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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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I think it might be too predictable for a cold joint? It happens like clockwork. At the same ambient temperature the set'll take exactly the same time until it cuts out. And if you leave it for less than about 2-3 minutes after that, it cuts out pretty much immediately on restart. I would have thought a cold joint might produce slightly random behaviour? Or at least cool down quicker?

 

I'm definitely going to give it a look though, thanks. I did notice @Rat talking about his in the pro-monitor thread, so hopefully he or someone else can shed more light.

 

EDIT: It is obviously making a louder buzzing noise than expected though, and the screen is flickering, so mb. I dunno, I'll try to give it a look.

Edited by buttersoft
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This joint looks fine, right? lol.

 

dHhcviS.png

 

It's a 3-pole thermistor, and there isn't much, if any burn around it, mostly just old flux. But the joint has obviously gone bad and probably overheated. Anyone know much about thermistors? How can i test it? Should I just replace it? I can find the part for $10 + postage on an Aus site, of all things.

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This joint looks fine, right? lol.

 

[ATTACH=CONFIG]94508[/ATTACH]

 

It's a 3-pole thermistor, and there isn't much, if any burn around it, mostly just old flux. But the joint has obviously gone bad and probably overheated. Anyone know much about thermistors? How can i test it? Should I just replace it? I can find the part for $10 + postage on an Aus site, of all things.

 

That is probably just for the degaussing coil. You are really running blind with this and I wish you all the best repairing it.

 

I would go over the powers supply and horizontal/flyback areas for dry joints touching up anything that looks dodgy.

 

After that if it still didn't behave, if it was mine, I would bin it I'm afraid.

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That is probably just for the degaussing coil.

 

Well spotted, that man. On further examination it is for the degaussing circuit. There are a few other joints on the power supply I'm not 100% happy with the look of, but nothing else anywhere near as bad. I have found replacement flybacks online, and possibly something that will do for the HVR block because i'm not sure i can separate the two without destroying something.

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So after working at it all day, swapping parts out with the other, almost-identical unit I have, I've isolated the problem with a high degree of certainty to the Flyback or the HVR block. When it first powers on, the screen is tinted red, and after it craps out and I wait 30 seconds it comes back up for a few seconds with the red bleeding all over the shop horizontally, very slowly drifting back into position - for about 5 seconds before it cuts out again.

 

Does that sound like the flyback? I can get a flyback from a few places. The HVR block might prove tricky. I still need to test the V-def board that's feeding the yoke, but I imagine if that failed I'd be getting vertical collapse? Or no picture at all?

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Dump it

 

Not on your life!

1. PVM's are getting to be valuable.

2. I have identical units. This unit has a single problem, and at worst I can use it for parts.

3. With careful testing I've narrowed the problem down to the HVR or the Flyback.

 

Now I need to beg borrow or steal a high-voltage probe to decide if it's one or the other, because while the flyback is about $50 the best I can do for the HVR is a similar part that *should* work and will cost $100. Or I could just bypass the x-ray/overvoltage protection (lol, cos that would be really smart) ;)

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Not on your life!

1. PVM's are getting to be valuable.

2. I have identical units. This unit has a single problem, and at worst I can use it for parts.

3. With careful testing I've narrowed the problem down to the HVR or the Flyback.

 

Now I need to beg borrow or steal a high-voltage probe to decide if it's one or the other, because while the flyback is about $50 the best I can do for the HVR is a similar part that *should* work and will cost $100. Or I could just bypass the x-ray/overvoltage protection (lol, cos that would be really smart) ;)

 

Doesnt sound like HV to me, that wont cause streaking or banding like that.

 

Id say take a real good look at the neck board, and follow that up with the video amps.

 

The HV will shut down to protect the set from damage in a lot of cases, that is pretty normal really.

 

The fact its all tinted towards red leads me to think red is high, or green and blue are low, and this could be anywhere, but is very unlikely to be in the SMPS section.

 

If the set suffers a deflection failure of sorts this could result in protection circuitry shutting off HV to prevent spot burn on the CRT, so what id do is go over any solder joints that are in the video amp sections, as well as the deflection section, then replace all capacitors on the neckboard, reflow the CRT socket solder joints, and any transistors on the neckboard.

