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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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That's all great info, I'll begin to work on cleaning and testing the voltage on that tonight. I have run it with the case off to look for any obvious arcing, but have not seen any. I'll do this in the dark to see if I missed anything more faint.

 

I can confirm as you suggested that after the set powers down, if you immediately cycle the power again it will turn off in about 5 seconds. The amount of time it takes to recur is definitely related to about as much time as you wait to power it back on (with a maximum up time in my case of about ten minutes).

 

In the scenario where the H-stat is confirmed bad, has anyone found any viable replacement parts from other sets that are confirmed working? The PVM 2030 to me clearly looks like a unit that has different specs (it's about half the size). Many have suggested there are other trinitrons of the era that use a similar unit, but I have yet to see a confirmation that any of these are rated correctly to work on this set without issue.

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Well I have a couple of updates based on information you provided below, so I'm trying to decide what direction I should go from here:

 

 

But if the HV was leaking from either the cable or the anode cap, you probably wouldn't be getting shutdown but rather, if anything, a stutter to the image size or brightness. However, the best way to be sure is to run the set with the case off in the dark - even an HV leak too small to affect the picture will produce a visible purple glow around the leak, if not actual arcs, though you may have to get close - while staying at least a foot away to be safe.

 

I tested this first, and in total darkness there is no glow at all around the unit, so I guess it's not leaking to that extent. There's also no visible arcing anywhere, and nothing visible on the back of the unit at the point of it shutting off.

 

If there is a problem, or you want to clean things anyway to make sure there isn't, then with everything powered down and disconnected you discharge the tube safely, and then remove the anode cap and clean everything with isopropyl and reseat. There is a sketch of the shatter hook on the back of the rubber anode cap - it's a solid white plastic centre with two small hooks on it. You probably want to peel back the anode cap from one side, and push the straight side of the metal hook that's visible against the white plastic back toward the direction of the lead. Once one side of the hook comes out, the whole thing should release. Be careful because the lead is actually coax, with a centre connection under the white plastic that connects to a little spring - the spring doesn't come loose, but idk what you'd need to do if you break it.

 

I'm glad you told me about the spring, I would have perhaps tried to get that out, but that was good info. I removed the anode cap first thing when I got home tonight because I wanted a better look at this H.Stat and the inside of the tube is too dirty for me to live with. So I'm cleaning now in addition to some notes below.

 

 

Do not twist the lead too hard or you will wrench it free of the H-stat, and that's also instant failure :) It should not twist or turn in the socket, where the red-coloured flyback lead can be pushed in and then twisted slightly to release or reinsert.

 

This right here might be a big problem for my H.Stat. The white anode cable on mine twists freely with no effort, I noticed it while I was taking the cap off. Is this indication of the decay that has been done from this failing? And you're right about the white wire having natural discoloration, mine does have that. But it has a lot of straight black on the inside that looks pretty awful as you mentioned.

 

 

 

You can test the H-stat by following where the grey coax leads from underneath the H-Stat to the bottom of the D board, and then putting a voltmeter across those two relevant pins on the connector (The ones left over when you subtract the the ground wires and the wires that form the loop on the connector). You can do this from the back of the D-board, that way you're not trying to get your hands in there. Just remember that the D board has a few kV points on it, so don't go poking around randomly just yet. While the set is in operation, the voltage should be stable at about 3V - 5V, i think. If the voltage is drifting, see what happens, and where it gets to before the set shuts down, and if this happens the same way at the same voltage every time.

 

Haven't gone this route yet. I am wondering based on my finding of the white wire above moving so freely if this is even a step I should take at this point. Your mention of this causing failure makes me think that this unit might be toast, that seal is absolutely broken there.

Edited by LuckyDay
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... might be a big problem for my H.Stat. The white anode cable on mine twists freely with no effort, I noticed it while I was taking the cap off. Is this indication of the decay that has been done from this failing? And you're right about the white wire having natural discoloration, mine does have that. But it has a lot of straight black on the inside that looks pretty awful as you mentioned.

 

I have to admit that the white lead wouldn't move on any of the H-stat's i have - save that one i repaired. I would definitely advise being gentle with it. It's coax, and i really think i got lucky when trying to put it back together, as my account of doing so notes.

