CurtPalme.com Home Theater Forum

[Don Mummey]

Recently, the red CRT has a very bright raster pattern only, picture is only visible on green & blue CRTs.

Only the green and blue CRT's will respond to picture-mute and individually on and off using RC-6321 remote ... red will respond only with a minor decrease in intensity and an occasional blink-off but immediately turn on again.

During power-on, the red is the first to turn on, ramping up to full intensity unlike the other two which blink on when enabled by their control circuits a few seconds later.

What should be my next diag step?

[Curt Palme]

Swap the neck cards on the backs of hte tubes. All three are identical. If the red stays on, it is probably shorted, but hopefully it's just the neck card. I can repair that or replace it for you.

If it's the tube, I've got those as well.

[Curt Palme]

Swap the neck cards on the backs of hte tubes. All three are identical. If the red stays on, it is probably shorted, but hopefully it's just the neck card. I can repair that or replace it for you.

If it's the tube, I've got those as well.

[Don Mummey]

I swapped the red and blue neck cards. As you mentioned in your NEC Layout and Setup doc, there's a small fan on the
green card.

The red neck card must certainly be bad as the blue now has raster only and there is a picture on the red CRT.

However, the symptom that did not change is that Red is still the first to lite up seemingly coincidental with it's filament
warmup, ramping up to what seems to be an exceptionally bright non-raster-only and then the picture displays when the
green and blue turn on. Yes, the blue now displays a raster only (by swapping the neck cards) but it still turns on
simultaneously with green during power-up. When red begins to lite up, it entirely covers the face of the CRT (sides
and top/bottom are bowed inwards) but it extends all the way into the corners of the CRT. When green and blue
turn on a few seconds later, the red snaps down to it's 'normal' phosphor size and is REALLY bright.

The blue (with the bad neck card) still responds to pic-mute and blue CRT on/off with the remote control, just as green does. While red will stop displaying it's picture in pic-mute or off, the face of the CRT is still glows brightly unlike the other two which really go dark (or relatively so).

When individually turning off blue or green, the red actually gets brighter - like twice as much - and returns to it's
previous state when whichever CRT is turned back on.

More than just a neck card, wouldn't you agree? I'm anxious to swap the neck cards back to their original positions
before it smokes the blue card as well. I probably don't have 60 seconds of run time on it to make these observations
but I'll wait til you concur.

What should I try next?

[Curt Palme]

I think the only problem is the neck board. The NECs have massive AKB circuits (auto brightness) that rely on proper tube light and video output to balance the gains of all three tubes. WIth one tube not working, the AKB goes all over the place.

So I'm pretty sure a new neck board will do it.

Send that neck board to me for testing and repair, shoot me an email to curtpalme@shaw.ca and I'l let you know how to send it in.

Cheers!

[Curt Palme]

I think the only problem is the neck board. The NECs have massive AKB circuits (auto brightness) that rely on proper tube light and video output to balance the gains of all three tubes. WIth one tube not working, the AKB goes all over the place.

So I'm pretty sure a new neck board will do it.

Send that neck board to me for testing and repair, shoot me an email to curtpalme@shaw.ca and I'l let you know how to send it in.

Cheers!

[Mark_A_W]

I agree.

Dead neckboard.


Maybe has some white balance issues, but AKB should compensate, and it's a bit hard to tell until everything is functioning properly.