CurtPalme.com Home Theater Forum

[skippyar]

What is determining the visual brown tint that I experience whilst watching an older TV [PAL]. (22 years)

Is it component age, a characteristic of the components. The RGB bias or drive shifted.

Here is a simulated example created from a personal photo.

Can this be changed by exchanging components? Is it kelvin temperature chosen when the set was built?


Thanks,

Paul.

[skippyar]

Just having a read through this guide at the moment: https://www.curtpalme.com/forum_archived/viewtopic.php@t=10457.html

[Curt Palme]

Usually (post a screen shot!) it's due to a weak picture tube. Back about 1990, there were a bunch of crap tubes cranked out as manufacturers cheapened everything to keep up with the price war. Zenith back in the 50s to late 70s made awesome tubes for example, as they made their own in the Rauland factory. That changed in the 1980s, and by 1990 the tubes were lasting barely out of the warranty period. I can't remember if they sold Rauland and outsourced the tubes, but they were complete crap for a long time.

[Curt Palme]

Usually (post a screen shot!) it's due to a weak picture tube. Back about 1990, there were a bunch of crap tubes cranked out as manufacturers cheapened everything to keep up with the price war. Zenith back in the 50s to late 70s made awesome tubes for example, as they made their own in the Rauland factory. That changed in the 1980s, and by 1990 the tubes were lasting barely out of the warranty period. I can't remember if they sold Rauland and outsourced the tubes, but they were complete crap for a long time.

[Curt Palme]

to add, there are almost always G2 controls for direct view sets, most also had drive controls, but you'd more or less need to put the tube on a CRT tester to see how far off the three internal electron guns are. If they are too far off, you won't be able to properly balance the white balance, as one gun is usually down in the mud for emission, and the AKB circuit internally (auto white balance circuit) can't compensate for the weak tube.

[Curt Palme]

to add, there are almost always G2 controls for direct view sets, most also had drive controls, but you'd more or less need to put the tube on a CRT tester to see how far off the three internal electron guns are. If they are too far off, you won't be able to properly balance the white balance, as one gun is usually down in the mud for emission, and the AKB circuit internally (auto white balance circuit) can't compensate for the weak tube.

[Tom.W]

A bit OT Curt but how do you like your Sencore CR7000 CRT tester ?

[skippyar]

Thanks for the feedback Curt.

I very gently tweaked the RED and BLUE [bias] on the neckboard last night (eyeballing) which made a big difference, but I can still see that RED is predominate so I would say the DRIVE was the cause.

I am incline to think, where I've pointed to, are the DRIVES as they are next to the mainboard EHT.

Couple of things that I thought odd about this set is there's no FOCUS, no SCREEN, no convergence controls.

Another "characteristic" is when powered ON the image has a sort of 'overdriven' SCREEN effect that calms after a second.

On intense white image (as illustrated) all three colours momentarily flood a little (3D effect) then re-converge.

Hope I'm not being too finicky with this set, I don't really know what's acceptable normal and what needs attention.

I think it's had a rough life with Contrast too high as the top left corner looks burnt.

That CRT tester sounds cool, love to experiment with that type of meter. (Imagine they're pricey.)


Paul.

[skippyar]

[skippyar]