 

I dont reckon its the HV tansformer from what you describe, lowered HV will result in the picture growing in size, arcing HV will show distortion on screen but generally normal colours, so unless im mis-interpreting your symptoms id say aim for other areas first.

 

When you say careful testing, what conclusive evidence do you have to lock the HV transformer in as the offending part?

 

Dont disable anything. The protection circuits are there for a reason, and that is to prevent further set damage in the event of component failure.

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lowered HV will result in the picture growing in size, arcing HV will show distortion on screen but generally normal colours, so unless im mis-interpreting your symptoms id say aim for other areas first.

HV is not arcing, and PVM's have legendarily good bloom protection, which I would imagine extends to picture size overall. That said, I'm going to have a very good look at picture size when I power-cycle.

 

I may not have done a very good job of describing the symptoms, but essentially the set works normally until it hits that cutoff, and it does so like clockwork, dependent on ambient temp. Power cycling then produces the interesting issues. The picture seems the right size, but i'll check, and there's no banding, just red bleeding heavily right, over more area than it should cover, slowly correcting itself but before it gets there the set shuts the picture down again. If I leave it off for five minutes, I'll get a full minute or so of normal picture before the fault kicks in and the picture drops. Leave it until next day when it starts cold, and you can just about set your watch by how long it takes to power the tube down - again, dependent on ambient temperature.

 

I've already swapped out the main power supply, and the H- & V-deflection boards (The H-board also does over-voltage protection and regulates the power to the flyback). Added to which, if I had to pick one or the other, I'd say it wasn't the flyback ;)

 

When you say careful testing, what conclusive evidence do you have to lock the HV transformer in as the offending part?

... Which is why I blamed the flyback *and/or* the HVR. I did fair amount of googling, finding out it's not an uncommon problem as far as these sets go. The blocks tend to cook themselves while the voltage dividers inside slowly degrade. Sometimes failure is catastrophic (arcing), sometimes not, as I think has happened in my case. I can't get anything to arc even when poking under and around the block and cap with my discharge lead.

 

This has been followed by a fair amount of multimeter testing on my part. The flyback is being fed a a constant voltage, and it's the correct voltage. Other important voltage settings look good too. The HVR/H.stat/HV-resistor-assembly's low-voltage output lines, however, are drifting while the set is on. Or one of them is; I need to test a bit more. When the difference between them slips below ~3.3V, the picture collapses. (That difference starts at about 12V). These two lines form the direct inputs for the HV protection IC. Bridging those lines with my voltmeter acts as a slow short, and hastens the set cutting out by a factor of about 10.

 

I have not tested the HV directly. But. None of the bad stuff above is true for the identical set I have, with or without the parts swapped around. With this second set the difference between the HVR-overvoltage lines is constant at 4.66V very shortly after power-on. Applying my meter does not cause any interruption or slow short as above.

 

This could all be a problem with the flyback, I realise, and for that I can at least acquire a compatible part. The levels on the overvoltage lines, the way they start really high and then drop slowly but constantly. There was a little flicker in the picture too, but that seems to have gone away. I guess I'm trying to figure out what's actually wrong before going further slash spending money.

 

Any help or ideas would be gratefully appreciated, @NEO-GEO Man. If with this new information you still think it's the neckboard I can just swap that over too :) I'd love to find a replacement HVR in case I need one (Sony part # 1-230-712-21 or 22 or better yet 23) or to even be able to figure out what's inside the damn thing because it's like a 12 x 8 x 3 rectangular dish of heavy lucite potted in rock-solid red epoxy. I'm not even sure how to disconnect the leads from it, they seemed to be fixed. Hence my wanting to buy both it and the flyback.

 

[in fact you've given me a couple of ideas... The flyback for this set doesn't supply anything but the HVR - there's only one lead coming out of it, and it only has the one pot (focus, obv.). I should at least make sure that when the set cuts out, those overvoltage lines go to zero. I'm sure I watched that happen a few times, but now can't remember. The protection circuit should just cut the power to the flyback anyway. But it's 5 degrees in my garage atm, no joke, and I want my headcold to depart. I could even try freezing the HV block with canned air or something and seeing if that does much, but I don't like the sound of that.]

