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The PVM-2730QM thread (H-STAT issue, colour bleed, convergence and more!)


buttersoft

Question

This thread started about a single issue, but is devolving into a more general thread about PVM-2730's, so I changed the title. These are basically the same as the KX27HG1 and KX27HG2 sets (powersupplies are swappable but may not be identical) along with the Japanese Profeel sets that look the same. They are close cousins of the US PVM-2530's and possibly the PVM-2550's. Different revisions have S-Video, and the US versions have a DB25 plug instead of SCART. The Japanese sets may use JP21. The service manual for the 2530 shows it to be a bit different inside, with a ton of tiny extra circuit boards and different layout. Still a lot of commonalities though, but it will pay to note these differences and check the schematics before touching anything.

 

Hi all,

 

I have a KX27HG1 (same thing as a PVM-2730) with a CRT fault. It powers up when cold, and then after twenty minutes, or even longer if it's freezing in the garage, there's a click (normally) and the screen shuts down. The picture folds in like the screen has been powered down, but the rest of the set still works - indicator lights, sound, etc. If I power-cycle, the tube powers up again for maybe a second, and then goes down. If I wait 10-20 seconds and power up again, the picture comes up for a few seconds, but the colours are bleeding sideways, particularly red. Then the CRT loses power again.

 

There's definitely a buzzing sound the whole time the picture is up, and it's not as stable as it should be at 240p, and the brightness flickers slightly. There's a click sometimes as it powers down that might be coming from the HVT/flyback, or might be something nearby.

 

Also, the "Screen" adjustment, on the neckboard of this set, doesn't seem to do a lot, mostly just messes with colour gain, but no huge brightness adjust or retrace lines appearing.

 

I just recapped the electroyltics in the power supply, and the same thing still happens. Any ideas where to go next? I've found replacement flybacks online, I think, but I'm not 100% on that being the problem.

 

Help greatly appreciated!

Edited by buttersoft
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So, i don't know why, but composite video inputs suddenly started working. Anyway, the red bleed is happening there as well. Below is a screenshot of the typical bleed on RGB - the more red there is on a line, the heavier the bleed. I've checked out the schematic, and the only caps in the red line after the jungle chip (composite video and RGB both go into the jungle chip, and the ~3V RGB to the neckboard comes out) are two 680pF ceramics on the red video line, and one 10nF polymer which is on the red gain. Nothing to ground or otherwise. I guess i should change those few caps, but if there's any further advice @NEO-GEO Man, I'm all ears :)

 

EDIT: Its two near-identical counterparts do this while warming up, and the red bleed swings back into line over about two seconds as the image grows to normal brightness. This set doesn't do that. The bleed is not there at first, and creeps into place over three or four seconds while the image comes up. It's probably creeping minutely sideways for about five seconds more.

 

Uardjqu.jpg

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So, i don't know why, but composite video inputs suddenly started working. Anyway, the red bleed is happening there as well. Below is a screenshot of the typical bleed on RGB - the more red there is on a line, the heavier the bleed. I've checked out the schematic, and the only caps in the red line after the jungle chip (composite video and RGB both go into the jungle chip, and the ~3V RGB to the neckboard comes out) are two 680pF ceramics on the red video line, and one 10nF polymer which is on the red gain. Nothing to ground or otherwise. I guess i should change those few caps, but if there's any further advice @NEO-GEO Man, I'm all ears :)

 

EDIT: Its two near-identical counterparts do this while warming up, and the red bleed swings back into line over about two seconds as the image grows to normal brightness. This set doesn't do that. The bleed is not there at first, and creeps into place over three or four seconds while the image comes up. It's probably creeping minutely sideways for about five seconds more.

 

[ATTACH=CONFIG]104651[/ATTACH]

Itll only be electrolytic caps if it is at all.

 

What is there prior to the jungle IC?

 

Generally you get that bleed because the colour is over-driven or there is faulty electrolytics somewhere. If you turn contrast right down does the bleed go away?

 

What is on the neck board in terms of capacitors?

 

- - - Updated - - -

 

I probably need to see the whole video circuit from entry to neckboard to know what could influence this.

