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

  1. #1

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

    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 US PVM-2530's, possibly the PVM-2550's and the KX27HG1 and KX27HG2 sets, along with the Japanese Profeel sets that look the same. 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!
    Last edited by buttersoft; 8th January 2019 at 11:12 AM.

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    I had one of these and it was very tired, you're on the right track the only other thing I can think of is a cold solder joint.

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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.
    Last edited by buttersoft; 10th June 2016 at 11:18 AM.

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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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    nice find, i wouldnt have a clue .

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    Quote Originally Posted by buttersoft View Post
    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.
    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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    Quote Originally Posted by Homepin View Post
    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

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    Quote Originally Posted by Homepin View Post
    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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