seconds), gets shorted and in a domino effect also takes the 115V rail with it.
 
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