Fine tuning a projection TV's color?

[jeffgothro]

I'm buying a 50" projection TV off craigs list for next to nothing - guy says it has a slight color issue (I will find out how slight later when I see it - could be nothing, or nothing I cant live with - I dont know yet) but other then that its in tip-top shape as I understand it.

Now, I've opened up a few analog/standard TV's and if memory serves me correctly there is usually some kind of fine tuning screws/knobs for color adjustment (besides the color adjustment knobs outside the TV) that are inside the TV that can be played with. I dont know anything about projection TV's this will be my first, can someone tell me if there are any sort of fine tuning (tuners) that can adjust the color from withinside the projection TV itself? I beleive the guy told me its a magnavox brand TV.

 

[bandphan]

here is a good starter thread for RPTV dyi repair

http://www.hometheatershack.com/forums/service-support/5600-crt-based-rptv-convergence-repairs.html

 

[jeffgothro]

Thanks, I'll check that out.

 

[yettitheman]

If it's a CRT projection TV, great news; they are relatively simple to work on, repair, and will (hopefully) last quite a while.

It's possible that the coolant just needs changing; common on CRT RPT's with a lot of on time. Or the gain has slowly drifted.... but I'd say by looking afar at the age of the set, that it's a bit old and need's the coolant changed (if it's changable).

BIG thing to think about is high voltage; unlike a tube tv which has P2 high voltage on the tube as well as the transformer and caps, you have 3 P2's on CRT projectors, as well as corresponing transformers, power distribution blocks, and the caps that go with them as well. LOT'S of high voltage going on in there. Excercise extreme caution when working on it with live power (and even when it's off and unplugged; CRT's have a tendancy to couple a charge for quite a while, even after the set has been unplugged).

If you don't know how to ground out the high voltage P2 on the tube, you really shouldn't mess around in the set. However, if you do, I'm not responsible for any injury or liability that may occur if you start messing around with the TV.

I know on my Sony projector, there were color gain and focus for the gun and yoke. You probably wont have focus as your distance is fixed (mirror that is in the back of the TV). But gain will probably be there, as well as OSD tint, and RGB bias.

So... either the coolant is bad and needs changing or the tube/s are burned in. I know offset adjustments can drift over time, but too much is a sign of a bigger, and sometimes more obvious problem.

 

[jeffgothro]

Well, I got the TV home - the picture seems a little blurry, or like the people on the screen have a slight halo around there bodys, not to bad, but noticeable, there are also a few faint yellow blotches towards the middle of the sceeen...I'm thinking the display may be damaged. In any case, I'm probably wont work on it as of I know thats beyond my expertise (If it can be fixed for 300.00 or less - which I doubt - I may have it serviced) as of now though I'm ok with the TV actually, its far from perfect - but good enough, and besides, I hardly ever watch TV anyway and only payed 40$ for it.

 

[yettitheman]

Well, I got the TV home - the picture seems a little blurry, or like the people on the screen have a slight halo around there bodys, not to bad, but noticeable, there are also a few faint yellow blotches towards the middle of the sceeen...I'm thinking the display may be damaged. In any case, I'm probably wont work on it as of I know thats beyond my expertise (If it can be fixed for 300.00 or less - which I doubt - I may have it serviced) as of now though I'm ok with the TV actually, its far from perfect - but good enough, and besides, I hardly ever watch TV anyway and only payed 40$ for it.

Well... if you ever think about messing with it, it'll look something similar to my Sony Projector listed here:
http://forums.audioholics.com/forums/showthread.php?t=48190

You won't have nearly as many adjustments or parts, but there is still quite a bit going on in a CRT RPT.

 

[Milo Toll]

hmmm

I seem to have a few spare parts

 

[just-some-guy]

clean the screen, inside and out. also clean the mirror and the CRT's.

 

[jeffgothro]

Well, here is what the picture looks like...not great, but good enough, its pretty old TV I think and also it looks better in person, the pics dont really look good, not sure if its the flash or the lights in my room were on or what. But hey, it was 40$, I wasnt expecting HD or nothin...lol I may upgrade it eventually...I see these things all the time...CHEAP! Everyone wants new wall mount TV's and HD sets nowadays.

Right now I have it hooked up to my NAD receiver and Acculine A3's, it sounds good, nice smooth punchy theater sound. I'm probably going to upgrade to a newer used NAD or Carver receiver.

I've seen two of these (or similar) already sell on ebay for less then 3 bills, and one was new in the box, also saw a SUNFIRE Grand Theater go for almost four bills I think it was.

 

[krystalcleanwin]

Hi I have a magnavox identical to the one you just bought off craigslist. Mine was given to me and I have the same problem as you. The back has been taken off mine and yes there are two sets of fine tuning screws one red one blue and one green and a second set directly underneith the first. Please tell me did you ever figure out how to adjust yours or do you know where to get a manual or what model number it is?????

 

[MatthewB.]

First off you never want to adjust the green (that's the baseline) so deal with the red and blue first to get the best picture before even thinking of adjusting the green. Next clean the lenses and mirror with a lint free cloth (never ever use paper towels or products like windex with ammonia) buy a calibration disc and make sure you do a thorough convergence to get rid of the halo effect (in user setup) to fine tune the picture.

 

[krystalcleanwin]

Okay I'll give that a try but all the colors have already been adjusted. any base ground rules that need to be applied