1. Home
  2. Electronics Repair
  3. Rear projection "cracked" red gun

Rear projection "cracked" red gun

I have a 52" Hitachi rear projection HDTV. The red gun was too hot and throwing off the colors of the display, so I opened up the bottom of the cabinet to see if there was anything that could be adjusted/ cleaned up to try and correct the color. I found a series of knobs that adjust the intensity and focus of each crt, and began to test the sensitivity of the knob and how much they needed to be turned to acheive a certain amount of adjustment. Apparently I turned the red gun up way too high and the display turned off. I turned the red back down, turned the tv back on, and now have what appears to be a "crack" at the top of the red gun. I am not sure if this is in a lens, or a coating, or the crt itself. I was wondering if anyone could take a look at these pictures and advise me what the issue is.

formatting link
formatting link
formatting link
formatting link
formatting link
formatting link
formatting link

Reply to
N|A-Orion
Loading thread data ...

Have you looked down into the projector tube through the lens with a flashlight and noticed anything odd looking? Stuff like that usually shows up pretty easily and you can have a good look down in the tube through the lens if the fluid isn't too cloudy. I've looked in mine after cleaning and a repair and noticed fibers or even hairs in the fluid right from the factory. These are magnified by the lens but otherwise too small to appear on the screen.

Reply to
Meat Plow

I'd have to pull the screen to look at it from that angle, and I'm selling the tv so I don't really want to go through the hassle. I'm selling to a co-worker, so I'm really mainly looking for a "what to expect" From what I can tell they are just going to have to deal with the discoloration which they don't mind for the price they got. I'm just making sure something more serious is not going to come from this and have her breaking my door down :)

Reply to
N|A-Orion

Well, the tube is certainly not cracked - it wouldn't work if it were.

Reply to
Jumpster Jiver

You burned the line into the phosphor of the red crt by turning up the red drive too high. I remember seeing a Hitachi service bulletin out to put with the adjustment manual warning not to do exactly what you just did.

The set would go into protect shutdown when the drive was too high. The shutdown would collapse the horizontal drive, but the drive was so high on the red that it was at so high a level it was still driving the tube when ti collapsed.

The mark will never go away.

One of the other tech's where I worked did exactly what you did by accident. The tube had to be replaced.

formatting link

Reply to
dakdak

It looks like you burned the phosphor, the tube isn't cracked but it may as well be. It looks like there was a momentary loss of deflection, perhaps a poorly designed protection circuit didn't kill the beam before shutting down the horizontal deflection.

Reply to
James Sweet

Well it's possible you've caused some damage that will come back to haunt you.

Reply to
Meat Plow

Samsung had this protection problem IIRC.

Reply to
Meat Plow

So if it's burned phospor, is it as harmless as screen burn in? The person who now has the TV does not mind the line, I just want to make sure that nothing else is going to break down the line b/c of this issue.

Reply to
N|A-Orion

Screen burn and burned phosphor are one and the same, yes, it's harmless, just ugly.

Reply to
James Sweet

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.