My 4+ year old ViewSonic E790 isn't quite as sharp as it used to be.
What causes this and what can I do to fix it?

--adam

"CJT" wrote in message
...

There are several possibilities, including (in no particular order) -

SNIP
aging of the CRT
SNIP

How can aging of the CRT result in picture blurring ?

I know that kathodes or heaters could wore out or that phosphor could decay,
but what effect would cause blurriness ?

Most of the units I have seen got that way aither due to HV pots (for focus
and screen) and due to demagnetisation of the calibration magnets and rings.
IOW, nothing that couldn't be trimmed and retweaked...

Branko

Adam:
Most likely age and normal wear and tear....
the CRT ain't what she used to be.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -



"Adam" wrote in message
k.net...
My 4+ year old ViewSonic E790 isn't quite as sharp as it used to be.
What causes this and what can I do to fix it?

--adam

Adam wrote:
My 4+ year old ViewSonic E790 isn't quite as sharp as it used to be.
What causes this and what can I do to fix it?

--adam

There are several possibilities, including (in no particular order) -

drift in the focus circuit
drift in the video circuits
cable damage
a problem with the degaussing circuit
aging of the CRT
changes in your eyesight g

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SIOL wrote:
"CJT" wrote in message
...


There are several possibilities, including (in no particular order) -


SNIP

aging of the CRT

SNIP

How can aging of the CRT result in picture blurring ?

what I had in mind is mechanical changes caused by thermal cycling
that result in misalignment

maybe that's a longshot

I know that kathodes or heaters could wore out or that phosphor could decay,
but what effect would cause blurriness ?

Most of the units I have seen got that way aither due to HV pots (for focus
and screen) and due to demagnetisation of the calibration magnets and rings.
IOW, nothing that couldn't be trimmed and retweaked...

Branko




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minimize spam. Our true address is of the form .

On Wed, 15 Dec 2004 06:20:22 GMT, Adam put finger
to keyboard and composed:

My 4+ year old ViewSonic E790 isn't quite as sharp as it used to be.
What causes this and what can I do to fix it?

Adjust the focus control on the flyback transformer. However, be
warned, there are *very* high voltages in that area.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

Picture tubes ware out like anything does . Many tv sets have a resistor
in series with the tube filament ... i dont know if they do this in
monitors ? that resistor can be bypassed with a wire to boost the
filament and sharpen up the tube once again .
Make sure to try and wash the screen off ( do you smoke ? and adjust the
focus first .

Best fix is to buy a flat panel lcd monitor

"SIOL" bravely wrote to "All" (15 Dec 04 07:31:51)
--- on the heady topic of " What cause CRT blur?"

SI From: "SIOL"

SI "CJT" wrote in message
SI ...

There are several possibilities, including (in no particular order) -

SNIP
aging of the CRT
SNIP

SI How can aging of the CRT result in picture blurring ?

SI I know that kathodes or heaters could wore out or that phosphor could
SI decay, but what effect would cause blurriness ?


The effective interelectrode potentials in the electron gun are
dependant on the beam current. If a gun is too weak the beam doesn't
focus at the right distance anymore.


SI Most of the units I have seen got that way aither due to HV pots (for
SI focus and screen) and due to demagnetisation of the calibration magnets
SI and rings. IOW, nothing that couldn't be trimmed and retweaked...

Modern crt's did away with the colour convergence coils so this can't
be adjusted anymore. It's the price to pay for needing less circuitry.

A*s*i*m*o*v

.... I worked hard to attach the electrodes to it.

CJT:
Come on now..... we have all seen this.
As the CRT ages and the picture gets dimmer and with less contrast.....
the user continues to jack up the brightness and contrast to
compensate and eventually the controls "run out of gas" and the result
is a soft, pale picture that maybe is blooming and looks soft.
electricitym
= = = = = = = = = = = =

wrote:
CJT:
Come on now..... we have all seen this.
As the CRT ages and the picture gets dimmer and with less contrast.....
the user continues to jack up the brightness and contrast to
compensate and eventually the controls "run out of gas" and the result
is a soft, pale picture that maybe is blooming and looks soft.
electricitym
= = = = = = = = = = = =

another good explanation

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The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

Attn: electricitym:
It was not CJT that questioned how a old CRT could start looking soft.... it
was Branko / SIOL.
Your explanation was right on however.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


wrote in message
oups.com...
CJT:
Come on now..... we have all seen this.
As the CRT ages and the picture gets dimmer and with less contrast.....
the user continues to jack up the brightness and contrast to
compensate and eventually the controls "run out of gas" and the result
is a soft, pale picture that maybe is blooming and looks soft.
electricitym
= = = = = = = = = = = =

"Asimov" wrote in message


Modern crt's did away with the colour convergence coils so this can't
be adjusted anymore. It's the price to pay for needing less circuitry.

Not quite. They did get rid of some permanent magnets, but they have
replaced them with coils that are dynamically controlled can be tweaked
through service connector. That is, if you happen to have certain software
and interface.

Still, even on those units one can glue a few magnets on and correct some
minor things even without the software controll.

Branko

"sofie" wrote in
:

Attn: electricitym:
It was not CJT that questioned how a old CRT could start looking
soft.... it was Branko / SIOL.
Your explanation was right on however.

One more reason is that the aging,harder-driven cathode emits from a much
larger area,and the wider beam eventually hits the edges of the electron
gun apertures.That's what happened with TEK 528 waveform monitor
CRTs,according to the TEK CRT group.

--
Jim Yanik
jyanik-at-kua.net