 

Ive seen numerous NECs do this, it was always capacitors, and lowering the red drive made it go away, lowering contrast did the same thing. It was always on red, but ive seen it on green as well to a lesser degree.

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Yeah I was thinking electrolytics as well, but there aren't any in the red line after the Jungle IC. There are certainly a few on the neckboard though, so i'll give those a look. The jungle IC basically feeds straight to the neckboard, so I presume you'd be thinking the problem was on there?

 

From memory, yes, turning down the screen/sub-bright/brightness options will reduce the bleed. Haven't really tried the red bias yet but I reckon it'll do the same. The problem is that to bring the red into line, the overall brightness has to go lower than acceptable. The set is over 30 years old now.

 

Schematic linked, the neckboard is on pdf page 113 (parts list on p135). The rest of the circuit is back/above, SCART inputs starting on pdf page 101. The ancient scan has pages out of order, but the circuit is still huge. It's the only version of the service menu available, and my model is slightly different, not having the S-Video capability.

 

If this is starting to feel like too much work, I totally understand :)

 

http://freeservicemanuals.info/servicemanuals/download/Sony/pvm-2730qm.pdf

 

EDIT: There are some electros on the neckboard related to brightness, from what I can see.

Edited by buttersoft
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Yeah I was thinking electrolytics as well, but there aren't any in the red line after the Jungle IC. There are certainly a few on the neckboard though, so i'll give those a look. The jungle IC basically feeds straight to the neckboard, so I presume you'd be thinking the problem was on there?

 

From memory, yes, turning down the screen/sub-bright/brightness options will reduce the bleed. Haven't really tried the red bias yet but I reckon it'll do the same. The problem is that to bring the red into line, the overall brightness has to go lower than acceptable. The set is over 30 years old now.

 

Schematic linked, the neckboard is on pdf page 113 (parts list on p135). The rest of the circuit is back/above, SCART inputs starting on pdf page 101. The ancient scan has pages out of order, but the circuit is still huge. It's the only version of the service menu available, and my model is slightly different, not having the S-Video capability.

 

If this is starting to feel like too much work, I totally understand :)

 

http://freeservicemanuals.info/servicemanuals/download/Sony/pvm-2730qm.pdf

 

EDIT: There are some electros on the neckboard related to brightness, from what I can see.

 

Yeah itll likely be those on the neckboard. It wont go direct from IC to tube without some other circuitry in the path, and the fact lowering contrast corrects it leads me to believe itll be capacitors.

 

Can you post a pic of the neckboard?

 

- - - Updated - - -

 

If it was all 3 colours doing something like this, id be looking for a 10uF 250v electrolytic on the neckboard, even still id be looking at that one anyway.

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The only cap on the neckboard anywhere near those specs is arrowed red - #704 22uF/250V. And the one in the top right corner, I guess, #703 4.7uF/100V. The first one seems to be the go.

 

Apologies for size of image, but any smaller and it'll be illegible.

 

D5bawlA.png

 

L-click, then R-click, then view image, then L-click to get full size...

g7FebSW.png

 

EDIT: I'm happy to just redo all the electros on the neckboard though, it's not that much work. Would be helpful to diagnose where the problem is though :)

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The only cap on the neckboard anywhere near those specs is arrowed red - #704 22uF/250V. And the one in the top right corner, I guess, #703 4.7uF/100V. The first one seems to be the go.

 

Apologies for size of image, but any smaller and it'll be illegible.

 

[ATTACH=CONFIG]104792[/ATTACH]

 

L-click, then R-click, then view image, then L-click to get full size...

[ATTACH=CONFIG]104793[/ATTACH]

 

EDIT: I'm happy to just redo all the electros on the neckboard though, it's not that much work. Would be helpful to diagnose where the problem is though :)

 

Yeah thatll be it, but may as well do them all. Dont use Jaycar rubbish.

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Roger that

 

Recapping the electros on the neckboard has not had any effect, sadly. The bleed is still just as bad. I might move on to the polymers next. I still doubt it's a transistor issue, as the bleed isn't just happening on red.