 

Pic is the HVR assembly. Not the best angle. Red lead comes from the flyback, white lead goes to anode cap as you can see. The overvoltage lines are grey and come out the back on the right. The two lines connected to the RFI shield are ground lines and also screen the overvoltage lines as the cable passes over the H-def board. The knob on top adjusts the static convergence. I think this setup is quite similar to a lot of Sony aperture-grille sets, and thus I may be able to use the HVR assembly from another 27" Trinitron even if it's not identical.

 

WP_20160520_17_24_55_Pro.jpg

 

Dont disable anything. The protection circuits are there for a reason, and that is to prevent further set damage in the event of component failure.

That part was a bad joke. I might do it to test things -briefly- but only to help diagnose the problem.

Edited by buttersoft
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The HVR as you call it has a number of high voltage capacitors and diodes in it, ive not seen a Sony unit fail, but seen loads of them fail in Barco projectors. Generally speaking the capacitors were not a high enough rating and begin to arc between each other, making an audible squealing noise and a bit of picture noise visible on screen. Cant say for sure if youre likely to see and hear the same with a Sony.

 

If anything in the HV side fails, it should not cause smeared colours like youre saying occurs.

 

To remove those HV cables, push inwards and twist. They look identical to those Sony used on their CRT projectors. They should come out the same, and if so, you could try swapping that part for a known good one.

 

Id swap the neck board first of all, because it takes a couple minutes. The video amps may be on the neck board, but if not then look to see where they are next.

 

- - - Updated - - -

 

DO NOT adjust that pot on the red box until you are CERTAIN you know what it does and what is required to adjust it.

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Thanks for taking the time. I'll swap a few more components and see. I think the first-stage RGB amps are going to be on the B board. With those overvoltage lines drifting I don't reckon the other bits are the problem, but as you say, it's worth a shot.

 

EDIT: the picture was getting a little flicker in it, if that counts as noise? Mostly toward the bottom of the frame.

 

DO NOT adjust that pot on the red box until you are CERTAIN you know what it does and what is required to adjust it.

 

I was a bit leery at first, but it's used for static convergence, believe it or not :) The service manual lists it as one of the adjustments to make at certain times when tuning the set. 90% of the adjustments are pots in one place, and then there's this thing. For extreme adjustments you can still use the purity rings though. I spent a couple of hours perfecting the other set.

 

This is what happens when you turn it one way... on the working set at least. I should probably see what happens on the broken set, but i think it's the same IIRC. As i said, I can't get it to arc, so it's probably safe. But I might re-adjust it with a long piece of plastic nonetheless.

 

WP_20160520_17_13_47_Pro.jpg

Edited by buttersoft
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Thanks for the tip on getting those leads out, Neo Geo Man. I haven't done it yet, but the red lead moved handily, so it should come out when I have more time and the fricking garage warms up. If i can get it out and get the anode cap off I can probably swap the HVR blocks around, and see what gives.

 

Anyone have any tips about getting a trinitron anode cap off? They look different under the rubber - do they come off in some special way?

 

I haven't yet swapped the neckboards over, but i did measure the RGB lines as they hit the neckboard on the problem set, and they're stable on a static image, and all about the same 3.5V level.

 

Meanwhile the overvoltage lines still drift. I have figured out that I could bridge the two with a set of resistors, MB about 40M from one to the other and then 60M from the red one to ground, and still have the HV protection circuit operate. But it wouldn't be anywhere near as sensitive or quick to respond, so i'd need to test things and see what values I can get away with and decide if I'm happy with that. I almost certainly won't be, I realise, because I won't be able to prove the HV won't drift too far, or more likely that the block won't degrade further and start sparking into the RFI shield.

 

I'm not quite sure how to swap the neckboard over. It does actually have a lead going to the flyback (I must have missed it before in the dark) and the socket is attached to the board. Do those normally detach or desolder easily? It's like one that would have a red and a black lead in the white block attached to one side of the CRT socket, but this one only has a black lead that I'm pretty sure isn't going to be ground.

