I know this is an old TV, but I have had it so long I hate to get rid
of it, at any rate I have noticed that the screen?picture has gotten
dark and if the room I use it in is to bright I can not see areas of
movies that are in the shadows? Any ideas? Or should I just get a new
one?

Mike

wrote:

I know this is an old TV, but I have had it so long I hate to get rid
of it, at any rate I have noticed that the screen?picture has gotten
dark and if the room I use it in is to bright I can not see areas of
movies that are in the shadows? Any ideas? Or should I just get a new
one?

Mike

I take it the whole picture is dimmer now. If so it most likely is
falling crt emission. Reduced emission is easily fixed by wrapping a
turn of wire round the loptf and putting this in series with the crt
heater. You'll often find connect it one way round it works like new,
connect it the wrong way and it'll be much dimmer.

Its diyable if you're properly aware of the dangers in tvs. The work
itself is fairly elementary.

If someone suggests a crt rejuvenator or booster, dont. Those things
give a short term boost but really kill the tube's long term prospects
by causing heavy smearing. Upping the heater voltage is generally a
long term fix (perhaps counterintuitively).


NT

ha escrito:

I know this is an old TV, but I have had it so long I hate to get rid
of it, at any rate I have noticed that the screen?picture has gotten
dark and if the room I use it in is to bright I can not see areas of
movies that are in the shadows? Any ideas? Or should I just get a new
one?

Mike

you could adjust the SCREEN control on the line transformer a bit,
using an insluted flat bladed screwdriver. you'll know its too high if
white horizontal lines appear in the picture. worth a try.

-B.

b wrote:
ha escrito:

I know this is an old TV, but I have had it so long I hate to get rid
of it, at any rate I have noticed that the screen?picture has gotten
dark and if the room I use it in is to bright I can not see areas of
movies that are in the shadows? Any ideas? Or should I just get a new
one?

Mike

you could adjust the SCREEN control on the line transformer a bit,
using an insluted flat bladed screwdriver. you'll know its too high if
white horizontal lines appear in the picture. worth a try.

-B.

it could in principle be either of these 2 faults, poor emission or
screen adjustment. OPs never give enough detail, and I've given up
asking for info as it never comes back.


NT

wrote in message
ups.com...

it could in principle be either of these 2 faults, poor emission or
screen adjustment. OPs never give enough detail, and I've given up
asking for info as it never comes back.

We had a salesman who did that all the time. I had a stamp made up which
said, "Insufficient Information" which we stamped on his RFQs.

I have been restoring and rejuving CRTs for nearly 30 years and have had
many successes with the process. It depends on the tube. In this case,
however, it is not likely worth the trouble. This set's CRTs often did not
respond well to restoration. Some do, some do not. Increasing the filament
voltage is actually a short term solution itself and may have little benefit
if the phosphors are worn out. In general, this set is beyond its useful
life, but the only way to know for sure is to examine the condition of the
phosphors and test the emission. Restoration might be worth a shot but most
techs would not bother on a set this age.

Boosting the filament voltage with flyback windings is not something that I
would consider safe for most DIYers. It is rarely the best option unless
there is a HK short.

Leonard

wrote in message
oups.com...
wrote:
I take it the whole picture is dimmer now. If so it most likely is
falling crt emission. Reduced emission is easily fixed by wrapping a
turn of wire round the loptf and putting this in series with the crt
heater. You'll often find connect it one way round it works like new,
connect it the wrong way and it'll be much dimmer.

Its diyable if you're properly aware of the dangers in tvs. The work
itself is fairly elementary.

If someone suggests a crt rejuvenator or booster, dont. Those things
give a short term boost but really kill the tube's long term prospects
by causing heavy smearing. Upping the heater voltage is generally a
long term fix (perhaps counterintuitively).


NT


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That would be hard to do since on this set, and most RPTV sets you will not
find a screen control on the LOT.