 

The H-stat is used to adjust horizontal static convergence. Have you tried it out while the set is running? Make sure to wave your discharge lead around the knob first, while a picture is up, to make sure nothing is going to zap you. I realise i haven't asked before now if the image is ok while the set is operating, but i presume you'd have mentioned that. I think there's a photo back on page 2 of this thread that will show you what should happen as you twist the knob.

 

If the knob is still working normally, i would guess that the lead might be lose, but it hasn't torn yet. Again, be gentle, because you don't want to tear it now! I guess it's possible that versions were made where the lead would detach the way the cable from the flyback does, but i haven't seen that. It's also possible it's in some sort of housing that rotates and is meant to do that - i hope so, anyway.

 

I still think it's going to be resistor decay within the block of resin that comprises the main body of the H-stat though, if it is the H-stat that's at fault. HV leakage in the leads or anode would tend to be either catastrophic and visually or audibly noisy, or else the sort of small surprise you won't know is there until it gives you a nasty nip. It wouldn't be a "slow" leak of any sort. EDIT: thinking about that, however, there are cases where a flyback can take 5-10mins to warm up, normally reflected by the picture drifting into or beyond focus. I've only heard on it on arcade chassis flybacks, but i guess it's not impossible. But if you're not having focus issues and you don't have or can't make an HV probe, it's easier to eliminate other problems first.

Edited by buttersoft
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You should be using a plastic screw driver to adjust anything on the HV side, metal screw drivers will potentially affect the adjustment due to their magnatism, also you risk inducing a voltage into the metal screw driver, which will either make it get bullshit hot, or itll boot you.

 

This certainly goes for adjustable coils too.

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I removed the anode cap first thing when I got home tonight because I wanted a better look at this H.Stat and the inside of the tube is too dirty for me to live with. So I'm cleaning now in addition to some notes below.

 

I hope you aren't cleaning the aquadag (grey, slightly powdery paint) off the back of your tube - It is meant to be there. It is conductive so that any stray voltage that develops can be easily grounded (via the metallic & usually spring-tightened grounding strap that "hugs" the aquadag and back of the tube).

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The H-stat is used to adjust horizontal static convergence. Have you tried it out while the set is running? Make sure to wave your discharge lead around the knob first, while a picture is up, to make sure nothing is going to zap you. I realise i haven't asked before now if the image is ok while the set is operating, but i presume you'd have mentioned that. I think there's a photo back on page 2 of this thread that will show you what should happen as you twist the knob.

 

Yes the knob for the static convergence does work correctly. There is a very slight horiztonal convergence issue on one corner that I'm not very worried about, but doesn't seem to be a symptom of this problem.

 

 

I still think it's going to be resistor decay within the block of resin that comprises the main body of the H-stat though, if it is the H-stat that's at fault. HV leakage in the leads or anode would tend to be either catastrophic and visually or audibly noisy, or else the sort of small surprise you won't know is there until it gives you a nasty nip. It wouldn't be a "slow" leak of any sort. EDIT: thinking about that, however, there are cases where a flyback can take 5-10mins to warm up, normally reflected by the picture drifting into or beyond focus. I've only heard on it on arcade chassis flybacks, but i guess it's not impossible. But if you're not having focus issues and you don't have or can't make an HV probe, it's easier to eliminate other problems first.

 

I think you're right, leakage at this point is probably not the problem. The TV is hooked back up at the moment, I'll look into testing the value on the resistor when it fails tonight. If it's failing, I guess that means I'm looking for another H.Stat.

 

- - - Updated - - -

 

I hope you aren't cleaning the aquadag (grey, slightly powdery paint) off the back of your tube - It is meant to be there. It is conductive so that any stray voltage that develops can be easily grounded (via the metallic & usually spring-tightened grounding strap that "hugs" the aquadag and back of the tube).

 

No, I'm not cleaning the actual back of the tube, I just meant inside the unit as a whole. The previous owner had this sitting for a while unused, and the back was off. So the wires and boards themselves are just full of dust, as well as the metal frame. This is what I'm wiping down with alcohol and air dusting.

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You can test the H-stat by following where the grey coax leads from underneath the H-Stat to the bottom of the D board, and then putting a voltmeter across those two relevant pins on the connector (The ones left over when you subtract the the ground wires and the wires that form the loop on the connector). You can do this from the back of the D-board, that way you're not trying to get your hands in there. Just remember that the D board has a few kV points on it, so don't go poking around randomly just yet. While the set is in operation, the voltage should be stable at about 3V - 5V, i think. If the voltage is drifting, see what happens, and where it gets to before the set shuts down, and if this happens the same way at the same voltage every time.

