Monitor shuts down after a while...

[Luca T.]

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Hello,
i've a Nokia CRT monitor (447XS) for some years now and lately (a week
or so) i am experiencing a problem with it.
The monitor powers up correctly and works for some minutes, after that
the image on the screen becomes black (there is no noise when doing so
nor i can hear any noise while using it).
Usually this is fixed by "beating" it a few times.
This seems to repeat for some times (the image goes black, i beat it,
the image comes back, after some seconds it goes black again and so on)
until the image works properly. When this happens it usually works fine
for hours unless the monitor "goes to sleep" then, by moving the mouse
(to wake it up) the monitor does nothing until i beat it again.

I checked all the cables and they are perfectly connected.

Any idea about what might cause this strange behaviour?

I would say that some solderings aren't ok... but then why does it work
fine for hours after being beaten a few times? The problem seems to
happen only when the monitor is "cold" or used for little time.

Thank you in advance,
~ Luca
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[mike]

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Hello,
i've a Nokia CRT monitor (447XS) for some years now and lately (a week
or so) i am experiencing a problem with it.
The monitor powers up correctly and works for some minutes, after that
the image on the screen becomes black (there is no noise when doing so
nor i can hear any noise while using it).
Usually this is fixed by "beating" it a few times.
This seems to repeat for some times (the image goes black, i beat it,
the image comes back, after some seconds it goes black again and so on)
until the image works properly. When this happens it usually works fine
for hours unless the monitor "goes to sleep" then, by moving the mouse
(to wake it up) the monitor does nothing until i beat it again.

I checked all the cables and they are perfectly connected.

Any idea about what might cause this strange behaviour?

I would say that some solderings aren't ok... but then why does it work
fine for hours after being beaten a few times? The problem seems to
happen only when the monitor is "cold" or used for little time.

Thank you in advance,
~ Luca
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The weak link is the solder connection from the crt board to the crt
socket. But in every case I've found only one color goes.

Another weak link is the connection to the big resistor, or two, or
three in the power supply.

I've seen more than a few intermittent problems solved by blowing the
dust out of the monitor...but your problem seems to be when cold, not hot.
mike

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[Luca T.]

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mike wrote:

Thank you for the fast answers.

| The weak link is the solder connection from the crt board to the crt
| socket. But in every case I've found only one color goes.

You mean the CRT socket connected to the cathode tube, right?

| Another weak link is the connection to the big resistor, or two, or
| three in the power supply.

I'll check for "big resistors" in the power supply area. Btw, for "big
resistor" do you mean big as in phisical size or value?

| I've seen more than a few intermittent problems solved by blowing the
| dust out of the monitor...but your problem seems to be when cold, not hot.
| mike

I'll try blowing the dust out of the monitor as you suggest as first
thing tomorrow.

Thank you again,
~ Luca

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[3T39]

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Hello,
i've a Nokia CRT monitor (447XS) for some years now and lately (a week
or so) i am experiencing a problem with it.
The monitor powers up correctly and works for some minutes, after that
the image on the screen becomes black (there is no noise when doing so
nor i can hear any noise while using it).
Usually this is fixed by "beating" it a few times.
This seems to repeat for some times (the image goes black, i beat it,
the image comes back, after some seconds it goes black again and so on)
until the image works properly. When this happens it usually works fine
for hours unless the monitor "goes to sleep" then, by moving the mouse
(to wake it up) the monitor does nothing until i beat it again.

I checked all the cables and they are perfectly connected.

Any idea about what might cause this strange behaviour?

I would say that some solderings aren't ok... but then why does it work
fine for hours after being beaten a few times? The problem seems to
happen only when the monitor is "cold" or used for little time.

Thank you in advance,
~ Luca

First on my list of suspects is bad solder jounts at the CRT heater pins on
the CRT neck since it affects all colours at once. To fix this you have to
remove the metal guard covering the printed circuit board and resolder the
pins. or maybe the Power supply to the heaters has a loose conection. but
because of the nature of the fault I think a bad solder connection somewhere
is almost certain.
Pete