Don't dump your CRT RPTV! - Page 431 - AVS | Home Theater Discussions And Reviews
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post #12901 of 12908 Old 03-01-2015, 01:10 AM
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Warning - tl;don't read

Bob, I kinda ramble in my posts - I'm sorry, I do try to edit a little - and I don't expect you or anyone else to read or respond to me at all so your feedback has been very appreciated.

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Originally Posted by Mr Bob View Post
Are those the only numbers you can use? Usually FBTs have big long strings of numbers, which is what should be used on an ebay search. Or search anywhere, not just ebay. Many manufacturers of such things may have them and not use ebay. At this point even knockoffs would be better than nothing, and your search may need to go offshore.
The thinking behind the faulty FBT was that adjusting the horizontal size, the trimpot for which is on the power board, would only reduce the horizontal size at the corners *very slightly* and not at the horizontal midline at all. It would also only make this tiny change when adjusted to the maximum. Then, as you are watching a show, you see the horizontal sort of stretch and shrink in those corners, making you question if you are now paying for all of the drugs you did earlier in life. Vertical size adjustment works fine.

I heard somewhere that this can be a voltage clipping problem and that the FBT would be the most likely cause. I did find two resistors on the power board that had burn marks on the PCB at their solder joints when I reflowed the board but they tested fine. Replaced them anyway, no change. Fuses look good, all caps look good. Next step is to trace the horizontal size circuit (I do have the SM) and make sure everything is in spec, I guess.

Originally I wanted to focus on the convergence problem first, but I'm just wondering if this isn't a voltage problem at the root of all my issues. I suppose I should find a way to get a scope over here.

Quote:
What do you think is the bottom line of what helped on that CRT ECB issue? Caps being old and dried out? Weak solder joints?
Bad solder joints, no question. You could see that several joints on the green and blue were going even without magnification. The caps tested fine on my multimeter, but I didn't like the way they looked and I had spares.

After reflowing those CRT PCBs, the brightness of green and blue went up significantly. The entire image just seemed to be more vivid and focused.

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I have seen the pincushion circuit be badly cold solder jointed on certain units because it runs so hot. Can't remember which brand I found that on, tho. Definitely check for cold solder joints in the pcush circuit.

That said, that advice is primarily for master pincushion. For just the green, you'll probably have to look at replacing the convergence ICs. They are multiple-channel devices and can go out on certain aspects while remaining OK on others. Same is true for the colors. I would replace the convg ICs before doing anything else on that score.
The pincushion issue is "interesting". I've managed to make iterative improvements to it but not eliminate it completely.

All the colors are pincushioned, but blue and red can be adjusted freely in the service menu and get close to correct. Green is adjusted by a series of six trimpots on the convergence board itself, all of which I scored before touching so that I could come back to stock. Four work perfectly. The horizontal PIN adjustment gets close, but requires being cranked close to it's maximum. The vertical pin adjustment has essentially no effect.

The original convergence amp was unquestionably bad. At the current moment I've got a fully functional (I think) STK-4277-SL from Audio Lab of Georgia in there. I did order a kit from TVrepairkits.com per your suggestion, but they sent me the wrong one. When the correct one gets here, if I haven't found the solution yet, I'll give their amp and resistors a try.

I've reflowed the entire board twice, replaced every electrolytic capacitor, replaced all the large resistors (only the piggybacked one was out of spec), and replaced both voltage regulators. I did everything in small increments so I could attempt to isolate the problem as I went. The next step is checking and replacing all the ceramic caps, especially the ones on the green circuit near the amp heatsink.

I should mention what prompted that second convergence board reflow. One day I turned the set on and was watching something, ten minutes in the pincushion vanished for a few seconds, then stretched back to where it's been. I assumed this was a heat-expansion-poor-contact thing and that I must have missed something. So I gently probed every component on the board and the board itself while watching the screen. No effect noted. Went back and reflowed the joints for the second time. No change. Pulled the amp, checked all the resistors, and then tried another convergence amp, with no change.
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post #12902 of 12908 Old 03-01-2015, 12:58 PM - Thread Starter
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I am glad you are adept in such things. Even I have caused solder bridges in the past just once at a time, so these days I don't touch anything that does not need to be touched. I have been lucky so far, but one owner tried to resolder his Pioneer Elite CRT PS board, saying he was a tech by trade, and left 2 bridges in there. Even I missed the second one first go round, but finally caught it. Unfortunately one of them - or maybe the combo - must have taken something out, because now as soon as it is turned on it starts into runaway screen voltage on all 3 guns; starts slow but ramps up and after a minute or 2 they are so lit up with background gray that the set shuts itself off. Fortunately the protection circuit didn't get compromised. But we don't know what did, and for now I have kicked it back into his court to find where D218 is, as it being directly shorted is where I found the second solder bridge. It's OK and the 100 ohm resistor in series with it is also OK, but something got damaged by those 2 solder bridges being still there when it turned on. Its auto regulation circuit is toast.

