Ollie's PVM Giveaway Repair Thread

The Last Bandit · 11-03-2022 9:32am

What did you replace the internal fuse with ? Must have been rated too high to blow the other fuses

Colonel Panic · 11-03-2022 9:43am

That’s the weird thing. I used a 4A fuse listed upthread.

KeRbDoG · 11-03-2022 8:33pm

Sounds like the PTC is a solid place to start - pop it out, replace that fuse(s) and see if the monitor comes alive :D

KeRbDoG · 11-03-2022 8:38pm

https://www.boards.ie/discussion/comment/118616264#Comment_118616264

Might you have any photos of your internal RGB mod you can share?

Inviere · 11-03-2022 9:23pm

Those PTC's from eBay arrived, all seemingly used with solder on the legs despite being listed as new old stock. Full refund given (same as the Polish two pin ones, also refunded.)

I don't think I'll take a chance fitting one of these Spanish ones, i can't find them listed on any datasheets anywhere, and don't want to cause further issues by chancing one of them.

So still at square one here. I've ordered some 9ohm 3 pin ones from Ali Express, but eta is June. If anyone has a spare or two that are verified working, I'd happily pay 👍

The Last Bandit · 12-03-2022 10:44am

Using a DIN 8 for the inputs, a SCART socket would just about fit.

Board with input capacitors & resistors hanging of the input socket, brown & white wires are the audio and purple is the RGB switching

First attempt using unshielded wires, lot of noise but probably was the sync wire picked up the noise - yellow wire in this picture.

Changed them all to shielded cables, probably not necessary for the RGB.

KeRbDoG · 12-03-2022 1:24pm

Cheers for the photos, I was considering mounting a SCART socket or lots of BNCs but the 8pin DIN makes more sense - then I can make a DIN->SCART or BNCs as needed

The Last Bandit · 12-03-2022 3:57pm

Yep I just made up a short DIN->SCART cable which does the trick.

Colonel Panic · 12-03-2022 4:29pm

Looks really neat!

o1s1n · 14-03-2022 4:47pm

I absolutely hate you all for making this kind of thing look so easy! Haha

Colonel Panic · 14-03-2022 8:40pm

https://www.boards.ie/discussion/comment/118769951#Comment_118769951

Yep, may as well have a look. I've tracked the part down on the service manual so hopefully I'll get time over the long weekend.

KeRbDoG · 04-04-2022 8:01pm

PTC components arrived today so installed it in the monitor which turned when I had removed its original PTC

Installed!

Boom! Working...albeit with composite input for now

Inviere · 04-04-2022 8:27pm

@KeRbDoG where did you buy those ones?

KeRbDoG · 04-04-2022 8:28pm

https://www.boards.ie/discussion/comment/118880525#Comment_118880525

I think it was linked to before, but the 3pins 9ohm variant on this AliExpress listing

https://www.aliexpress.com/item/32947716849.html

The Last Bandit · 04-04-2022 8:37pm

Result :)

Hopefully mine should be here shortly as well so I can repair the donor TV..

KeRbDoG · 04-04-2022 9:11pm

I replaced the PTC in the other monitor I had and the set did the same as before - powered on and right back off and won't do anything if you switch it off and on. No LED, no funky turn on CRT noises or anything. Need to leave it for a time and then it will do the same half turn on and dead again.

I tried the hold Menu/Chroma diag feature when I know the set will power on for a second but nothing. Maybe a protection circuit? No idea what to check if thats the case.

Update: Simple idea dawned on me, I could just start swapping boards with the good monitor to narrow down the problem. Its most like the main PCB but this would at least narrow down the issue.

The Last Bandit · 06-04-2022 9:23am

Given those symptoms it sounds like the x-ray protection is kicking in alright, this is triggered by the HV being too high or the x-ray protection circuit is faulty, excessive high voltage is a lot more likely though.

Possible causes of the excessive HV are a B+ being to high so a dodgy low voltage regulator. Bad caps around the HOT, don't have the schematics to hand so can't suggest ones to test now. Bad Hsync drive circuit screwing up with the HOT timing. I've test the B+ and caps first as there probably the easiest sort out.

You could swap the main boards but tbh there is nothing on the neck or input board that should cause this type of failure.

There are probably a load of other components that could cause the failure, but the above are the most likely given the stress the HOT and caps are generally under.

KeRbDoG · 06-04-2022 5:00pm

Slightly faster schematics than archive.org

JVC TM-H140PN Service Manual_.pdf

Cheers for the info - I'll start to hunt around the HOT for dodgy caps - nothing 'looked' bad but who knows

eddhorse · 07-04-2022 9:23am

@KeRbDoG

Looks like a 3 and a half star monitor 😜

How many stars did the other broken monitor have?

Great work nonetheless, also still waiting on Aliexpress delivery

KeRbDoG · 07-04-2022 2:48pm

https://www.boards.ie/discussion/comment/118892615#Comment_118892615

The monitor which I couldn't get working indeed has no stars - I should have known it might have been a dud :D

I've tapped the person who I donated the other screen, to see if they want me to take a look so hopefully I can get 2/3 of them work with the PTC replacement

eddhorse · 11-04-2022 9:39am

Waiting for Ali Express components

Inviere · 11-04-2022 9:44am

Yep, same. SLOOOOOOOOW

eddhorse · 14-04-2022 10:28pm

Arrived today, 5 PTC replacements finally. Going away for the weekend though so won't get a chance to look at it until next week. Will post out the spares if I fix it.

The Last Bandit · 15-04-2022 11:35am

New PTC's turned here as well and do work ok in the JVC, didn't work in the donor Daewoo though (must lower heater resistance so just overheated) so had to put the original one back in.

The seem to take a while to cool down so quick repeated degauss cycles isn't going to work, found that you needed to power off for a few minutes before a new degauss cycle would happen. I did distort the hell out of it though so took a few cycles to restore it to normal.