 

On a positive note, I recapped the electros on the nearby D2 convergence board because hey, why not while you're there, and it fixed the dynamic convergence issue I was having. I didn't even have to adjust anything, just set the pots to neutral before plugging back in, and then a small H-Stat adjust to bring everything into line. I think I'll do the same to the other two sets.

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Recapping the electros on the neckboard has not had any effect, sadly. The bleed is still just as bad. I might move on to the polymers next. I still doubt it's a transistor issue, as the bleed isn't just happening on red.

 

On a positive note, I recapped the electros on the nearby D2 convergence board because hey, why not while you're there, and it fixed the dynamic convergence issue I was having. I didn't even have to adjust anything, just set the pots to neutral before plugging back in, and then a small H-Stat adjust to bring everything into line. I think I'll do the same to the other two sets.

 

Its extremely unlikely to be polymer caps.

 

How worn is the tube? If you have to drive it hard you may get bleed as a result, but the red should be the last to be affected.

 

Can you move the chassis boards over to another tube? It will have to be the same tube type and same yoke.

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Hah, it's a 25" PVM Trinitron tube; so no, next to zero chance of getting a replacement save from the 2 working ones I have. I'm not 100% sure these tubes were used anywhere but the PVM/Profeel line. There's not just a yoke there's a full neck assembly. And that split anode for HV feedback, which I think all Trinitrons have.

 

The tube isn't being driven too hard, the bleed is *just* there with everything on minimum. Still I think recapping the neckboard has actually brightened things up a smidgeon. I might investigate functionality.

 

I'm probably going to give the polymers a go to see what happens.

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Hah, it's a 25" PVM Trinitron tube; so no, next to zero chance of getting a replacement save from the 2 working ones I have. I'm not 100% sure these tubes were used anywhere but the PVM/Profeel line. There's not just a yoke there's a full neck assembly. And that split anode for HV feedback, which I think all Trinitrons have.

 

The tube isn't being driven too hard, the bleed is *just* there with everything on minimum. Still I think recapping the neckboard has actually brightened things up a smidgeon. I might investigate functionality.

 

I'm probably going to give the polymers a go to see what happens.

 

No what i mean is swap the boards between your sets, this will tell us if it is the tube or the boards. Youll certainly never find another one, and yes those tubes are specific to the PVM series, the BVM series had different tubes and domestic grade sets had different tubes as well ( the PVM and BVM tubes are probably compatable though, not that it matters at this point )

 

Dont pull the yoke off.

 

If the boards move into another set and the issue remains, leave the main board in and swap out all the other boards 1 at a time between the known working set to see where the issue is. Not sure how many boards can be swapped out between sets, make sure theyre the same board type before swapping though.

 

- - - Updated - - -

 

Even though you say the bleed remains on minimum setting, cant rule out that the G2 is not set correctly, or that a heavily worn electron gun assembly is sending the G2 up high. This set will almost certainly have AKB, which will set the G2 where ever it thinks it needs to be, but for this to operate correctly it must be callibrated correctly.

 

There is a few things this could still be because these are pretty complex sets for their age.

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Yes, they are complex. Sony apparently renamed AKB as ABG, for their own reasons as usual. I'll look into it. Would a set from the very late 80's have it though?

 

Sadly the sets are not perfectly identical. 7 of the 13 PCBs are interchangeable - convergence, power, sub-power, flyback, rear control board, and front control boards A & B. The other 5 or 6 are mostly the same but with little differences - one set does S-Video, another doesn't have a particular minor geometry adjustment (or the header and cable for it). I'll have to examine them. That's if i haven't forgotten any boards :) Not counting the audio board because I was just going to leave it alone, of course.

 

Appreciate the help, and as usual don't wait around - it'll be months before i gear up and actually do something :)

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Yes, they are complex. Sony apparently renamed AKB as ABG, for their own reasons as usual. I'll look into it. Would a set from the very late 80's have it though?

 

Sadly the sets are not perfectly identical. 7 of the 13 PCBs are interchangeable - convergence, power, sub-power, flyback, rear control board, and front control boards A & B. The other 5 or 6 are mostly the same but with little differences - one set does S-Video, another doesn't have a particular minor geometry adjustment (or the header and cable for it). I'll have to examine them. That's if i haven't forgotten any boards :) Not counting the audio board because I was just going to leave it alone, of course.

