RCA P52937 (PTK195) unusual convergence issue

[PTKmoron]

I have a strange convergence issue with my old 2002 RCA big screen, Does anybody out there who tinkers with the older CRT big screens have any info on the convergence power supply board (number POWR-530), or the Digital Convergence Main Board (either DIGI-970 or DIGI-980) for a 2002 RCA p52937 with chassis PTK195M4B?

I know about the convergence power supply board usually going first, but the thing is, I have the advance convergence menu still, and its only the left side of the picture thats bowed/off slightly. Its adjustable to perfection on the entire screen, even where its bowed except for a 5x12 spot on the screen where blue and red lines make a crazy swirling net shape that doesnt move. In the included pics, its all that stuff over the patriots logo, and the words below are supposed to be white. You can really see the bad spot when in the advance menu, as i have included pics of the screen in both red and blue adjustment modes.

I am wondering if since my convergence power board still shows voltage on all 5 output wires that are supposed to have, if its just the convergence main board thats shot, and not the power supply. I can unplug the input power from the PSB and it makes the screen look completely HORRIBLE, and the advance convergence menu is no longer available like this. Also the wild spot on the screen is not there with the psb unplugged (it looks horrible but you can tell the odd bad spot isnt there anymore.

I have only seen one other pic on an online thread of a ptk195 chassis tv screen with my issue, and interestingly enough, its in almost the same spot on the screen as well. Everybody giving info on what to test was up in arms as to whether it was the PSB or the mainboard, and it ended with everybody agreeing on replacing both boards to be safe. I can get both now from ebay, but I dont want to shell out (and take out of circulation) a part that I dont really need.

As mentioned, the output voltages on the psb are about 2-3 volts higher on the first two pins that have to be read with the meter probes reversed (its a negative vdc reading), and the other 3 pins past the chassis ground pin read about 2 volts lower than whats specified, but I have been told that its close enough to be in spec still. I am no expert in that regard, and am not sure if the voltages should be dead-on, or within a given amount. All I know is the peoples experiences that I have followed who needed just the psb have always had a very low or no voltage situation on one or more of the output pins that are supposed to be hot. They also lost the customer advance convergence menu (or if it remained, they couldn't get any of the colors to remotely converge, it was totally off). I still have all of the previous, with no other symptoms or misbehavior from the tv itself as a whole.

Thanks in advance for any insight or info at all,

Bob.


MORE INFO: I just swapped the connectors for the yokes on the convergence board. Even though it distorts the screen from where the guns are on different rack positions, when swapping the red with the blue yoke you can tell the red lines take on the odd warped distortion pattern of what the blue was doing previous to the swap in the spot thats screwed up. Hopefully its just the convergence board, and not the convergence psb or the flyback.

[Mrx3750]

Re: RCA P52937 (PTK195) unusual convergence issue

Seems like you have a convergence IC that's just starting to go. Or you have a resistor that's failed.

Those IC's, usually labeled STK-something or other control convergence across the screen, which is divided into sections. Looks like one of those sections has either failed or is not getting power.

Step 1 would be to remove the board that the convergence IC's are on.

Step 2 is examine and test all the resistors that feed the convergence IC's.

Step 3 may involve replacing both IC's, the resistors that feed them, and any pico fuses, if there are any.

[PTKmoron]

Re: RCA P52937 (PTK195) unusual convergence issue

Thanks for the quick reply, I did a thorough inspection of both the convergence main board and psb, top and bottom and everything looked good visually. I just went ahead and ordered an entire used refurb and tested convergence main board for it, $70 off ebay from a reputable dealer. I am hoping that the convergence psb is ok, since it seems to check out with a voltage test on the outputs to the convergence board.

I felt around the transistors after the tv had been on for awhile, and it has six heatsinks on the convergence main board and some of them only have 2 transistors per heatsink, and others 4. Some of the 2 transistor heatsinks are running hotter than the 4 transistor ones. Odd to me, seems like it should be the other way around. .

Anyways, wish me luck, the new board is supposed to be here friday. Ill post results, just to finalize the thread since my problem is specifically unusual, whereas most have alot more "3d" showing in the screen when they have issues with the only stk transistor on the convergence psb, and they found it by probing the outputs and finding the voltages non existent, or pathetically low, like 2.34 vdc on one of the wires when its supposed to be 45 vdc.

[PTKmoron]

Re: RCA P52937 (PTK195) unusual convergence issue

I got the convergence main board a day earlier than expected. It didn't help with the fish-eye effect, but it cleared the odd swirl of color lines i had developed. I am actually thinking my convergence power board is flaky.



I have read alot and researched, and it turns out my ptk195 tv(s, plural since two days ago) both have the newer convergence power supply "that uses discreet components in place of the usual STK IC"...




That's what has gotten me very confused, I have been told multiple, multiple times that with my symptoms, the STK-730 was bad on the power supply and it needs replacement. No offense to anyone, but it had me seriously thinking wtf, I see no STK IC anywhere on this board, am I losing it???! (lol). My power board has a single, much smaller mosfet transistor #246967 on a heatsink where everybody says that stk ic is supposed to be (location Q19701)


Since this board does not have the STK IC power board, maybe its possible with the #246967 mosfet transistor version that its output voltages are out of spec just enough to throw the convergence way off, but not enough for the tv to dismiss and bypass the convergence circuit on startup thus removing the convergence adjustment menus.