 

First things first, ima try and swap the HVR block over in the next few days :)

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Something you should be aware of is that 'most' professional service technicians hated Sony monitors above all else and with VERY good reason.

 

They were usually over complicated, exceptionally difficult to pull apart and even more difficult to fault find.

 

I actually can't recall when I ever repaired one to my satisfaction and at a profit.

 

It would pay to remember that.

 

I certainly admire your persistence but it really belongs here............

 

bondi-rubbish-tip.jpg

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Something you should be aware of is that 'most' professional service technicians hated Sony monitors above all else and with VERY good reason.

 

They were usually over complicated, exceptionally difficult to pull apart and even more difficult to fault find.

 

I actually can't recall when I ever repaired one to my satisfaction and at a profit.

 

It would pay to remember that.

 

I certainly admire your persistence but it really belongs here............

 

[ATTACH=CONFIG]95102[/ATTACH]

I tend to agree with it all up to that last bit.

 

But yeah, i never went past the 1001-QM before i moved to the considerably more reliable NECs. There were some Sony products that they shouldve supported better but did not. The G90 was one, suffered a reasonably terminal failure on the YA board.

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Alrighty then, I've swapped the HVR block in the faulty set with the one in the working set, and vice versa. Knowing how to disconnect the flyback lead was a huge help, and struggling through the anode cap removal (the hieroglyphs for which on the back of the rubber cup now make total sense) wasn't toooo painful, though it covered me in ancient black dielectric grease.

 

Now the previously working set has the same fault, same drift in the overvoltage lines, right down to the massive red smear when powering back up. (I've figured out how to cheat the overvoltage lines just slightly for testing, though i think it only works due to the fault. It does work the same way on both sets though.)

 

The faulty set now works perfectly, and the measurement across the overvoltage lines, when inputting the set with the same static image from the same video source, is perfectly stable and identical to how it was in the fully working set to within 10mV.

 

I'm getting corona out of both sets now, but nothing huge, and it's maybe to be expected given the age of everything? I'll have to clean all the bits, re-seat the plugs and the anode caps using some spark-plug grease. I realise I still haven't proved for sure beyond all doubt with 100% certainty that the flyback in the once-faulty set isn't faulty itself, and that it won't destroy the working HVR block in a matter of hours/days. Would the corona be an indication of that? Do I need an HV probe to be sure? If I had to guess, I'd say the fact the measured voltage across the working block is identical in both sets means they're operating the same, and are thus likely to be within normal range. Thoughts?

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Corona is a shit beer and you should switch to Coopers... :lol

 

You need to clean the HV lines with isopropyl alcohol, and be sures it is completely dry before reassembly. Clean the anode cap as well, and either use neutral cure silicone ( apply a ring of it on the tube bell around the anode so that the rubber cap will be sealed on near the outer edge, not alot is needed ) and allow at least 96hrs for cure before turning on the set, or use a suitable dielectric grease.

 

The silicone is not required on a direct view set as the HV isnt that high, on projection tubes it is 34.5kV in most cases.

 

It will be arcing because all that black shit is somewhat conductive, and by removing the anode leads you have disturbed it enough that the dielectric grease is likely contaminated.

 

You should really have something there, because i think these sets are pushing closer to 25kV on their HV.

 

Dont keep running the sets while theyre arcing, youll just f*** up the leads and put undue load on the HV tranny.

 

- - - Updated - - -

 

Here is what it should look a bit like if you use silicone:

 

http://i11.photobucket.com/albums/a185/Casethecorvetteman/image_zpscojhdivl.jpeg

 

Its an overkill for this, but its never going to leak HV. That tube is a Panasonic P19LUG projection tube.

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Cheers for the help and advice! The anode caps are fine, it's more the boot around the flyback lead to the HVR - which has obviously gotten black grime underneath from being shunted up and down the lead during dis/connection. I'll give it a clean, but I'm reluctant to use silicone sealant on it as I may want to change it over later.