 

Had a bit of a delay before I could get back into this due to a family medical emergency, but I'm back into the research here.

 

So before I go poking and prodding around with my voltmeter, just want to confirm that I've got the correct points here as labeled in my picture below, this according to what is shown on the back of the board in relation to what is in the connector:

 

HVRLeads.jpg

 

IMG-7915.jpg

 

 

If I understand correctly I should show 3V-5V between HVR1 / HVR2. E looks like the grounds, and +140V is to be avoided.

 

Have not been able to get around to doing much cleaning down at the bottom of the internals as you can see, still filthy down there.

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Sounds right to me. You could meter the 140V to ground if you want to check it’s at about the right level too. But you’re primarily interested in the voltage between HVR1 and HVR2 while the set is running. In my case putting the 10M voltmeter across them acted as a slow short, and the set would shut down even faster than the 30 minutes it was taking. In any case, write down what the voltage is doing and when the set shuts down, then wait half an hour and go again and see if it's always the same.

 

If that voltage looks stable, but the set is still shutting down, you could also try metering each of HVR1/2 to ground.

 

Stay well away from everything you don't want to be touching, of course, there are any number of nasty voltages on the D board.

 

EDIT: Now i think about it, you want to make sure the visible image on the screen stays the same (until shutdown) as in no convergence going weird or strange colours coming up or geometry warping. And you also want to check that the 140V isn't drifting either. This could help isolate the problem.

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Sounds right to me. You could meter the 140V to ground if you want to check it’s at about the right level too. But you’re primarily interested in the voltage between HVR1 and HVR2 while the set is running. In my case putting the 10M voltmeter across them acted as a slow short, and the set would shut down even faster than the 30 minutes it was taking. In any case, write down what the voltage is doing and when the set shuts down, then wait half an hour and go again and see if it's always the same.

 

Bingo. I'm working from home today so I've tested this a few times over the course of the morning, and my results sound very similar to yours.

 

The voltage while the set is running fluctuates between 3V-5.5V, but within minutes of me holding the voltmeter on the two HVR1/HVR2 points it shorts. At the moment it shorts, it gets to 6-7, then back down to 0 while the screen is in standby. Repeated three times so far with similar results.

 

As you mentioned, when I do this, it doesn't wait the 30 minutes to shut down, it's much faster (maybe 1-2 minutes max).

 

The +140V seems stable against the ground.

 

Any suggestions on next steps?

 

*note, as far as I can see, I'm not having many issues with the actual display while it's running, both while it's warming up and just before it shuts down. It's also hard for me to hold the voltmeter on the board at the same time as looking at the screen, so I may be missing it.

 

But to my eyes, the display looks nice from the point it's running well to when it shuts down. When it's turned back on after shutting down, it does need degaussed.

Edited by LuckyDay
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I don't believe there is a standby mode on these sets, the HV section has shut down after detecting what it thinks is a critical failure. So there's no voltage going through the H-stat, and the HVr1 and HVR2 lines read 0V between.

 

With my faulty HVR, the difference would start at between 9 and 12 volts, which would slowly fall until it got to about 3.5v where the HV would shut off. You're getting similar behaviour from the sound of things, yeah. Where does yours shut down?

 

I guess at this point i'm trying to make sure the HVR is the faulty part and not the flyback (the HV LOPT transformer). You've checked that the flyback primary supply is stable at 140V. The flyback itself being faulty would probably have an effect on picture size, shape, brightness and/or convergence in this set (the last thanks to the HVR/H-Stat). So it might be important that you watch the set from power up to when it shuts down - you don't need to be measuring the HVR1/2 voltage, but if you want to you could use a mirror or another person mb :)

 

I don’t suppose you have access to a high-voltage probe or similar?

 

I think it’s going to turn out to be the H-Stat, and I have a repaired one I can sell or trade, but I’d like to be 110% sure. I'm kinda hoping someone else can weigh in with a more solid idea on how to test if the HV itself is drifting.

Edited by buttersoft
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Yes you're right, no standby mode, that's just what it acts like.

