RCA P46720LV Bad Green CRT

Fix the existing crt. Every repair tech I know says its impossible but its not difficult.

NT

There's not much you can "fix" on a CRT without completely rebuilding it, which I suppose is within the realm of a very persistent amature who happens to have a diffusion pump and glassworking equipment but I've not heard of anyone doing that sort of thing at home yet.

If the set is HD capable I'd haul it away for free, might even pay 10 bucks or so for it, but if it's only a SD projector forget it, he should be paying you to dispose of it. There's some cool optics in a CRT projection set though if you're into experimenting with that sort of thing.

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Please, elaborate on this if you would...

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James, thanks for the opinion... That's what I needed. He indicated the repair shop offered him $50 for it.

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The "bulb" he was referring to would be the "green gun" All color CRT's have 3 guns, red, green, and blue. If the"bulb" is shorted, i.e. the cathode shorted to the heating element or possibly to the screen grid, it's possible to remove the short.You would have to have access to what is referred to as a CRT Tester/Rejuvenator. Sencore and B&K are still around. If the cathode or grids are open there's no hope. Either rebuild the tube or replace it. They are available for a lot less than $250. You'll never recover you costs for this, but if you like tinkering, enjoy. Have a good day! Mike

Do those work on projectors like the P46720LV ?

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Thanks for the information. Where would I obtain a replacement green CRT. This is a projection set that uses three separate CRTs...

Kirk S.

Sure. I've done this many a time, so wont take much notice of the naysayers that always come along.

The trick is very simple, boost heater voltage. Not by a measly 10%, thats semi-pointless, 33% V boost for mild cases, 66% for the worse ones. The simplest way to boost is to add an extra turn round the LOPTR core, just thread some pvc wire through it and hook up in series with the heater feed. If V drops, connect the turn the other way round to get boost.

I once did an experiment, took a set with nothing visible on screen at all, solely due to dire emission, and hit it with IIRC +70& Vboost and

+10% EHT boost. All guns came up, brightness was fine, but tracking of the 3 channels was a mess.

Dont boost EHT unless you understand the issues involved, dont do it at home and dont do it on repair sets.

Ah, there is one gotcha with this boost method: the tube must never have been touched by those dreaded cathode zapping rejuvenators. If you see a tube that smears, boosting it is a waste of time IME.

NT

Not recommended. Gamma changes significantly over time, and a new tube working with old tubes makes for bad colour tracking. If you do replace a tube, putting an old one in from a scrapper would give a better picture.

NT

CRT.

Hence my dilemna... No spare parts...

Thanks...

Kirk S.