 

Anyway, I need a replacement HVR. Sony part No.s 1-230-712-21 or 22 or better still 23 will do. I imagine we'd all normally have a few of those lying around. My excuse is that i lost my collection of them in the move to Tassie a few years back, but the rest of you need to cough up :)

 

Seriously, any tips? The parts were discontinued at least 10 years ago. I have a request for a quote in with a company in the US, but i'll be astounded if they can find anything. I can also find one listed in a gumtree-like site in Uruguay for about $60USD, but the add isn't dated, and I don't speak Spanish. I hear that another HVR from a 25"-27" Trinitron might do the job - or anyway I could test it. I'm actually thinking of calling Sony Aus and charming the pants off them, using the line that if I was an art gallery with a video wall, and *needed* to repair these sets, could they think of what we can do next, sort of making it a joint venture :)

Edited by buttersoft
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I'm actually thinking of calling Sony Aus and charming the pants off them, using the line that if I was an art gallery with a video wall, and *needed* to repair these sets, could they think of what we can do next, sort of making it a joint venture :)

 

Back in the day I was an authorised Sony repair agent and they were decidedly UN-helpful then, even to agents. I doubt they have improved.

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Back in the day I was an authorised Sony repair agent and they were decidedly UN-helpful then, even to agents. I doubt they have improved.

 

They were a bunch of twats indeed.

 

On the other hand, if you ever worked on a Barco set youd never want to go back... Every single board and part can be so easily swapped with hardly any tools.

 

- - - Updated - - -

 

Cheers for the help and advice! The anode caps are fine, it's more the boot around the flyback lead to the HVR - which has obviously gotten black grime underneath from being shunted up and down the lead during dis/connection. I'll give it a clean, but I'm reluctant to use silicone sealant on it as I may want to change it over later.

 

Anyway, I need a replacement HVR. Sony part No.s 1-230-712-21 or 22 or better still 23 will do. I imagine we'd all normally have a few of those lying around. My excuse is that i lost my collection of them in the move to Tassie a few years back, but the rest of you need to cough up :)

 

Seriously, any tips? The parts were discontinued at least 10 years ago. I have a request for a quote in with a company in the US, but i'll be astounded if they can find anything. I can also find one listed in a gumtree-like site in Uruguay for about $60USD, but the add isn't dated, and I don't speak Spanish. I hear that another HVR from a 25"-27" Trinitron might do the job - or anyway I could test it. I'm actually thinking of calling Sony Aus and charming the pants off them, using the line that if I was an art gallery with a video wall, and *needed* to repair these sets, could they think of what we can do next, sort of making it a joint venture :)

 

Ive asked a mate of mine for all the info he has in relation to this box, and to see if he can obtain one or more.

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Ive asked a mate of mine for all the info he has in relation to this box, and to see if he can obtain one or more.

 

An HVR from these sets should be numbered right - PVM2730QM / KV27HV1 / KX27HG2 / KV27HG1 / PVM2530A / MBSM27V1. Anything from a Trinitron 25"-27" might be worth a look, similar vintage preferred, I would imagine?

 

Any reason not to go ordinary spark plug grease? Thermal properties would be well in range, and spark plugs get above 25KV a lot of the time...

 

This is the most amazing community. Seriously. And that worries me. Because I'm starting to owe more favours than I'll ever be able to repay :redface

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An HVR from these sets should be numbered right - PVM2730QM / KV27HV1 / KX27HG2 / KV27HG1 / PVM2530A / MBSM27V1. Anything from a Trinitron 25"-27" might be worth a look, similar vintage preferred, I would imagine?

 

Any reason not to go ordinary spark plug grease? Thermal properties would be well in range, and spark plugs get above 25KV a lot of the time...

 

This is the most amazing community. Seriously. And that worries me. Because I'm starting to owe more favours than I'll ever be able to repay :redface

 

Youll be right, we're here to help. ;)

 

What is the part number on that faulty item?

 

Spark plug grease might be fine, give it a go i guess.

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What is the part number on that faulty item?

 

AFAIK there are three versions of the HVR, or H.STAT or "HV Resistor Assy" that would be perfect as they come:

 

Sony parts 1-230-712-21, 1-230-712-22 or 1-230-712-23

 

The -23 part is the is the latest iteration, and probably best if avail. I think the first two often suffer failures like mine's had. But a working one of any of them would be totally amazing. Let alone a few!

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