blue gun is out on pt47wx51e

**ZachGTI** · **02-23-09, 06:50 PM**

ok so, thanks in advance for all your help. i have done hours upon hours of exhaustive searches... i got this tv from a friend when i got it, it had large blue arch running thru the lower middle half of the screen. before doing enough research i found someone who said if you play with the convergence knobs that it will go away, so thats what i did, i only turned the blue down (as in not alot of blue hue in the picture) and i kept playing with it because i wanted a perfect picture, well sometimes when turned it back up or intensified the blue the arch would come back and the blue convergence would be real sloppy, so the last i fooled with it the blue went out all together. and thats that. so ive been living with this rear projection crt tv with only red and green guns... argh anyway i refuse to believe that the gun is actually blown, and im not paying 300 bones to get it fixed. ive found through this site the acceptable place of getting new IC chips and ive found them on ebay, i have a buddy who is really good with fine point soldering, im that good with super small stuff, the original part number is the infamous stk392-110 and panasonic has some odd replacement named C5AA00000203. but could this really be my problem? hmmm i live in CT, the tv was manufactured in 2002.

**lcaillo** · **02-23-09, 08:22 PM**

Convergence ICs would not cause the blue to be out completely. It would cause it to be out of convergence or the set to shut down.

Please, do not buy your parts on Ebay. You can get them from several reliable suppliers like Acme or B&D and be sure to be getting first quality parts.

**ZachGTI** · **02-23-09, 08:49 PM**

ok so what do you think the problem could be?

**lcaillo** · **02-23-09, 09:24 PM**

It is hard to say without doing some troubleshooting. Is the filament lit on the blue tube? Connections intact? Do you get nothing when turning it up all the way? I assume that you were adjusting the screen control, is this correct?

**ZachGTI** · **02-24-09, 10:28 AM**

yes the little orange filament is lit on the bottom part and nothing happens at all when i turn it all the way up. correct, i adjusted the screen controls not the focus controls. i think thats what they're called, as far connections go, i looked and all seems well but that would have to be a pretty big coincidence that at the same time i played with it a connection went bad or maybe i blew one of the hundreds of resistors, i dunno....????

**lcaillo** · **02-24-09, 11:23 AM**

This will require troubleshooting. There are no shortcuts. If you can trace signals and understand CRT bias and drive concepts, and the safety considerations, get out your scope and meter and track down the blue. If not, you will need to have a professional evaluate the set.

**ljryjj** · **02-24-09, 02:21 PM**

Hi lcaillo,

Would it be safe to just unplug the blue sub-yoke for convergence? If yes I would recommend this experiment and see if blue comes back. Worst case an experiment can be done by pulling the two STKs out and see if blue comes back.

I don't think it's a bad blue crt. Could be too much bias current added by defective blue channel in the STK IC.

**lcaillo** · **02-24-09, 02:34 PM**

Once again, the convergence circuits have nothing to do with no blue. The only way that this could be the cause of your problem is if the convergence was so shifted to push the raster off the phosphor. If that was the case you would likely have a cracked tube from overheating or would still see a glow. If you disconnect the convergence yoke with the ICs installed you will cause the resistors to take the full load from the amps and quickly smoke them. If the ICs are not installed there is no signal flowing through the convergence yokes so it would make no difference to disconnect them.

If the filament is lit and the CRT is dark, you need to figure out why. This takes troubleshooting the CRT bias and drive circuits and perhaps the video path.

**ljryjj** · **02-24-09, 02:43 PM**

don't know why, but I did see no green with my SONY RPTV. It had a blown fuse. When I put a fuse in and fire the set up, green was gone, and four 4.8ohm resistors smoked(sad experience

). That fuse from radioshack didn't blow. TV is fixed with a new set of STKs and resistors and green is back.

**lcaillo** · **02-24-09, 02:50 PM**

The significant part is "don't know why." I explained the only condition that could cause a single CRT to not produce an image due to a convergence failure. Perhaps the defelction was so great that you could not see the image, perhaps something else was going on that you are not aware of. We don't know. Regardless, the information provided remains the same.

**ljryjj** · **02-24-09, 02:58 PM**

I couldn't be wrong in telling which color was missing,

My KP-53s25 has most of the menu items in green. When green was missing, it was only dark black there instead.

