Ollie's PVM Giveaway Repair Thread

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.

eddhorse · 15-04-2022 9:32pm

May get the degaussing wand out

80s Synth Pop · 17-04-2022 8:53am

https://www.boards.ie/discussion/comment/118932665#Comment_118932665

RIP eddhorse

eddhorse · 19-04-2022 1:28pm

Finally took this apart to clean and inspect.

Looks like a cap C406 issue and resistor R457 issue also.

eddhorse · 19-04-2022 3:31pm

PTC removed, second hand desoldering gun FTW. Interesting to see the PTC as it disintegrated.

Inviere · 19-04-2022 4:28pm

Safe to say that's a right-off there @eddhorse

eddhorse · 19-04-2022 4:44pm

https://www.boards.ie/discussion/comment/118947044#Comment_118947044

Bit of hot glue, be grand

KeRbDoG · 02-05-2022 11:25pm

OK, so had time to try the RGB mod. Mounted BNC connectors on the input panel as I found a SCART->BNC cable I had for another LCD BVM.

Seems to work well but I've noticed that colours fade slightly over a few minutes, might be something to tweak the voltage divider on the inputs. I didn't have time to check this with a normal composite input.

The Last Bandit · 03-05-2022 9:14am

Good stuff :)

Ya try with the composite on the other channel and see if the picture fades as well, could be problems with the RGB drivers. Throw on a RGB test screen and see if all the colours fade or just one or two.

The RGB mod does override the default brightness settings for the RGB channel so could be also be an issue.

Inviere · 03-05-2022 10:54am

Still waiting on the parts from Ali....sigh,some day....

KeRbDoG · 03-05-2022 4:05pm

https://www.boards.ie/discussion/comment/119008502#Comment_119008502

Cool, thanks for the tip - will do more testing when I get a chance.

Another interesting finding was that a NeoGeo AES & RGB modded Sharp Disk system didn't display anything on RGB. Genesis/MegaDrive worked just fine. Didn't test more consoles. More work needed

eddhorse · 04-05-2022 10:44am

Anyone got links to best place to get Arduino for the mod ?

https://immerhax.com/?p=558

KeRbDoG · 04-05-2022 3:16pm

https://www.boards.ie/discussion/comment/119013652#Comment_119013652

I ordered up via eBay as I knew I had lots of time on my hands with AliExpress and the PTCs :D

eddhorse · 11-05-2022 5:28pm

Well mine is up and running and staying on. Hadn't anything connected to it, but don't think this is correct when you press menu. Didn't leave it on this for long.

Inviere · 11-05-2022 6:10pm

https://www.boards.ie/discussion/comment/119047411#Comment_119047411

Hmm, horizontal/vertical collapse?

eddhorse · 11-05-2022 6:22pm

Yep looks like it, more fun.

Least its staying on right?

Wait I just remembered I didn't plug in the yoke wires lol, may go back out and check.

Senior moment

eddhorse · 11-05-2022 6:33pm

Thats better, it should be yellow right?

Inviere · 11-05-2022 7:22pm

https://www.boards.ie/discussion/comment/119047668#Comment_119047668

Unknown Ed, I'm STILL waiting on my PTC's. Eta is June 1st but no sign of them even being in the country yet, so who knows. The image looks right anyway, and nice senior moment fix 👍😉

The Last Bandit · 11-05-2022 9:04pm

Yep yellow is correct colour for the menu alright.

@inviere pm me your address and I'll send you one of my spares

eddhorse · 11-05-2022 10:57pm

I also have PTC spares now too.

Who wants one?

Inviere · 12-05-2022 7:27am

@The Last Bandit & @eddhorse absolute gents, thanks so much. When mine arrive I'll happily replace yours or donate to another needy soul 👍

Inviere · 28-05-2022 2:54pm

Another one rises from its grave. Thanks to @BGOllie @eddhorse and @The Last Bandit for the parts and help.

The second one however, does try to start up but immediately blows its fuse. This is with the ptc replaced, and new fuses each time. Something is obviously shorted to ground somewhere, where on earth do you even begin to try to find out where the problem is?

BGOllie · 28-05-2022 3:39pm

wonderful work lads . happy the didn't end up in the skip

Inviere · 28-05-2022 5:15pm

Brain flash, I'll swap the voltage regulator from the working one to the one with issues and see if that's the problem. Reread the thread again and there's some ideas early on in it. Prob won't get to it until nearer next weekend tho

Inviere · 30-05-2022 7:48am

https://www.boards.ie/discussion/comment/118880797#Comment_118880797

@KeRbDoG did you ever get to the bottom of the monitor that turns on briefly and turns back off? Same symptoms as one of mine here.