That said, I can't wait to see your finished set!

I looked at the pix, and your entire vertical pincushion is disabled, offline, non functional. It's not just the green, it's the master vertical pincushion. If it were just the green, the green image would be separated from the purple image. It's not. If it were a failure of the entire convergence sys, the blue and red images would be all over the place - mirror imaged with each other but neither corresponding to the green.

The entire picture is pincushioned in at the top and bottom meaning that whatever controls all 3 is what's at fault. As such I doubt it's your convergence, unless there is a master convergence register for vertical pincushion. Pioneer did not do what Mit did and make the blue and red follow the green automatically, when in geometry mode. If it were in the convergence there would be separations of the 3 images, but all 3 are still tightly together even tho vertically pincushioned.

b

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post #12903 of 12908 Old 03-01-2015, 01:50 PM
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Quote:
Originally Posted by Mr Bob View Post
But figuring out which one it is, is the challenge! Repairs on panels needing repair usually exceed the cost of replacing them these days.

If your set is perfectly operational, someone should jump on it. An old analog 27" DV is no comparison, as it won't even be HDready!

Tho I must say my 26" Mit direct view CRT in the bedroom continues to deliver excellent, lifelike colorations, excellent grayscale and a nice crisp picture for before-bed viewing, every night. It's at least 20 years old and still hanging in there with never one problem, and due to my calibrating it many years ago it still looks better today than the day I bought it! I keep the Contrast at 40% - have to readjust that back down every time there's a power outage at the house, because it defaults back to max when the power goes out - and the brightness exactly where it should be - blacks are crystal clear black with more than enough shadow detail in the mid grays to be consistently effortless viewing - and I would not want to part with it. I am about 7' away, eyes to screen, and doubt having an HD set of its size at that distance would ever make a difference. Closer up maybe, bigger maybe, but that size at that distance - nada.

b
No bites. Most looked at the big box size and decided it wasn't for them or anyone they knew. A couple weeks back someone inquired on NextDoor.com if it was still available because the TV in their daughter's bedroom died and they wanted to get something she could play games on. Obviously a 53" didn't fit the bill.
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post #12904 of 12908 Old 03-01-2015, 02:12 PM - Thread Starter
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That old 27" analog TV would have been perfect!

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post #12905 of 12908 Old 03-01-2015, 03:44 PM - Thread Starter
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This is about the Pioneer CRT RPTVs that led the class back when HD was still new in this country - the PRO 510HD, PRO 610HD and PRO 710HD, and the first half of the model year the following year, the PRO 520HD, PRO 620HD and PRO 720HD. And the non-Elite versions, which used the same board, the SD 532HD, SD 582HD and SD 642HD plus, the following year, the SD 533HD, SD 583HD, and SD 643HD.

They are still going strong, but most have had their power supply boards resoldered, primarily because the solder used on that particular board back then was too thin, resulting in cold solder joints later which made the units very unstable until it got worse and damaged something. Resoldering that one board adequately made the set stable again for life.

This is about post 12902, above, where I talk about something that an owner missed on inspection of his work, after resoldering his own board.

The first two pix are of the 2nd of 2 solder bridges I saw and corrected. The third pic is the corrected solder joint without the solder bridge. That is the way it should be.

I know the first 2 are a bit hard to see, but trust me, I did a continuity check on it, and D218 was fully shorted. Which saved it of course, it checked out fine once again at last picture status. But that diode being shorted took out something downline from it, causing the Screen voltage runaway and making the set unusable now, until corrected.

This was done by an owner who declares himself a tech by trade, and it happened even to him. If you are not a thoroughly seasoned and experienced technician or solder person - like you work at Tektronix and solder every day, like I did before I became a service tech - I advise you to NOT try this yourself. As I have said before, there is far too much riding on it. Send it to me and have me do it.

Click on each pic to blow it up.

b
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post #12906 of 12908 Old 03-01-2015, 05:17 PM - Thread Starter
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This is the 1st solder bridge the tech left, very tiny and not easy to see, but crucial because it threw the set into protection until corrected. Can you spot it? Pix are before and after clearing it.

Again, click on each pic to blow it up, so you can really see it after it has opened up in your player's window. 2 separate clicks are needed to see it blown up.

If you cannot spot something like this when inspecting the board close up and personal, you should not be doing this job yourself. You will have to triple inspect the PS board before you hook it up and turn your set on again. If you miss it, who knows what will happen to your set? In this case, that owner's set is down for the count until an actual troubleshooting operation, involving service manual and testing, can be performed and repairs implemented once the problem has been found. The protection circuitry in that unit was designed to protect from incorrect operation as designed, in case something went bad in it. The protection circuit was evidently not designed to protect the set from a different design, which is what happens when one of the many diodes in the set gets directly shorted from the outside!