 

My voltage is similar, but seems to happen a little faster, it doesn't slowly fall, it just sort of drops entirely. I thought it was shutting down around 6V, but I'll check that again today to see if I can pinpoint it.

 

Flyback is stable and the picture has what I would consider standard geometry issues (a bit of PIN being off on the top), nothing a TV of this age wouldn't typically have due to Caps starting to go. Brightness levels are great. The top right side of the TV (maybe 5-10mm from the corner) has a small area where convergence is off, but it's hardly noticeable.

 

I don't have a high voltage probe unfortunately.

 

Today I'll test the following: Exact voltage the set shuts down to confirm, and what the picture does for the entire duration of it running. I'm confident the picture doesn't change because I noticed this originally during use of the set, so I was looking at it and don't recall anything off about the picture.

 

I'm curious, you mention you have a repaired HVR, how did you go about getting this repaired? Did you do this yourself or take it to a service center of some sort? If I definitely need one I'd certainly be willing to buy yours, but I'm also interested now if repair is also an option for these. They are getting more and more rare as I'm finding.

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Tested a few more times today. Similar to what you describe but not the exact numbers. Mine only ever gets to around 7-9V max (higher than my original test where it only got up a bit past 6V) before declining and shuts down around 3V from what I can tell. I tried to record the voltmeter with my phone and realized I had it set on 4k video, so it's huge and won't upload here.

 

I did manage to get a video of the display on screen during operation and when it shuts down. No deformities or anything that I can see. The picture itself isn't as clean as it could be as I haven't yet adjusted any settings on this set (since it wasn't working correctly when I got it).

 

https://photos.app.goo.gl/6HVEZYBToHhBTZGN6

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Yep, I'm happy with that testing. I reckon your problem is the same as mine, and the H-Stat has some sort of degradation or damage that sees the components inside it change value while everything is powered up, eventually leading to the set shutting down. Which is ironic given this was the watchdog on the HV section.

 

I acquired a replacement H-Stat from Uruguay, and the anode lead twisted and tore free. I used graphite-paste wire glue to fix it, which i'm not going to deny was almost pure ass given the lead is coax and i had to force it back into a narrow socket. I then used superglue around the socket shroud to ensure the lead can never come loose again. It gives consistent results, the potential difference between HVR1 and HVR2 remains at about 4.6VDC IIRC while it's running, the picture is stable, and the potentiometer works to adjust horizontal static convergence like it's meant to. There is no corona or leakage. The only problem might be a tiny shift of R & B vs Green, but I might be imagining that as when i swapped it there was no noticeable difference.

 

I've since found a NoS unit on Ebay with thanks to Claude, and i now have three working 2730's, two active and a spare. So i have the repaired H-stat i'm prepared to part with at this point as i acknowledge that your desire to have a working set outweighs my need to keep a second spare :) I used this H-stat for two stretches longer than 5 hours in mid 2017 and mid 2018 (to see if anything positive happened to the colour bleed problem also described in the thread) and with this H-stat in place i turned the set on numerous other times for shorter lengths over that period. As far as i can tell it works fine. I make no claim that it's anything but what it is, in the condition it is. I'm also not a TV repairman, so while i think i know what you're problem is, it's up to you to decide if you wish to take the chance on it.

 

It looks like the H-stat's all come without the cable doing down the the D board, so you'll need to unsolder that from your current one and solder it onto the new one. Not hard, but there's big chunks of old solder on there. I'll have to pull it out of storage to check the exact part number, but it's one of the three sequentially-numbered models (Sony part No.s 1-230-712-21 or 22 or 23) and all three are interchangeable from what i understand. If you're interested, please send me a PM with the model number printed on yours, and we'll see what we can work out.

 

Before that, i'd suggest fishing around to see if you can find one new in box or not repaired by me :D Old TV repair shops, ebay, online, whatever. When you look at it i've bought two in two years, so i can't speak for the odds.

Edited by buttersoft
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Yep, I'm happy with that testing. I reckon your problem is the same as mine, and the H-Stat has some sort of degradation or damage that sees the components inside it change value while everything is powered up, eventually leading to the set shutting down. Which is ironic given this was the watchdog on the HV section.

