Mitsubishi RPTV Red CRT Shuts Down-Repair Advice

[ATRON]

First off let me just say thanks to all the Tech guys who have helped people out on this form over the years, your help has been most appreciated.

I'm repairing a Mitsubishi WS-65869 rear projection TV for customer. The customer only brought me the bottom part of the TV and not the top part with the screen and mirrow so as to make transport easier. I'll take it back to their place and then set it up there.

Anyway it had the common problem of the green blinking timer light and no power up. This is the second such TV I've repaired like this so I knew what it needed.

So I replaced the seven bad capacitors in the DM module and unit powered up. Looking down in the 3 lighted lenses everything looked okay for about the first 5 minutes. But then the red CRT went out and the green and blue stayed on. Every time you power it down and back on the red CRT goes out after a few minutes.

Also when the red CRT is on for a short time that it is, when I look down in the lens I can see the menu asking for the clock to be set and so forth. It looks okay for the most but it kind of looks like there may be a vertical height problem? But then again it might be okay I'm not sure, remember I wrote that I don't have the top part and screen, so it's a little hard to tell what I'm looking at? Remember I can see the clock menu find (it's just backwards).

I've tested around on the red CRT board and found nothing wrong. I've repaired a many TVs over the years but always felt like a novice at it as audio and tape decks, VCRs, CD-DVDs, reel to reel, multitrack, obsolete and obscure formats has always been my specialty.

Any suggestions anybody?

And again much thanks in advance

[Village Electronics]

Re: Mitsubishi RPTV Red CRT Shuts Down-Repair Advice

Make sure you have a signal. It will shut off with no signal to the screen to prevent image burn.

[ATRON]

Re: Mitsubishi RPTV Red CRT Shuts Down-Repair Advice

Thanks Village
I understand and even thought of that myself. It is true the TV had no signal when I was testing it and now with the main board out for testing, I wouldn't go back and test that theory just for that reason. Also the last identical model I repaired like this stayed on for about two hours with no signal when I tested it.
But I don't think that's what's happening here because the red and green CRTs stay on? Why would only the red go out?

[Village Electronics]

Re: Mitsubishi RPTV Red CRT Shuts Down-Repair Advice

Thanks Village
I understand and even thought of that myself. It is true the TV had no signal when I was testing it and now with the main board out for testing, I wouldn't go back and test that theory just for that reason. Also the last identical model I repaired like this stayed on for about two hours with no signal when I tested it.
But I don't think that's what's happening here because the red and green CRTs stay on? Why would only the red go out?

If you look down into the lens you can see if any CRT is out or simply muted.
There will be a VITS line or two at the very top (corresponds to the bottom of the projected picture). That will be there regardless of input or OSD status. If the red is out then you start by comparing the 3 tubes voltage wise. You can swap the red with the green sockets* to see if green drive will lite the red tube. You can also see if red drive lites the green tube. At that point logical next steps become apparent.

*I presume you know that means to swap sockets and wiring.

[ATRON]

Re: Mitsubishi RPTV Red CRT Shuts Down-Repair Advice

Village you were right! It was just the screensaver kicking in.
Apparently identical models aren't created the same and all I had to do was just hit a button to bring up any OSD. I just wish now that I had hit a button before, but with no signal and no screen I saw no reason to then. Oh well?

I still think they'd mute all three together. From what I understand it's usually the green CRT that gets weak first, while the red CRT usually is the last one to be replaced. If they'd mute just any single one CRT first, I figured it would be the green one would it not?

Thanks a million Villagefor the advice and thumbs down to me for not following my instincts!