Hi, Thanks to everyone who has helped me in the past. Now the projection TV I am working on now has the green gun driven very hard, to the point that the unit shuts down after about a minute. I have checked all the transistors, etc and everything points to the M51387P IC. Just wondering if anyone had any ideas before I go and order the chip? (Chassis QV10B)
Thanks

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Shorted tube. Just hope it's an HK short. I can correct that.

Are you in Ohio or anywhere near ? I don't think anyone else can do it.
It entails first wrapping a transformer somewhere to get the floating
filament voltage, then there is a resistor and capacitor you need to
add to the CRT socket board.

Any techs out there listening to this ? Get this, to eliminate changes
when a CRT short intermitts, we have a resistor, about a 4.7K from the
offending cathode to the filament which is now floating. That will
cause a smear in the video of that color. The video output can't drive
all that wire, it acts as an antenna.

It can do it though, I generally find some emitter resistor somewhere
and put a small cap across it to re-equalize the circuit. And folks, if
you ever try this, do not touch the convergence. I mean it.,

I have the drawing of the good modification at work, but my scanner is
at home. I mean I have it drawn out in a schematic. IIRC Mitses video
outs are in a cascode configuration, and that's why the extra
capacitive load bothers them so much. Output impedance is very high.

IIRC it was a .047 and it went in the stage before the output. I will
have to dig that up.

JURB

Donovan wrote:

Hi, Thanks to everyone who has helped me in the past. Now the projection TV I am working on now has the green gun driven very hard, to the point that the unit shuts down after about a minute. I have checked all the transistors, etc and everything points to the M51387P IC. Just wondering if anyone had any ideas before I go and order the chip? (Chassis QV10B)
Thanks

Maybe you could put a heatsink or bigger hs on it. Depends who youre
fixing it for.

NT

Hi, I guess I should have mentioned that I disconnected the drive to the tube and the tube went dark.
While I had the tube disconnected I made some measurments around the the transistors
and IC and it seems to be overdriven right from the IC.

Donovan


"Donovan" wrote:

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Donovan wrote:

Hi, I guess I should have mentioned that I disconnected the drive to the tube and the tube went dark.
While I had the tube disconnected I made some measurments around the the transistors
and IC and it seems to be overdriven right from the IC.

Donovan

you couldnt be a bit more vague could you?

NT