I have been repeatedly told that "if you go into the screen menu,
and you have both the basic and advanced convergence adjustment menus missing, the STK-730 on the convergence psb is faulty; check output voltages against spec, and replace if out". That info is obviously for the older psb (i think chassis ptk195AB had these boards factory).




I am sorry for sounding really dumb here, I don't know the ways this #246967 mosfet transistor fails, and how it would effect the output voltages to the convergence main board (would voltage go up, down, be non-existant/dead or close to spec until under load, etc?).



I am doing the shotgun approach, I am getting in-spec power from the big main power supply board for the entire tv to the convergence power supply board, after that point to the convergence main board is where the voltages start getting a little wild. I thought the output voltages from the psb were close to spec, but I rechecked them and three of 5 outputs are AT LEAST 3 volts higher than spec, and the other two are about 7-10 volts higher. One of the three that are around 5v high out of spec are read as -vdc readings.


So to that, I have already ordered the only good PTK195 POWR-530 psb I could find online awhile ago, and it should be here tuesday. I will still update this, even if i end up losing to the problem. Maybe it will help somebody else, through my research I have followed alot of people who were in the same situation as me, but they usually only tried another convergence main board, or just their psb when it had the #246967 mosfet transistor, never both at the same time. On a side note, most who verified they had the stk-730 ic power board got the convergence problem fixed once the psb or stk ic itself was replaced.


Wish me luck lol, Im gonna need it!

[PTKmoron]

Re: RCA P52937 (PTK195) unusual convergence issue

Well i lost, I got the power supply, and it made no difference, BUT I did manage to fix the pincushion problem (along with bad news about my convergence boards and the one i got off ebay...) It turns out the pincushion problem I had was a bad MUR460 diode and a solder break down from the diode in the pin amp circuit on the main deflection board. I put a new diode in, fixed the solder break and now the screen is square, but I realize now that I have had other issues I didnt know about previously.

I have 3 separate convergence boards now counting the ebay board, all exactly the same and failed the same except for one difference. I have swirls of blue and red with all 3 boards like what is shown in the first pics from my OP, except the spot(s) are in different areas of the screen with each board.

As I was adjusting one of the sets' convergence, suddenly another spot of convergence let go and left another wild tangle of lines on the screen. I heard absolutely no noise when this happened, so I assume the vertical transistors stopped switching in all 3 of the vertical color circuits at once, or at least partially.

Does anybody know if the 3 vertical circuits share a common transistor or something of that nature? I find it odd that all 3 colors came out of convergence all at once and in almost the same pattern that last time. If not, Ill have to see if one of the television board r&r companies can rebuild one of my boards to new condition. It may not be worth it to some people, but I would rather spend $300 to rebuild my current tv vs buying an new one.

[PTKmoron]

Re: RCA P52937 (PTK195) unusual convergence issue

Well I feel like an idiot now. I have figured out what causes those spots I had showing on my displays...

For some reason, the convergence memory chip on each board fragged out for a split second, and lost the setting for those particular spots as I was adjusting the convergence, resulting in a birds nest of blue and red lines on the screen concentrated in one spot. I was able to adjust and "straighten" the wavy lines back out with the customer convergence menu.

It took around an hour and a half each set, due to the entire blue and red grids having to be pulled back straight. There was some tough spots that I didnt realize where the lines were actually pulled up, overlapped and folded in the opposite direction.

The only catch is, if the green has moved or went wild, theres no way to fine-tune/adjust it back, so I am SOL in one small spot on the 52" chassis. The blue and red distortion is gone though. It will do for now, the 61" is my choice of boxes to use anyways, so the board with the green distorted spot will stay in the 52". I tried the ebay board again just to check, and it still acts like its not compatible , or was malfunctional upon arrival (it never worked right imo). I am not gonna hold anything at all against the seller, as I needed a good core to send off to moduslink for rebuilding anyways. I know the nature of these old board things, and the power supply I got from him is working great so at least I feel like I broke even, with both tvs functional now (for the most part lol).

Thats about it for now, I am ahead 1 power supply and a fixed pincushion circuit on the 61", and I got 90% of the convergence lines off my 52", which is why I ended up buying the malfunctioning ebay board, and picking up the 61" for free as a parts tv.

[PTKmoron]

Re: RCA P52937 (PTK195) unusual convergence issue

I figured it out finally, its the eeprom on the convergence board in the rfi box that causes the bowed top and bottom of the screen, 24wc16p, location U19500. Its memory is either corrupted somehow, or the eeprom is getting weak as i can swap it and no matter the board, the same display is rendered from the board the eeprom came from originally.


It anybody knows about eeproms, can i just order a new one and install it and go, or is it mandatory to have the chipper check interface to initialize it for the tv? I havent a clue about this, if whether the tv will initallize a fresh eeprom and start writing convergence data to it, or if I will need to "format" the eeprom for the tv to recognize it???