Re: Mitsubishi VS-466R Dark Picture


<meow2222@xxxxxxxxx> wrote in message
news:1164551814.599815.21790@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Leonard Caillouet wrote:

Experimented with both increasing filament voltage and restoration. If
you
understand what each does and why they work or do not, you would find
that
if there is sufficient emitter material left in the cathode, either can
work, but fiddling with flyback winding is a riskier approach. With the
better restoration equipment we have had good results on many sets.

If you believe that either method always works, you are making a hell of
an
assumption. If a tube is too far gone or if the phosphors are worn out,
you
wont get good results no matter what you do.

Leonard

The 2 methods work in different ways, though both improve emission.
Rejuv strips off surface contaminants from the emitter, voltage
boosting simply ups the thermal emission of electrons - and this is a
process that will work with any emitter material afaik, just a basic
physics property. So its hard for it to fail, though not impossible. It
isnt going to correct any other tube faults, or deal with shorts, as a
rejuve machine can, but it will increase cathode emission. One way it
can go wrong is overheating the deflection assembly, but this is rare
in practice.

I once did a test case with this method, found a set with emission so
bad nothing could be seen on screen, and it was an old sony, famous for
not responding to rejuvenation. I pushed it hard, +70% heater voltage
boost and IIRC +10% EHT boost. The heaters glowed yellow instead of
red-orange. The result was ok performance, and I kept it, since it
wasnt fit to pass on like that, and it ran fine for years, no visible
deterioration.

When run at rated heater V, not all the cathode area emits. Some is too
cool to work. Boosting heater power has 2 effects: it ups the emission
of the damaged or worn out areas, and it brings into action more
cathode area, the outlying bits that didnt emit before.

I certainly havent been doing it 30 years, but in the time I did I saw
inconsistent results with rejuve, which would usually fade again in a
few months, and cause heavy smearing when emission faded again. Heater
boosting otoh is a relatively sure bet. I'm talking here of 33% & 50% V
boosts, not the old fashioned 10% boost, which is of little use.


NT

Every set that I have tried 10% to 50% filament boosting on deteriorated
within months to the point that it was unacceptable. We have mixed results
with restoration but many of them stick. The degree to which one calls
success may vary with expectations as well. If I can't get good gray scale
tracking I do not consider the process successful. Could be that we have
only tried boosting CRTs that would not have been acceptable anyway.

Leonard

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Relevant Pages

  • Re: Mitsubishi VS-466R Dark Picture
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    ... and they claim the sound becomes especially good ... But then emission is lower so gm would be lower, ... (other than perhaps longer heater life?) ... they probably have volume controls that go to 11. ...
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