 

Appreciate the help, and as usual don't wait around - it'll be months before i gear up and actually do something :)

 

Its quite likely a set from the 80s that is in the professional grade would have wear compensation yes, NEC had it on their CRT projectors right from the start.

 

AKB was the name NEC gave it i think, every brand has their own name for it.

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Yes, they are complex. Sony apparently renamed AKB as ABG, for their own reasons as usual. I'll look into it. Would a set from the very late 80's have it though?

 

Sadly the sets are not perfectly identical. 7 of the 13 PCBs are interchangeable - convergence, power, sub-power, flyback, rear control board, and front control boards A & B. The other 5 or 6 are mostly the same but with little differences - one set does S-Video, another doesn't have a particular minor geometry adjustment (or the header and cable for it). I'll have to examine them. That's if i haven't forgotten any boards :) Not counting the audio board because I was just going to leave it alone, of course.

 

Appreciate the help, and as usual don't wait around - it'll be months before i gear up and actually do something :)

 

Been a while, but i got a bit more info for you. Apparently the transistors can cause this so might be worth replacing those and see how it goes. Sounds good enough in theory.

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Been a while, but i got a bit more info for you. Apparently the transistors can cause this so might be worth replacing those and see how it goes. Sounds good enough in theory.

 

Cheers! The neckboard transistors, I imagine we're talking about? I'll have a look - hopefully they're discrete units, but i reckon Sony will have used some proprietary all-in-one solid state nightmare :: Let's find out.

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Hmm. When the set powers on, the yellowish red bleed is godawful, and as the picture comes up to full brightness/colour over the first 2-3 seconds, the bleed swings mostly back into line. This isn't the only one of these sets that's doing it, but the bleed doesn't quite go away completely on this one.

 

Given that 2-3 seconds adjustment, is this going to be the transistors? I'm not saying it isn't, just trying to work things through before i spend more money :)

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Hmm. When the set powers on, the yellowish red bleed is godawful, and as the picture comes up to full brightness/colour over the first 2-3 seconds, the bleed swings mostly back into line. This isn't the only one of these sets that's doing it, but the bleed doesn't quite go away completely on this one.

 

Given that 2-3 seconds adjustment, is this going to be the transistors? I'm not saying it isn't, just trying to work things through before i spend more money :)

 

Possibly, they might be buggered when theyre cold, and check the resistors around that area too

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Possibly, they might be buggered when theyre cold, and check the resistors around that area too

 

So, from the schematic - any idea which transistors? I was thinking the drive transistors to begin with? And the littler one just below them on each line.

 

[ATTACH=CONFIG]104793[/ATTACH]

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I've been thinking about the colour-bleed problem on and off, and the fact it's really a whole picture bleed problem and not limited to one or two colours. If it was transistor-related, all three colours going wrong is not likely. Which could leave any single transistor in the bias circuit, if i'm even naming that right, like Q710 or Q712. (Ignore the red arrow i drew earlier.) EDIT: No, those are part of the V-blank AKB feedback, from the looks of things. So probably not related at all.

 

[ATTACH=CONFIG]116428[/ATTACH]

 

However, general consensus on the google seems to point to a worn CRT. Rejuvenation being the answer. It wouldn't surprise me, these sets were probably sitting around for 15 years before i got to them.

 

http://www.thegleam.com/ke5fx/crt/sencrt.pdf

 

"I can't adjust the color on this monitor. It looks real dim. If I try to turn up the pots on the neck board, the picture just smears to the right. If I try to turn up the brightness on the remote adjustments board, the picture smears to the right. If I try to turn up the contrast, the picture smears to the right. I have the screen pot turned up as high as it can go without seeing raster and vertical retrace lines washing over the whole screen."

Then, as if a sudden revelation has come over the caller, he perks up and queries

"Hey! Could it be a bad picture tube?"

The answer, of course, is "Yes."

 

Thoughts, @NEO-GEO Man? Any tips on rejuvenating a Trinitron with it's messed-up pinout, if it does come to that?

