High Def Forum
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CRT Dirty Screens?

11-30-2005, 11:29 AM
Apparantly this is an ongoing problem with Toshiba sets, although it seems to be inherent to all CRTs. When you have a bright white background, you can see what looks like a yellowish haze, particularly around the edges. I noticed this and thought it was a power supply problem. I live in an older house with somewhat suspect wiring. I tried several different outlets, including the stove which is probably the cleanest power. I also am powering through an APC surge supressor which has some power filtering abilities. I created a pure white jpeg card and displayed it at full res with my DVD player. It's pretty noticeable then. Some have described it as looking like the inside of the tube needs to get wiped down, which is pretty much impossible from my understanding. I googled ""Toshiba dirty screen", but didn't get much info from that.
I went back to the store and tried it on their floor model and it was pretty much the same deal. We then tried it on a 34" Sony Wega, and saw more or less the same thing, so what gives? To compare, we tried it again on a Sony LCD, and it was pristine white, no flaws at all.

Does anyone know about this and if there's a fix. It isn't always noticeable, but it's there and it kinda bugs me.

Apart from that, the picture is awesome on my Toshiba 34 hf85, especially in HD. wow! If there isn't a fix, I can probably live with it, but it'd be nice to get rid of it.

11-30-2005, 11:40 AM
The condition described is pretty much what the purity adjustment is there to correct. ISF techs fix this sort of problem all the time as part of their service. It is amazing how many CRTs are sent out with this adjustment out of whack. And to be fair, purity can become maladjusted in shipment as well.

If you want to try this yourself, be careful. You will need to expose the back of the CRT tube where the yoke is located and might be best to get someone to do it for you. You can get instructions by doing a google search on 'CRT purity adjustment', but again BE CAREFUL!!

11-30-2005, 12:05 PM
if you just bought a set use your warranty. i had a tech come out after complaining about the picture and they made a few adjustments. now the picture is alot better.

11-30-2005, 01:35 PM
Thanks, I'll try the tech route first, but will investigate the purity adjustment online for educational purposes.
Thanks again.

12-09-2005, 12:18 PM
The Tech guy came out and degaussed the screen and refocused it. He said the discoloration is common to larger CRT tubes and that it wasn't a problem with purity. Basically there wasn't much he could do about it, or was willing to do is more my suspicion. This discoloration covers a good portion of the screen, but is denser around the edges and the corners. I'm thinking of getting a different tech in to check it out, but just wondering if anyone has any feedback on this first.

12-09-2005, 12:19 PM
forgot to mention that the degaussing and focusing had only negligible results, the discoloration is still there.

12-09-2005, 12:24 PM
Another problem I'm having is when watching HD programming I get a significant amount of flickering, especially in darker scenes and whenever there's a lot of movement. I don't know if this is normal, if it comes from the signal, or is it the set? Any input would be welcome.

12-09-2005, 02:48 PM
i would take the tv back and get another one.that is two many promblems for a new tv.you paid your good money for the tv and you deserve a good picture on your tv.