 

I acquired a replacement H-Stat from Uruguay, and the anode lead twisted and tore free. I used graphite-paste wire glue to fix it, which i'm not going to deny was almost pure ass given the lead is coax and i had to force it back into a narrow socket. I then used superglue around the socket shroud to ensure the lead can never come loose again. It gives consistent results, the potential difference between HVR1 and HVR2 remains at about 4.6VDC IIRC while it's running, the picture is stable, and the potentiometer works to adjust horizontal static convergence like it's meant to. There is no corona or leakage. The only problem might be a tiny shift of R & B vs Green, but I might be imagining that as when i swapped it there was no noticeable difference.

 

I've since found a NoS unit on Ebay with thanks to Claude, and i now have three working 2730's, two active and a spare. So i have the repaired H-stat i'm prepared to part with at this point as i acknowledge that your desire to have a working set outweighs my need to keep a second spare :) I used this H-stat for two stretches longer than 5 hours in mid 2017 and mid 2018 (to see if anything positive happened to the colour bleed problem also described in the thread) and with this H-stat in place i turned the set on numerous other times for shorter lengths over that period. As far as i can tell it works fine. I make no claim that it's anything but what it is, in the condition it is. I'm also not a TV repairman, so while i think i know what you're problem is, it's up to you to decide if you wish to take the chance on it.

 

It looks like the H-stat's all come without the cable doing down the the D board, so you'll need to unsolder that from your current one and solder it onto the new one. Not hard, but there's big chunks of old solder on there. I'll have to pull it out of storage to check the exact part number, but it's one of the three sequentially-numbered models (Sony part No.s 1-230-712-21 or 22 or 23) and all three are interchangeable from what i understand. If you're interested, please send me a PM with the model number printed on yours, and we'll see what we can work out.

 

Before that, i'd suggest fishing around to see if you can find one new in box or not repaired by me :D Old TV repair shops, ebay, online, whatever. When you look at it i've bought two in two years, so i can't speak for the odds.

 

That would be fantastic, I'll definitely message you. Shipping costs hopefully won't be too terrible since the part is fairly small.

 

I've been looking at this point for about 3 weeks for a replacement online, they are very scarce at this point. The best lead I had so far was an employee from Encompass who is the official Sony parts distro here in the U.S. He claimed to have a garage full of PVM parts that he'd look through, but after 2 weeks of waiting for him to get back to me on that, I think that's a dead end.

 

Another user on Shmups also purchased a 'compatible' part that he believes should work with it, but I'm less confident about an H.Stat from another set working correctly, unless it's a set that's exactly comparable in size (in my mind the resistor would have to spec'd to the correct voltage coming from the size of the tube).

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So, tonight we have some updates to my H.Stat issue.

The symptoms:

 

Set would turn off after anywhere between 2-10 minutes after starting it up. The set stayed powered on, but the tube would go black and lose picture. No audible sound for this other than a small hiss (standard for a tube discharging).

 

After troubleshooting with buttersoft above, and with his help, we determined the H.Stat unit (or HVR/High Voltage Resistor Assembly) was bad on the set and needed replaced. He was kind enough to sell me an extra part, as finding one online was a real problem, if anyone else needs one of these, you're going to have some real trouble finding a replacement at this point (more on that later).

 

The Fix:

 

Here's what the original part looked like, note the dark black areas, especially in the anode line. These are all inside of the cabling, not on the outside (so not simply dirt). This looks to me almost like burns on the wire. I've seen pics of other units online and they do have some discoloration, but I haven't seen one this bad yet. Ignore the epoxy, I originally tried that trick which is used to prevent HV leaks from the line.

 

IMG-9046.jpg

 

IMG-9045.jpg

 

Here's the new unit installed on the set. This one looks pristine, and new or nearly new. Model # is the same, but from what I've read elsewhere, the orange color is a later version of the same part. Makes sense as this TV was in circulation and being sold/supported by Sony for somewhere around 8-10 years. Installation involved re-soldering the wires as shown here. This required a little bit of precision on the stripping as these wires are old and brittle, and cut to length. I was a little worried about accidentally snipping them and not having enough length to reach the contact points.

 

IMG-9037.jpg

 

The result:

 

The TV has been running Sonic demo now for about an hour with no issue. When the part was originally installed I did have to do a decent amount of fine tuning on both the H.Stat dial itself, and the Vertical Hold adjustment on the back of the set (as well as 1-2 pass with the degauss). A definite improvement from where it was before. I'm hopeful this has solved the issues, and to this point things are looking good.

