Fixing shadow effect on monitor

P

Pepebuho

Guest
Hi
I have a Panasonic P70 monitor. It is a good one.
After a repair (the green cannon went south) the monitor
shows some shadow effect on the horizontal plane.

I sent it to two technicians, the original one and a very trusted
one. The original one just told me the tube was old and that was the
reason.
The trusted one checed everything out and he told me the
monitor was within spec.

My question is . How can I solve that shadow effect?
I imagine I could live with it, but I don't want to if I can avoid it.
And I do not want to deep six the monitor becaus it is a good one,
giving me 17" screen, 1280 x 1024 @ 85Hz, the image used to be quite
good.

I appreciate any input.

Thanks!

Javier
 
"Pepebuho" <p1e2p3e4b5u6h7o8@pananet.com> wrote in message
news:bq6iu5025bv@enews1.newsguy.com...
Hi
I have a Panasonic P70 monitor. It is a good one.
After a repair (the green cannon went south) the monitor
shows some shadow effect on the horizontal plane.

I sent it to two technicians, the original one and a very trusted
one. The original one just told me the tube was old and that was the
reason.
The trusted one checed everything out and he told me the
monitor was within spec.

My question is . How can I solve that shadow effect?
I imagine I could live with it, but I don't want to if I can avoid it.
And I do not want to deep six the monitor becaus it is a good one,
giving me 17" screen, 1280 x 1024 @ 85Hz, the image used to be quite
good.

I appreciate any input.

Thanks!

Javier
Click to expand...
Sounds like the tube is likely shot, unless the green drive is just turned
up too high. When a tube ages it tends to get soft, and the drive waveform
clips in order to get sufficient brightness hence the ghosting. If the tech
told you the tube is bad it probably is, but he likely has a CRT analyzer
and could check it for you fairly easily.
 
The tech that said the monitor was in specs, probably checked it
electrically, and paid no attention to the tube. I have seen this before,
where they check out the performance of the monitor right to the tube socket
with a scope, and test generator. But, the tech doesn't carefully look at
the tube for such details.

Considering the age of the monitor and your description, I would think that
the tube is bad. I would believe the tech that indicated this.

As for tube monitors, they are going very cheap these days, in comparison to
a few years ago. The main stream of them at the low prices will soon no
longer be available. This is until they run out of CRT's. All the major
manufactures are no longer producing CRT's for general monitors. They will
only be making the LCD types for computers. The only CRT monitors that will
be available will be the very high end ones, that will be very expensive.
If you like CRT monitors, grab some while you can!

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"Pepebuho" <p1e2p3e4b5u6h7o8@pananet.com> wrote in message
news:bq6iu5025bv@enews1.newsguy.com...
Hi
I have a Panasonic P70 monitor. It is a good one.
After a repair (the green cannon went south) the monitor
shows some shadow effect on the horizontal plane.

I sent it to two technicians, the original one and a very trusted
one. The original one just told me the tube was old and that was the
reason.
The trusted one checed everything out and he told me the
monitor was within spec.

My question is . How can I solve that shadow effect?
I imagine I could live with it, but I don't want to if I can avoid it.
And I do not want to deep six the monitor becaus it is a good one,
giving me 17" screen, 1280 x 1024 @ 85Hz, the image used to be quite
good.

I appreciate any input.

Thanks!

Javier
 
On Thu, 27 Nov 2003 23:30:30 -0500, "Pepebuho"
<p1e2p3e4b5u6h7o8@pananet.com> wrote:

[ Panasonic P70 monitor. ]

Never yet saw a bad CRT. Am still using old TVs, too, from the
early seventies, all of them with still good CRTs. Imho, to consider
a bad CRT is only a useful assumption after all other possibilities
really have been checked with definitely certain results.

Try to get a good monitor test software from the net (like the
one rom Nokia), and check out the picture. Perhaps you have
some riniging in the video amplifier.
H.
 
Well I worked for 5 years for a major Monitor/Television repair company who
will remain nameless, but they spell their name with only one L so you
should know who that is, and I have replaced uncountable bad picture tubes,
some of them right off the assembly line fresh from the manufacturer. Shadow
masks break free, grids break and short out and the red phosphor on the
screen and coatings on the cathodes wear out. New CRT's are so cheap that
the coating on the cathodes wear out in 5 years or so. I guess that's how
Circut City is selling a 32" inch TV for 200 dollars US today (day after
thanksgiving), when I was in the A/V repair business that tube alone cost
over $500, and I have many monitors around here that have "weak" tubes (
mostly poor red response) one of these even has a geunine Trinitron tube. So
when Sharp and LG get around 80% yeild on larger LCD panels, the CRT will be
effectively dead. Just my 2 cents worth.
Ron

P.S. yes I do own a CRT analyzer, so I'm not just looking at the picture and
proclaiming a "Bad" CRT, I can prove the lack of gain on any color or the
presence of shorts.


"Heinz Schmitz" <HeinzSchmitz@gmx.net> wrote in message
news:hpkesv0uoltnam4gug2kr8ad3f68rqof2k@4ax.com...
On Thu, 27 Nov 2003 23:30:30 -0500, "Pepebuho"
p1e2p3e4b5u6h7o8@pananet.com> wrote:

[ Panasonic P70 monitor. ]

Never yet saw a bad CRT. Am still using old TVs, too, from the
early seventies, all of them with still good CRTs. Imho, to consider
a bad CRT is only a useful assumption after all other possibilities
really have been checked with definitely certain results.