Just a data point,

**lcaillo** · **02-24-09, 03:25 PM**

Look, data is no good in the absense of context. There is obviously more at play here that we do not have complete information on. I have given you my experience on the matter. There is little that intereacts between the presence of video on a single tube and convergence outputs other than the case I described, which is extreme and dangerous. If you have some specific explanation of how what you describe might occur, I will happily stand corrected. Simply stating an experience without an explanation does nothing to inform others about anything more than that you don't know why it happened. There are lots of coincidental possibilities that could explain the experience. I know of no technical explanations other than the one that I proposed. The point is, if you have a CRT that does not show an image, you likely either have a very dangerous and extreme defelction of the beam that can easily crack a tube, or you have something else going on besides a convergence related problem.

**ZachGTI** · **02-24-09, 05:17 PM**

thank you sir, so i suppuse im gonna get a professional... they quoted me 100-200 to bring it in if its the convergence ICs, and 200-300 for a house to do the same. do you think, ROUGHLY about the same for whatever could be causing this. i think you nailed it on the head with:

Quote:

The only way that this could be the cause of your problem is if the convergence was so shifted to push the raster off the phosphor.

i believe i slipped when adjusting and perhaps moved the knob too quickly... a few adjustments and 10 min later, no blue.

**lcaillo** · **02-24-09, 05:26 PM**

If you turned the screen control down all the way, you would get none of that color. If you turn it up and don't see that color, something is broken that will require troubleshooting and is unlikely to relate to convergence.

**ZachGTI** · **02-24-09, 05:37 PM**

ok cool looks like im in the doghouse on this argh.

**ljryjj** · **02-25-09, 10:54 AM**

Hi lcaillo,

I agree with you. I would like to delve into EM theory for this but that would be a luxury for me. Just went through and survived a layoff yesterday. But a friend of mine is not so luck. I'm feeling really bad.

Well back to the topic. Simply put, blue is gone after playing around with blue convergence. I can't say there's no correlation. Convergence is all about deflection anyway and I did see green was gone in my TV. If this were my TV I would take out the two STK ICs and see what happens to the blue. The gen of trouble-shooting is to narrow the scope till pinpoint the culprit.

take STK out
if (blue is back) {
sth wrong in STK or related;
} else {
something else with the CRT
}

If a CRT is cracked I expect to hear hissing noise or see blue arcs in the dark.
I'll be very interested to see what's with this TV, :-)

Disclaimer: I'm not a service professional though I have 12+ years of experience in fixing CRT TV/monitors mostly helping friends/neighbors. I'm trying to be helpful but you should take lcaillo the guru's opinion over mine, and I presume you have soldering skills and you understand what I'm talking about :-)

**ZachGTI** · **02-25-09, 04:18 PM**

hmm ill try that, however when there is black on the screen it shows up black when im waiting at an input screen there is red and green hues to it....

**ljryjj** · **02-26-09, 12:49 AM**

that's normal. Black means no red/blue/green at all. White means mix of equal amount of red/blue/green. If blue is missing a white picture shows up as yellow.

**ZachGTI** · **02-26-09, 01:00 PM**

yes hahaha exactly, it looks like im looking thru a bottle of mountain dew

**ljryjj** · **02-28-09, 10:41 AM**

Hi ZachGTI,

There may be a quick experiment that you should be able to try.

Well if you take off the speaker grille of your TV and possibly another blank cover, you should see a focus block like this:
http://1.bp.blogspot.com/_0xPnZbi2Qt...adjustment.jpg

There are two rows of knobs. One row to adjust focus and one row to adjust screen voltage.
Figure out which one is for blue screen voltage and turn it with a screw drive bit by bit SLOWLY when TV is on. It's simply a test to see if you blue CRT is functioning and if there's a problem with blue screen voltage or blue deflection. Make sure the knob goes to the original position when you are done.

Hi lcaillo, what do you think? :-)

**lcaillo** · **02-28-09, 03:37 PM**

He said that he was adjusting it when it went out. From his description in the first post it seemed that it was the screen control that he was adjusting.

**ljryjj** · **02-28-09, 04:15 PM**

Aha, he did say "knob" in his post,

Well nothing to do with convergence then. The blue arcs he mention could be simply retrace line then due to blue CRT etc aging, and he could have turned down screen control too much,

We'll see

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