 

Once that's done, I'll move to color correction and calibration. Geometry on the set looks fairly good so far for not being used for a while (previous owner had it sitting in storage for years. He says because he didn't get around to it, I suspect because it was "broken" with this issue and he never solved it or bothered fixing it).

 

No noticeable issues yet with convergence, color bleed, etc. Ignore my terrible CRT photography skills.

 

IMG-9039.jpg

 

IMG-9054.jpg

 

 

Thanks again to buttersoft for his generosity in letting go of a part that isn't easy to come by, as well as anyone else who helped solve his original issue in this thread. These sets are not extremely easy to find info for troubleshooting online, and this forum has been an amazing help.

 

Looking forward to now getting this thing in tip top shape and being able to move on to other parts of this project.

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Sounds like it's all worked out :) I'm really glad the part arrived ok and seems to be working. I'd still put your voltmeter across the HV1 and HV2 terminals and see if they're stable every half hour or so.

 

Don't be a stranger. I'd be happy to help with any future issues, though i should warn that i don't often get the opportunity to disassemble one without a few weeks of planning to free up the time. I assure you my interest is purely selfish - i have three of these and want to keep them running :D

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i have three of these and want to keep them running :D

 

Good luck, you'll need it. Having 27" sets doesn't sound like a good idea because of the older tube design with horizontal static adjustment through the anode button with external components (the red box). At the end of the 80s Sony must have thought it was a bad idea and changed their design by putting the HSTAT resistor in the neck and having just an external 110Mohm trimmer to adjust the HSTAT through a pin on the neck base. And when they did so they also stopped making 27" tubes for good and started with 29". This means that if a TV or monitor has a 27" tube that goes bad it can only be replaced by another old 27" tube. Owners of a PVM 2950 on the other hand could swap the tube with any other newer 29" tube as they're all designed the same way.

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Well, technically it's two and a spare, but having all three working for the first time does feel nice. The tubes seem to be in good condition, though when i went looking it seemed there was pretty much zero chance of getting a spare - which would weigh like 40kg anyway and i'd have no room to store it. Always interesting to hear the history behind the hobby though; i had noticed the change from the big red external H-Stat's to the smaller pot on the neckboard. I figured that was to do with failure rates, an old jack-of-all trades type of electronics repairman i knew turned out to be an old Sony agent, and when i was looking for an H-stat for my sets he mentioned that when he used to order them one in five would come pre-cooked, as it were.
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Last week or so, I *finally* got those resistors to replace the solid carbon neckboard resistors on my Sony PVM2730. Between being busy and being sick this week, it's taken me a while to get back to the job.

 

As it is 2 months since I last looked at this, I went back over them all again and found... the only resistor that really looked bad was R702 (470k). The rest were still within 10% of spec. I also went over the electrolytic caps with my ESR meter again, and decided that C704 (22uF, 250v) and C766 (100uF 50v) looked bad. On removing the caps, C704 proved to be a dried husk, had been leaking from 2 holes in the bottom. C766 was dying too, but hadn't leaked.

 

Sonyneck2.jpg

 

So, I replaced these yesterday (R704 with 470k/2W metal film resistor; C704 with a 22uF/450v low ESR cap; C766 with 100uF/50v Rubycon cap) while still recovering from this crippling gut bug, then crawled back into bed.

 

Went back to test everything, first power-up in 2 months, and... not good news. Got complete vertical collapse (solid white horizontal line). It just kept getting brighter and brighter so I turned it off after a few seconds of this. I think I might have heard an unusual faint sucking sound just before the degauss coil buunnnnnged.

 

Went back to inspect my work, and found that I'd made a mistake with C766 - got the polarity reversed in my fevered state! So I rectified that and fired everything up again and... complete vertical collapse.

 

vertical collapse.jpg

 

So now I have vertical collapse to deal with! I'm not sure if accidentally reversing that capacitor had anything to do with it. It may have just been waiting to happen, and 2 months sitting in my shed was just the trigger it needed. Also worth noting that I've thoroughly gone over the electronics with compressed air to blow away crap that has layered on over the decades, so wondering if I somehow upset something doing that.

 

It actually got a bit brighter than in the attached pic, but then I turned it off.

 

Anyone have any tips on what I could do next?