@eddhorse the cap and resistor pic you showed above, what were the symptoms of that screen not working?

KeRbDoG · 30-05-2022 11:13pm

@Inviere I haven't had time to work on the monitors since the RGB mod of one of them. Will be a bit of a needle in a haystack whenever I do though

eddhorse · 31-05-2022 12:02am

Tested the cap and it was actually fine, after I bought those mylar ones and all.

The resistor at R457 was toast though.

Inviere · 31-05-2022 5:26am

https://www.boards.ie/discussion/comment/119137658#Comment_119137658

Cheers Ed, and what was the symptom on that, was the screen dead or powering off etc?

eddhorse · 31-05-2022 7:31am

Well I just gave the board a look over before the PTC replacement.

You can see it in the earlier pic being toasted.

So more of an obvious visual thing than device issue.

Inviere · 07-06-2022 12:58pm

Swapped over the voltage regulator, and some of the power area caps this morning. No joy on the 2nd monitor, just shuts off as soon as it powers up. You could spend hours swapping parts, without the proper knowledge of how to diagnose this. Plus its also possible a chain of components has been taken out due to the failure of one other component, so who the heck knows

Inviere · 07-06-2022 4:13pm

https://www.boards.ie/discussion/comment/119168941#Comment_119168941

Oh while I had both monitors open, I swapped over the main daughter/input board too, just as a final roll of the dice. Same result, so nothing on that board is causing the issue, predictably.

Inviere · 25-06-2022 12:56pm

I tried swapping some more components over from the working to non working one today, still no joy. Tested some caps, swapped some caps, swapped over the Vertical IC, reflowed some odd looking joints....I can't for the life of me get the second one to power up. To add insult to that, the one that was working, now doesn't display any image when powered up...and I genuinely haven't got the time to swap the Vertical IC back over to the working one.

So on that note, I'm out. I've too much in the queue waiting to be worked on, and I'll pass these on to someone else. x2 of them, one powers up with no image, one powers up briefly and shuts down then a second later. I'd say the no-image one just needs its Vertical IC swapped back over from the other one, and it should be fine (there's pics of it working earlier in this thread).

So, does anyone from here want them for spares for the ones you already have? Or to get them working again? I'm asking here as opposed to the Marketplace because I want them kept in the 'circle of trust', and NOT to go to someone who will flip them. If nobody here wants them, I'll stick an ad up then, free obviously.

Inviere · 26-06-2022 8:37am

Ad up - https://www.boards.ie/discussion/2058251838/free-x2-jvc-pvm-monitors/p1?new=1

Inviere · 27-06-2022 11:07am

https://www.boards.ie/discussion/comment/119247876#Comment_119247876

Cancel this. I hate giving up on anything, so went back to this today as I'd a small window of time. Good lord I must have been goggle-eyed from looking at pcb's on Saturday and swapping bits over. I seen that I had indeed swapped the Vertical IC over.....but never soldered it in! Brain fade at its finest! That could have been a real handy fix if someone had of grabbed these 🙃

Inviere · 27-06-2022 11:14am

So back in the game. I'd LOVE to get the other one working, but it exhibits the same fault that @KeRbDoG has mentioned on one of his...turns on, but after a second or so it shuts off and stays dead for a few minutes until something discharges. I've tried swapping the main voltage regulator, the vertical IC, several main caps, the PTC, and the large PTC resistor. No matter what, it exhibits the same behaviour. There's obviously something gone funky somewhere, but tbh, I'm not exactly in my comfort zone working on these given the lethal voltages, so couple that with limited knowledge of crt operation/circuitry, I feel like I'm shooting in the dark hoping whatever I swap next will be the thing that's causing the problem.

@BGOllie did mention potential issues in the x-ray protection area too, so maybe that's where the fault lies? The one thing that makes me reluctant to keep swapping parts from the working one over, is that of a possible fault-chain - where something faulty can take out what were working parts further down the circuit.

dav09 · 27-06-2022 11:16am

Have to take a look at mine soon, ordered some parts recently but haven't arrived yet. Have two and if I can fix both have promised to give one to a buddy for free as he's always wanted a PVM. If I cant fix them I'll list them here again for free.

o1s1n · 27-06-2022 12:21pm

https://www.boards.ie/discussion/comment/119256114#Comment_119256114

That's absolutely gas! Well done on getting it sorted, been quite the process to watch.

Ollie's PVM Giveaway Repair Thread

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