Mitsubishi VS-4504CA - Hard green drive.

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

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)

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

NT

On Wed, 11 Oct 2006 05:20:37 -0700, meow2222 Has Frothed:

I actually epoxy'd an additional HS onto my Pana 51 STK HS. After I finally got around to fixing it, I felt the HS and it was pretty hot. Figured it wouldn't hurt to add some square inches to the original seeing there was plenty of space inside the box.

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

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and the tube went dark.

transistors

you couldnt be a bit more vague could you?

NT