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Discussion Starter · #1 ·
Hey all,


This is my first post here, so please bare with me. I did do a search, but perhaps my newbie-ness lead to a lack of having the ability to use the right terms and jargon to return any results.


Here is the deal. I just acquired a 2000 Panasonic PT-56WXF95A RPTV. The owner said the green tube was out. When I got there he further explained that the TV wouldnt turn on (i assume he meant there was no picture), that is unless he unplugged the PCB from the green tube. Then the TV would turn on, but obviously be all red, blue, and purple. The unit was in his unfinished basement, with no outlets in sight.


I just got home with the set not too long ago, and have been all over the internet trying to do research. I am a very tech savvy/DIY guy, and have built/repaired everything from mobile dj rigs, computers, car and home audio, arcade machines/cabinets, cars, motorcycles, just about anything I can get my hands on to tinker with and learn.


I was hoping this forum would be helpful in my quest to learn more about the technology and help me to repair this once beautiful set. Yes, I have read that this stuff is not for the faint of heart, and is best left to professionals. However, I really dont have a pot to piss in, let alone several hundred dollars to have someone repair this unit. There are a lot of things that are "best left to professionals" that I have tackled in the past and I hope this can be one more of those items.


True to his word, the green tube board has been disconnected, and the set does power on and display snow as I have no signal connected to it at this time. The unit is in my garage. Getting the menu up shows me all reds and blues, no green. However, the menu flickers and jumps quite a bit and is quite dim as one would expect with one bulb completely disconnected.


Where do I go from here? I downloaded the user manual, but its kinda worthless. I cannot seem to locate a downloadable service manual for the set either. Furthermore, I seem to be unable to locate prices for the tubes on the intarweb, at least for this old of a model from Panisonic. What is the best place to source new bulbs and what should I expect to pay? I read that I should plan on replacing them all as I will not get the right color balance with one new bulb and two older bulbs. Is this correct?
 

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Discussion Starter · #2 ·
update... the menu is no longer jumping. I connected a set of rabbit ear to it just to try the picture out.. reception is garbage, but the set works, just very red and blue with a lot of static.


EDIT: is there a possibility that it is the PCB on the green tube? I read some other posts where that was an issue. They said they had some cold solder problems, and diagnosed it by swapping one of the board from the other tubes. The issue is that last I noticed when I had it open, the red and blue boards were smaller than the green board



EDIT/UPDATE: I plugged in the controller board to the green tube... the entire screen was green when I plugged the unit back in and turned it on. Then it shut off. I did it again, this time watching it from the back and ONLY the green tube was lit. Now I am pretty confused. The green tube is good if its coming on like that, correct?


edit #3: just in case anyone else ends up coming up with this post in a future search or in case anyone is following this thread. I did some more searching and a user with a different brand of rptv had a somewhat simalar issue. It was due to the green tube shorting out and drawing all the power, leaving none for the other two tubes. I would still like to eliminate the possibility of it being the PCB board, I am just not sure the boards will just swap out.
 

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Discussion Starter · #3 ·
well i can swap out the boards as the green board has different connections than the other two...


where does one source the tubes? I found a place to pay and download the service manual, but I cannot find a replacement tube anywhere (on the internet anyways)
 

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VERY NICE TV (check my signature)...


First try adjusting G2 (screen control). Each crt has a control for focus and screen, look for the six knobs. The focus block is mounted on the front of the chasis.



It probably is some kind of failure of the green crt or the crt driver board. As a test you can temporarily swap the boards if you can make the wires reach. The boards do look a little different, but if it were me I would try it.


As far as parts... I just check andrewselectronics.com and can't come up with any part numbers at all. You might have to call them. You may have to send the board and/or crt out for repair since they are probably not available. Here's some sources:
www.videodisplayprojection.com
www.ptscorp.com


You could try the old old Yahoo Group to see if anyone has any spare parts: http://finance.groups.yahoo.com/grou...onicPT56WXF95/


If you get this set working you will love it til death. Still the best picture quality of any Tv I've come accross to this day.
 

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Discussion Starter · #5 ·
thanks for the repsonse!


I guess I will try swapping the board to eliminate that as the culprit. The green board serves as the main link, all the wires connect to it, then chain out to the other two boards. I guess its like you said, if I can make the wires reach I should try swapping them around.
 

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Discussion Starter · #6 ·
Question: Can I just take the middle (green) board, and connect it to the red or blue bulbs without disconnecting any of the wires? Since that board is meant to control green, it wont tweak anything out by swapping it, it will simply make the red or blue bulb display the images that should be green, correct?
 

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Discussion Starter · #7 ·
UPDATE: I plugged the red board into the green tube... green is working. So, that points to the board, right? The green board serves as the distribution board for the other two. If I pay for the service manual, will it have schematics for this board so I could repair it? I dont think I will have much luck finding a replacement
 

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Discussion Starter · #8 ·
well I labeled all the harnesses and wires, and pulled the board. The main capacitor has some of the insulation of the resistor right next to it melted on. I could either remove and replace the resistor and the capacitor, or replace the board. The capacitor and resistor would only be a couple bucks at most. I found the board for 55 bucks plus shipping, but they are not able to tell me if its an item that is no longer available until they place the order with the supplier.
 

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It could also be that you're not getting green drive/signal from the "main signal" board. Like you pointed out the green board -"serves as the main link, all the wires connect to it, then chain out to the other two boards". So you really need to turn it on with a signal connected then take voltage measurements on those pins of that 8-10pin connector. They should be "paired" ground+signal for each r/g/b. Probably less than 5vdc. If the red and blue have good voltage but the green doesn't then you have a problem with the output of the signal board not the green driver board. If you get similar voltages for r/g/b then the drive is ok and you do have a crt driver board problem. Try not to touch anything else in there! Some very high voltages on those crt driver boards!
 