The design changes.

Perhaps the diode would short on its own someday, but I have never seen it short by itself, in over 10 years of resoldering these boards.

Send it to me.

b
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post #12907 of 12908 Old 03-02-2015, 05:17 PM
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Bob -

Thank you for the advice! I am in absolute agreeance with you under the condition that the owner actually cares about their TV. This was given to me for free, placed in the recesses of a basement and never used due to the terrible picture quality.

I only decided to work on it when my wife wanted it out of the basement and a cheapo $200 lcd instead. I'm strictly working on it for the enjoyment of learning about something and maybe for the sense of satisfaction that comes from repairing something. I also may be so physically weak and lazy that I'd rather try to fix it than even contemplate hauling it up the stairs.

I went into this with eyes wide open that at any moment, I would quite possibly electrocute myself or destroy the TV.

If this was a high definition set or something that I had an attachment to, I'd absolutely send the board out. I don't think I could give away a 1995 model year standard definition RPTV though.

So rest assured, I'm not so full of hubris that I assume I have a skillset even approaching that of a career technician. I'm the first to admit that I don't know what I'm doing, but I am having fun doing it, and that's what is important to me.
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post #12908 of 12908 Old Today, 11:20 AM
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Thumbs up Pioneer SD-P5181-K Pincushion - Solved, HV circuit

Well I fixed the set last night.

I spent a few hours over the weekend reading posts from an old TechAssist mailing list, hosted at freelists. I really recommend anyone with a TV problem take a look at those, there is a ton of valuable information from experienced techs in those threads.

The pincushion problem, to my understanding, comes from insufficient voltage from the HV circuit. On this set, there is no separate pincushion circuit - the HV controls horizontal and vertical, and everything else follows the green circuit on the convergence board. This is why the horizontal adjustment on the power board and the green vertical and horizontal trimpots on the convergence board were not working properly. My convergence board was fine, everything was coming from a problem with that HV circuit on the power board.

I pulled the power board and went over every single solder joint, looking for bridges. I use some magnifying loupes with a light for this, but I also recommend changing the lighting sometimes. Occasionally if the light you're using is too bright, you'll wash out everything and you can miss a tiny bridge. I also use these plastic tools from some cheap-o soldering tool kit that Radioshack sells. I run the plastic tips around every joint to make sure there isn't some little strand of solder I'm missing. It also helps you locate traces and copper rings that might be coming up from the board.

On the high voltage circuit, I had reflowed everything with the exception of maybe 5 or 6 solder joints that I had skipped because they looked great and were partially underneath some adhesive material. There is no way those little joints were the problem, I had thought... but I used an exacto blade, cut away some of the adhesive, and reflowed them.

Of course, that was the problem. It fired right up, I did a quick user menu convergence alignment, and went to bed. Now it's time to try calibrating with the Avia disc!

So, a few words of advice to anyone with an old Pioneer (but I think this actually applies to almost any old set) - here is what I would do if I had this problem again with another set:

1) Reflow the entire power board, right away, 1st thing, regardless of whatever else I might think is going on. Go slowly, and get EVERY SINGLE JOINT, even if they look good and you think there's no way it's going to be related to the problem. The ones you skip will inevitably be the problem. I think Pioneer used approximately as much solder on the entire board as I used on maybe 3 joints. Everyone talking about their horrible factory soldering is underestimating the problem, if anything. It's not exaggerated.

2) Be careful when reflowing and adding solder to the big joints for the transformers and transistors. The first time I did it, it was very late at night, and I felt like I had added a lot of solder to a joint that wasn't looking any fatter or plumper. Well, it wasn't, because it was running down on the other side of the board on the transistor wire. If I hadn't caught that I'm sure it would have shorted and done something fun like burned down the entire house, or exposed me to 70 gray of radiation when I plugged it in.

3) On the convergence board I think I only needed to change the convergence amp, the big 220uF electrolytic caps right next to it, and the piggybacked resistor. I had fun replacing all the other crap, but if you're actually trying to solve a problem and not just hiding from your family, you should focus on the convergence amp and the big resistors right next to it (3W 6.8OHM, 3W 10OHM + 3W 22OHM piggyback on this set).

4) Take a look at the two big raised resistors in sequence on the power board right next to the 3 HV connectors for the CRT boards. They had burned the PCB on mine.

Thank you to everyone who posted in this thread and similar ones on other forums. This was a really fun project for me and while the TVs themselves may not be worth much, it's a very satisfying feeling to bring them back to life.
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convergence , Panasonic Tc P65v10 65 Inch 1080p Plasma Hdtv , Pioneer Elite , pioneer sd-p5181-k , Plasma Hdtv
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