Try to get a good monitor test software from the net (like the
one rom Nokia), and check out the picture. Perhaps you have
some riniging in the video amplifier.
H.
Click to expand...
 
"Heinz Schmitz" bravely wrote to "All" (28 Nov 03 14:52:53)
--- on the heady topic of "Re: Fixing shadow effect on monitor"

HS> From: Heinz Schmitz <HeinzSchmitz@gmx.net>
HS> Subject: Re: Fixing shadow effect on monitor
HS> Organization: T-Online
HS> Xref: aeinews sci.electronics.repair:12787

HS> On Thu, 27 Nov 2003 23:30:30 -0500, "Pepebuho"
HS> <p1e2p3e4b5u6h7o8@pananet.com> wrote:

HS> [ Panasonic P70 monitor. ]

HS> Never yet saw a bad CRT. Am still using old TVs, too, from the
HS> early seventies, all of them with still good CRTs. Imho, to consider
HS> a bad CRT is only a useful assumption after all other possibilities
HS> really have been checked with definitely certain results.

HS> Try to get a good monitor test software from the net (like the
HS> one rom Nokia), and check out the picture. Perhaps you have
HS> some riniging in the video amplifier.
HS> H.

You must be living a very sheltered life, I've seen plenty of bad crt's.
Those blue label Samsung for example going weak. The heater to cathode
shorts of so many others. BTW I still have tv's from the 60's and I've
seen plenty of even those with bad crt's. I don't know where you come
off saying that...

Presently I have this pet tough dog with a crt problem but I don't know
what is wrong with it. The crt is like new, bright, plenty of emission
but it just won't balance yellow properly. I set the pure colours with a
light meter to the same levels as another identical monitor and I get a
nice white temperature but the yellow always turns out looking pale and
insipid. However, the red bias has to be turned down low and drive high.
Can't figure it out but I'll bet it's the crt red gun is too hot!

.... I know flyback, ultor, and 47 other dangerous words.
 
"Heinz Schmitz" <HeinzSchmitz@gmx.net> wrote in message
news:hpkesv0uoltnam4gug2kr8ad3f68rqof2k@4ax.com...
On Thu, 27 Nov 2003 23:30:30 -0500, "Pepebuho"
p1e2p3e4b5u6h7o8@pananet.com> wrote:

[ Panasonic P70 monitor. ]

Never yet saw a bad CRT. Am still using old TVs, too, from the
early seventies, all of them with still good CRTs. Imho, to consider
a bad CRT is only a useful assumption after all other possibilities
really have been checked with definitely certain results.

Try to get a good monitor test software from the net (like the
one rom Nokia), and check out the picture. Perhaps you have
some riniging in the video amplifier.
H.
Click to expand...
You must not have worked on many recent monitors and TV's, I've lost count
of the number of verified bad CRT's I've dealt with, weak emission, shorted
guns, shifted shadow mask, gassy, granted when people say they think the
tube is shot it's almost always not, but when people think it just needs an
adjustment it's often the tube.
 
If it is doing what I call flaring it might be the tube, but that's good !
Monitors are so difficult to repair sometimes that changing a tube is not
considered hard, and a used one should be obtainable. If you're lucky enough to
get the exact same model you can just leave the yoke in place on the neck and
it becomes pretty much a meatball job.

Lacking a cheap used tube for it I would consider boosting the filament voltage
or even a good tune up. Getting the biases way down and increasing the G2 goes
a long way sometimes.

JURB
 
On Friday, 28 Nov 2003 14:16:04 -500, "Asimov"
<Asimov@-removethis-bbs.juxtaposition.dynip.com> wrote:

You must be living a very sheltered life, I've seen plenty of bad crt's.
Click to expand...
Then you must have seen many more CRTs than I have, with most of them
having still good tubes :).
I wanted to point out, that statistically the chance of having a
"worn out" (that is, a CRT which did work properly before) tube, is
imho small in comparison to other faults to be expected in TVs or
monitors.

Those blue label Samsung for example going weak. The heater to cathode
shorts of so many others. BTW I still have tv's from the 60's and I've
seen plenty of even those with bad crt's. I don't know where you come
off saying that...
Click to expand...
I'm arguing from a position which is: If I get a faulty monitor or TV,
I think of everything else, before I start thinking of a bad picture
tube.

Presently I have this pet tough dog with a crt problem but I don't know
what is wrong with it. The crt is like new, bright, plenty of emission
but it just won't balance yellow properly. I set the pure colours with a
light meter to the same levels as another identical monitor and I get a
nice white temperature but the yellow always turns out looking pale and
insipid. However, the red bias has to be turned down low and drive high.
Can't figure it out but I'll bet it's the crt red gun is too hot!
Click to expand...
Aren't you doing a static adjustment and then watching results
depending on a function? What happens, if you exchange the socket
boards with the video amp circuitry?
H.
 
I'm arguing from a position which is: If I get a faulty monitor or TV,
I think of everything else, before I start thinking of a bad picture
tube.
Click to expand...

That I will definitly agree with, whenever a TV fails everyone always
assumes it's the tube, it almost never is, but tubes do fail. The thing is
when they do, people assume it just needs an adjustment, tubes usually wear
over time rather than fail outright.
 
Common problem with P70 and PL70 is electrolytics C1066,C1166 and C1266
failing (1uf/100V) . Also C516 is 1uF/100V which fails often too.
When those three fail the picture gets dim and somebody might have
raised the G2 to compensate it. That could cause shadowing,
would have to see it to be sure.

oh3lku
 
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