Leonard

"b" wrote in message
oups.com...

ha escrito:

I know this is an old TV, but I have had it so long I hate to get rid
of it, at any rate I have noticed that the screen?picture has gotten
dark and if the room I use it in is to bright I can not see areas of
movies that are in the shadows? Any ideas? Or should I just get a new
one?

Mike

you could adjust the SCREEN control on the line transformer a bit,
using an insluted flat bladed screwdriver. you'll know its too high if
white horizontal lines appear in the picture. worth a try.

-B.


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Leonard Caillouet wrote:

I have been restoring and rejuving CRTs for nearly 30 years and have had
many successes with the process. It depends on the tube. In this case,
however, it is not likely worth the trouble. This set's CRTs often did not
respond well to restoration. Some do, some do not. Increasing the filament
voltage is actually a short term solution itself

Short lived results from heater boosting wasnt my experience, though it
was my initial expectation. In fact those repairs lasted very much
better than rejuves, and worked more or less 100% of the time, unlike
rejuvenation. I swore off rejuves very early, and used heater boosting.
At that time I never came across anyone else using the same approach,
they were all doing rejuve, and paying silly money for base connectors
for them. And they were all were unable to revive various types of
tube, esp Sonys, so I picked up all the old Sonys.


Boosting the filament voltage with flyback windings is not something that I
would consider safe for most DIYers. It is rarely the best option unless
there is a HK short.

Rarely the bst option? It always worked IME. I'm going to take a guess
you've stuck with rejuv and done little or no heater boosting. I'm the
other way round.


NT

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

wrote in message
ps.com...
Leonard Caillouet wrote:

I have been restoring and rejuving CRTs for nearly 30 years and have had
many successes with the process. It depends on the tube. In this case,
however, it is not likely worth the trouble. This set's CRTs often did
not
respond well to restoration. Some do, some do not. Increasing the
filament
voltage is actually a short term solution itself

Short lived results from heater boosting wasnt my experience, though it
was my initial expectation. In fact those repairs lasted very much
better than rejuves, and worked more or less 100% of the time, unlike
rejuvenation. I swore off rejuves very early, and used heater boosting.
At that time I never came across anyone else using the same approach,
they were all doing rejuve, and paying silly money for base connectors
for them. And they were all were unable to revive various types of
tube, esp Sonys, so I picked up all the old Sonys.


Boosting the filament voltage with flyback windings is not something that
I
would consider safe for most DIYers. It is rarely the best option unless
there is a HK short.

Rarely the bst option? It always worked IME. I'm going to take a guess
you've stuck with rejuv and done little or no heater boosting. I'm the
other way round.


NT


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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

wrote in message
ups.com...
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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Leonard Caillouet wrote:

Every set that I have tried 10% to 50% filament boosting on deteriorated
within months to the point that it was unacceptable.

I'm quite surprised to hear that, and am wondering why the difference.
I dont know.

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.

Yes. I had no problems there, except for the experimental boost set,
where the resulting gun matching was way out - but no-one would ever
attempt to boost something that bad for commercial reasons.

Could be that we have
only tried boosting CRTs that would not have been acceptable anyway.

Leonard

How have you chosen your boost voltages? Have you just given it enough
to look ok, since you mention using as low as 10%, or have you waded
right in with 33% for mild cases and 50% for the baduns? The latter is
what I did, gives it enough margin to look good for many years to come.

The one type of tube I didnt have good results boosting was ones that
had been rejuved. Once that has been done, really its a death sentence.
With those, a boost can get you a short term result, but the
reappearance of smearing soon ruined things.

when I first learnt of heater boosting I got very much the impression
it shouldnt be overdone, but my own experience was pretty much the
opposite, that tubes can be hit very hard and consistently survive, and
that its underboosting thats unsatisfactory, not over. 50% V boost is a
good double the heater power, far outside design margins, yet rarely
any problem with it.


NT