Question about crts in a RCA Projection TV ppr475t (Chassies model-Hitachi VP6X)

[painkiller64]

Hi, I have this projection tv im cleaning up and well I was looking at each crt inside it (blue,green,red) and I noticed that there is a dirty rectangle stained in the middle of each individual crt. Well I thought that maybe it was the growth in the coolant so i cracked one open, drained the coolant out, wiped down the crt and its still there. Im thinking this is image burn-in but why would it be shaped and colored like that?

Any info would be nice

Thanks, Wes

[N9ZQA]

Wes -

That's just burn-in from the raster displayed on the CRT. The tubes in a projection set get driven harder than a direct-view set in order to get an image through the optics. That tube looks like it's got a few hours on it.

Somewhere there is a web page that shows burn-in patterns of projection CRTs at various levels of use. If the set showed a decent picture before, it shouldn't be too hard to get the same performance again, especially with fresh coolant.

-Jim

[painkiller64]

Thanks for the info Jim, that was exactly what I was looking for. It had a pretty descent picture before... a tad of greenish tint to it but overall pretty good for 20 some years old and free =P .

Hopefully some new coolant should make it look a little better.

1 more question though, that coolant that mcm still sells http://www.mcmelectronics.com/produc...LAID=220229728 , is that ok to use?

[jr_tech]

So, is it fairly common that the long axis of the raster is placed on the short axis of the tube in these sets? The burn pattern is rotated 90 degrees from what I would expect.

jr