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C766 is part of the beam current limiter circuit, so it's perhaps not surprising that the pic kept getting brighter and brighter. I would guess that the vertical collapse is unrelated, or only very slightly related at most. Either way it's what you have to deal with now :(

 

The service manual shows the schematics, of course. Sadly on these sets the deflection sections look like an absolute nightmare.

 

I'd try to check the connection/leads to the vertical yoke, and then before that the vertical deflection voltage goes through the D2 board, and then to the main D board. The compressed air might have knocked something loose. I'd check the relevant sections of both those boards, and maybe desolder and test the Vertical Bias and Vertical Out transistors. There are some electrolytics in that section as well, but it feels more like an absolute failure though, as the signal at the yoke would seem to be dead, not just weak.

 

I don't *think* it will hurt to have the set on for short periods, but i'm not sure. And it will start to burn that line in if nothing else. But running it might allow you to check some voltages, and see where the signal dies when it comes to the connectors, which should help narrow down where the faulty component(s) is. I'd think you were in better shape to keep the set running if the fault is on the D2 board (signal dies between it's input to that board and it's output to the yoke) but again, i'm not completely sure. The vertical section of the D board has the 140V B+ going through it, and the D2 boards is going to be live too, so watch yourself.

 

If you come up with any particular bits that you want to compare, let me know and i'll open up my spare 2730 and check for you :)

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@buttersoft thanks or your reply.

 

I suspect that I was just being a bit paranoid about the "brighter and brighter". I didn't let the set run for more than about 10 seconds, and it was probably just warming up still. The line will be very bright of course, because it contains a whole screenful of picture.

 

When I took that photo it obviously took me a moment longer to switch of the Sony, and the brightness seemed to stabilise for a moment before I did so. I'll be brave and try keeping it on a bit longer.

 

I think I'm going to have to go over the connections to the "NECK ASS'Y" first - those wires got pulled a bit from time-to-time when dealing with the neckboard ©, though nothing too dramatic. Then all other connections. Then I guess time to set up a mirror, leave the Sony on, and start tapping around with a wooden spoon (loose connections, cold solder), starting with the C and D boards. If that shows nothing, then I guess I'll be looking for those vertical bias/out transistors you mentioned.

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feed in a black signal for less burn-in. And try to work as fast as is safe while the set is on. I really hope it's safe to power up, like i said.

 

I also not that the vertical signals pass though the D2 board directly (although with possible voltage or current influence from the circuitry on that board). So you can just meter the connectors on either side of the D2 board, and then from the D board right to the Yoke. That should get you started

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So I think I'm good to go with the H.Stat unit fixing my powering off problem. Over the past few weeks I've tested in multiple 2-3 hour tests and haven't had a single issue.

 

Now I'm moving on to some general maintanence. I have a couple of geometry issues I wanted to throw out to the group to see what people thought about possible solutions.

 

The picture on the set still looks great when in action, the problems below aren't very noticeable on most screens. In something like Zelda where you have a very defined square playing field, it's more apparent, but in general it's hard to see in action.

 

Here's a picture of the geometry at the moment, second picture has the areas I'm having trouble resolving circled:

 

IMG-9768.jpg

IMG-9767.jpg

 

 

- The waves at the far top of the picture indicate capacitors on their way out. That's on the agenda for the future (there's a highly recommended repair center around here that I'll be using to do a full tune-up), but for the moment I'd like to correct some of the "wave" moving through the vertical lines on the picture circled above.

 

- PIN/T.PIN/B.PIN can all correct minor portions of the corners, and in fact the corners themselves looks fairly good right now (they're 90degrees at least), but it's closer to the middle of the line that I'm having trouble finding solutions to.

 

- Is there a parabola/trapezoid equivalent setting on this set like later models have? I'm unable to find anything on the side board that can be adjusted with pots.

 

- The squares on the right side of the set are slightly slimmer than the left size. What setting would be used to equalize the horizontal spacing on the picture, if there is one?

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The sizing of the squares is adjusted by H-LINEARITY.

 

The sides of the image like they are is something ive struck on a few Sony sets, and i was not always able to get it perfect. I have a Sony here right now that looks pretty simular to that on the sides, im not convinced capacitors are going to be all that is either.

 

What you can try is adjusting PIN to get the middle better, then fix top and bottom with T-PIN and B-PIN, its a fine balancing act because there is limited adjustments, i reckon you may have room for improvement there yet.

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