Monitor voluntary dim; possible culprit?

[Hidehiko Ogata]

Hello,

Recently my ~10-year-old multisync monitor (Iiyama MF5017) has
developed intermittent problem, possibly a sign of approaching death.
Being a curious electronics newbie happy to learn more , I'm wondering
if it might be something the limited ability of mine could take care of.
(I can solder/de-solder stuff, and read some rudimentary schematics -
that's about it.)

Specifically, after a powerup, the monitor usually works fine for a
while... until the picture starts to get darker. Very smoothly.
Sometimes it bounces back to normal; othertimes it goes completely
black, in which case a power cycle brings it back (or it has, so far).

Even when the picture has gone completely black, the monitor still
seems "alive": I can hear relay switches respond to different input
frequencies.

I'm quite sure the problem is not on the computers' side, as they work
fine with another monitor. Ditto on screen blankers and such.

Any comments/suggestions would be most welcome. TIA!

 

[RubbishRat]

This was a quality item in it's day and it's not dying by any means. Sounds
like the CRT heaters may be losing their power feed . Taking appropriate
care ( see safety notes http://www.repairfaq.org/ ) Remove the back of the
monitor and check in a dim light if you can see a dull red glow inside the
neck of the CRT during the problem. If not then it could be a bad solder
joint around the CRT neck board. The problem with these monitors is 1/
getting the back off and 2/ removing the tinplate shielding to get to the
works. If the problem isn't caused by a bad solder joint then it might be a
bad cap in the secondary power feed to the heaters. Maybe? hmmmmm .
See how you get on with this.
Best of luck,
Pete

 

[Hidehiko Ogata]

RubbishRat wrote:

8< snippage >8

Thanks for helpful suggestions and a juicy link . Getting the back
off wouldn't be too much hustle; I've done it several times to reach the
frequency-specific pots hidden inside.

I'll try the glow-in-the-dark experiment first. Off to some serious
reading session! =

 

[RubbishRat]

RubbishRat wrote:

8< snippage >8

Thanks for helpful suggestions and a juicy link . Getting the back
off wouldn't be too much hustle; I've done it several times to reach the
frequency-specific pots hidden inside.

I'll try the glow-in-the-dark experiment first. Off to some serious
reading session! =

Sometimes It's difficult to see if the heaters are glowing as the glow is
quite dim but I think there's a good chance that this is the problem as it
fits your symptoms very well. No heaters no picture. If the heaters can be
seen to be OK and still no picture then let us know.
Best of Luck,
Pete

 

[Hidehiko Ogata]

Sometimes It's difficult to see if the heaters are glowing as the glow is
quite dim but I think there's a good chance that this is the problem as it
fits your symptoms very well. No heaters no picture. If the heaters can be
seen to be OK and still no picture then let us know.

Thanks again! To be able to anticipate the potential problem has a
massive impact on confidence, I tell you .

The gremlins seem to have calmed down for the moment (smelling the
poking hands? , so it might be some while before the problem manifests
itself again. I'll let you guys know how it will turn out, definitely!