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Discussion Starter · #10 ·
that confuses me....


when the board was connected to the green tube, it made teh entire screen go really bright green, then the set shut off. Seems like I was getting a green drive/signal if it was doing that, right? I am not at home anymore, doing a POS system installation and setup for my aunt and uncles resturant. If I remember correctly, there are two 8-10 connectors on the front of the board, going out to the red and blue tubes. There is one more of those connections towards the back of the board coming from the mainboard in the back of the set. I'll take a look when I get back home tomorrow or tuesday and see if I can tell which pins and headers you are saying to test.


if I get the service manual, does it have schematics for the pins/headers/ and boards?
 

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Quote:
Originally Posted by DigitalFusion /forum/post/12881636


....when the board was connected to the green tube, it made teh entire screen go really bright green, then the set shut off. Seems like I was getting a green drive/signal if it was doing that, right?

Nope. The symptom you describe sounds exactly what happens if you loose green drive/signal from the main signal board. Service manuals are good to have, but very cryptic and not made for beginners. It will give you schematics, but not what voltage you should see or even what connector does what, etc.
 

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Discussion Starter · #12 ·
hmm... thats not what I wanted hear!


So, if I am not getting drive/signal for green from the main board (say I test the wires and they are not consistant and much higher or lower than the blue/red) then I have to replace the main signal board or is there further tests I could try? I guess thats getting a lil ahead of myself.
 

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Ya, pretty much sums it up...
 

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Discussion Starter · #14 ·
i can test the leads without the green board in there cant i? The leads coming into the board fromt eh main baord? I dont think I can get my hands and the leads in there to test with the board connected and installed


another thought: Doesnt this melting kinda point to this board (green crt board) being the cause? I suppose its possible that it is an effect tho. :Shrug:
 

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Yes, you can test it with the green disconnected. The resistor/cap is hard to comment on.
 

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Discussion Starter · #16 ·
hmm, I left the green board out and tried to test teh leads, when I plugged the power back in, and turned the set on, there was this strange rapid clicking sound, so I turned it off right away. I then installed the green board, but left it disconnected from the green crt and powered it back on. Now, I only get the red images on the screen. The faint light on the bottom of the tubes is burning on both the red and blue, but blue is not projecting. I quadruple checked all my connections, making sure everything was tight and connected correctly before I even turned the set on. Then I checked them several more times after I turned the set on and was not getting blue.


I decided to start testing leads at that point. I tested both the high voltage and low voltage pairs for each board while the set was on, playing a DVD (only red colors as the blue was still not projecting, and the green crt was not connected to the board.


LG1, the main connection going to the green CRT board from behind:
  • 1st Pair-GREEN- (LG1 pin 1&2) = 10.3V
  • 2nd Pair -RED- (LG1 pin 8&9) = 11.6V
  • 3rd Pair -BLUE- (LG1 pin 10&11) = 11.7

I tested the pairs going out to the red and blue boards:
  • Red = 2.81V
  • Blue = 2.78V


High Voltage on the focus block going to each tube:
  • Red - 151V
  • Green - 135V
  • Blue - 130V



Does any of this information help? I cannot stress enough how happy I am that you are helping me out and posting here. I literally get up each day and check this forum first to see what you have had to say, and then I do it several more times throughout the day. Thanks in advance again!


BTW - I was thinking maybe I will take a short video of what it is doing, and the tests I have done and whatnot and upload it to my server. Would that be more helpful?





UPDATE: I pulled the back cover off, and had the unit on. I noticed that the blue projector is kinda working. I see no blue colors on the screen, but with the rear cover off I can see that the blue projector is glowing faintly. If I put my hand a few inches over the top of it i can see the blue light glowing on my hand. With all the lights off and the tv on, I can see faint traces of blue in the picture on the screen. I also noticed a two pin header (SG2) just kinda hanging there. I did not disconnect this header. I looked in from the rear of the set, and see on the secondary green crt board that there is a two pin header labeled SG2... is this supposed to be connected? What does it do?



UPDATE 2: I connected the SG2 header back as the service manual shows it connected. Didnt make a difference. I have also had the TV on for a while, and I just noticed the blue is not working at all now. Not sure if this is a time issue, or just that its an intermittent issue with the blue.
 

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That (upper) secondary crt board is just scan velocity modulation for sharpening. Some people disconnect them because they feel it does more harm than good to picture quality.


Sounds like you got a service manual, I guess that's how you know the pinout of conn LG1. The ~1.5v difference on the green could be your problem. Doesn't seem like a lot, but I think that it is an issue. If I get time in the next few days I'll put the meter on mine...


As for the blue... Is there still a glow down in the bottom of the neck down by the crt driver board? You should take the screen off and look down into the lens with signal applied, then use your G2 screen controls turn up the blue slowly, look for it to come on.
 

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Discussion Starter · #18 ·
Yeah, I paid for a download of the service manual, but its a lousy scan of a photocopy and anything that was gray is illegible.


Upper CRT board:

So.. I can ignore these boards for the most part? I was abotu to test the voltages on the headers for those... should I not worry abotu it?


Green:

If you could find the time to throw a meter on yours, I would be INSANELY greatful!!!!!


Blue:

There is still a glow down in the bottom of the neck, just as bright as the red CRT which is working. I could use the screencontrols/focus block to turn it up, but its confusing why that would be the issue considering blue worked fine before.
 

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Discussion Starter · #20 ·
adjusted blue on the block... got it back.. must have bumped the knob when I was taking the green board in and out!


Another note that I never mentioned... the green is all the way down on that, and if I turn it up even the smallest bit with the green CRT connected to the green CRT board, it shuts the set off immediately
 
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