 

EDIT: Also watching this fiend and wondering, because i don't have access to a high-bias rejuvenator, and i think i need one to attempt any legit rejuv. This would have to be last-ditch, as the guy himself notes.

g7FebSW.png

Edited by buttersoft
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I've been thinking about the colour-bleed problem on and off, and the fact it's really a whole picture bleed problem and not limited to one or two colours. If it was transistor-related, all three colours going wrong is not likely. Which could leave any single transistor in the bias circuit, if i'm even naming that right, like Q710 or Q712. (Ignore the red arrow i drew earlier.) EDIT: No, those are part of the V-blank AKB feedback, from the looks of things. So probably not related at all.

 

[ATTACH=CONFIG]116428[/ATTACH]

 

However, general consensus on the google seems to point to a worn CRT. Rejuvenation being the answer. It wouldn't surprise me, these sets were probably sitting around for 15 years before i got to them.

 

http://www.thegleam.com/ke5fx/crt/sencrt.pdf

 

 

 

Thoughts, @NEO-GEO Man? Any tips on rejuvenating a Trinitron with it's messed-up pinout, if it does come to that?

 

EDIT: Also watching this fiend and wondering, because i don't have access to a high-bias rejuvenator, and i think i need one to attempt any legit rejuv. This would have to be last-ditch, as the guy himself notes.

 

Ive not actually ever done a rejuvenation before, so im not sure just how effective it may be on that issue.

 

Im more of a CRT projector guy, and in those situations i generally throw the reds away if they go faulty because theyre so common, but greens and blues id consider trying if they were not too worn.

 

Ive seen a lot of Panasonic P19LUG tubes have contamination issues which can be fixed SOMETIMES with a rejuvenator, but not always.

 

I had a green projector tube do what youre describing, and it was the fact it had a massive 23,500 hours on it and the gun was simply rooted, meaning it had to be driven very hard to get the brightness needed.

 

The fact the Sony will likely have some form of AKB or auto brightness leveling control will possibly add to that issue, if indeed the guns are worn beyong their service life.

 

Id expect something more like 80,000 hours out of a direct view set before the guns become unservicable.

 

Sorry for slow reply on this, i have been through a bit of a tough time lately, my partner was recently diagnosed with breast cancer and has been quite sick.

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No no, no need to apologise, life comes first. I hope things work out.

 

I've heard, from Joey among others, that rejuvenation works best on tubes that look funny after sitting around for 20 years unused. In fact i've seen how well it can work in those instances. I'd guess at these sets sitting around for about 15 years without being switched on, so hoping i might have a similar situation.

 

In other news, i saw a projector setup the other day that made me cry. 1080p at 48Hz, for film, though capable of much more. So goddamn colourful, so rich. I get why you're into it.

 

PM sent as well.

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No no, no need to apologise, life comes first. I hope things work out.

 

I've heard, from Joey among others, that rejuvenation works best on tubes that look funny after sitting around for 20 years unused. In fact i've seen how well it can work in those instances. I'd guess at these sets sitting around for about 15 years without being switched on, so hoping i might have a similar situation.

 

In other news, i saw a projector setup the other day that made me cry. 1080p at 48Hz, for film, though capable of much more. So goddamn colourful, so rich. I get why you're into it.

 

PM sent as well.

 

Yeah mate i have run 1080p and also 2560x1440p at 48Hz on my Barco CRT projector and it was so sharp and clear, but i found the flicker in some scenes a bit much for my liking, so i usually run 60Hz or 72Hz for better smoothness. With the OPPO bluray player the conversion from 24p to 60 is very very good.

 

Im yet to see a digital projector i could live with as far as black level goes, theyre just not there yet, where as CRT can go totally black in one area and still full white right near it, and being liquid coupled there is almost no light spill, colour filtered c-elements give very accurate primary colours, so if set up well, a top analog projector can still flog a digital at 1920x1080p for film material. Once UHD becomes more common i wont be able to resolve that on the CRT, but i can do 3840x2160i without a problem, it requires some pretty tricky mechanical setup and the right timings etc to give a good result though.

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