Mystery 21" SGI monitor slowly gets fuzzy

[pentium]

I have not needed to use this massive monitor (so big it has an internal fan) until a few days ago when my Indigo arrived.

At first the screen was fine...


...Then after a while (say ten minuets) The center of the screen (in the middle but spanning to both sides) began to get fuzzy. I really ignored it but then it got ugly.

The screen suddenly began to distort really badly in the center and everything in that distortion was unreadable. I carried on using the top and bottom of the screen but slowly it spread out from the center and eventually the whole screen was fuzzy.
<----I am out of focus but you get the point.

One thing I noticed was that if I raised the contrast fro normal or opened something that had alot of brighter colors in it (like badcaps on firefox), the fuzz would either retreat to the center again or even go away but as soon as you minimized or hid that bright page or window in some way it would come back.


Am I right to suspect dried-out caps or is this more complex?
Forget ditching this one. My SGI's require monitors that use sync-on-green and standard monitors will not cut it.

[kc8adu]

Re: Mystery 21" SGI monitor slowly gets fuzzy

looks like a bad focus divider network(flyback)
iirc that is a mitsubishi.
if a sony a bad crt.
esp if it sometimes snaps and goes normal for a while.
post pics of the inside.

[pentium]

Re: Mystery 21" SGI monitor slowly gets fuzzy

I'll post a pic as soon as I can.
No, there is are no snaps or arcing.
Oh, and if I leave the monitor off for at least half an hour the picture would get better. Leave it alone for a week and the screen completely clears up but then as soon as it's used for ten minuets it starts again.

[pentium]

Re: Mystery 21" SGI monitor slowly gets fuzzy

Here are the pics. BTW, it was made by Hitachi.
http://i11.photobucket.com/albums/a1...itor/front.jpg
http://i11.photobucket.com/albums/a1...nitor/back.jpg
http://i11.photobucket.com/albums/a1...itor/ports.jpg
http://i11.photobucket.com/albums/a1...itor/label.jpg
http://i11.photobucket.com/albums/a1...nitor/info.jpg
http://i11.photobucket.com/albums/a1...tor/inside.jpg
http://i11.photobucket.com/albums/a1...or/flyback.jpg
http://i11.photobucket.com/albums/a1...itor/thing.jpg
http://i11.photobucket.com/albums/a1...or/adjust2.jpg
http://i11.photobucket.com/albums/a1...tor/adjust.jpg

You need to make it easier to just attach pictures. :P

[gonzo0815]

Re: Mystery 21" SGI monitor slowly gets fuzzy

I would opt for some bad solder points and or dried up lytics. But ok, if KC8 is pointing to the flyback , then i would not exlcude this ;-)
this unit must be getting realy hot, that they put in some fans.

[kc8adu]

Re: Mystery 21" SGI monitor slowly gets fuzzy

resolder the flyback pins just in case its the ground for the focus/screen block.
if problem persists its probably a bad fly.

[pentium]

Re: Mystery 21" SGI monitor slowly gets fuzzy

resolder the flyback pins just in case its the ground for the focus/screen block.
if problem persists its probably a bad fly.

Oh great and I can't find my H/V discharge tool.

[starfury1]

Re: Mystery 21" SGI monitor slowly gets fuzzy

Ok me not Monitor guru but have fixed a few

if thats 1988 I read yeah like nearly 20 years of service not bad
All of the above
My first thoughts were EHT horz circuits (possibly psu)

Also check joints on any transistor type packs that are bolted to heat sinks on the pcb,
expansion contraction can and does fracture these solder joints as well.

Higher voltage electrolytic's tend to fail alot too 100 160 Volt type ones

From the photo it looks like one of those large maybe be raised but hard to tell
(for me anyway)

Give it a good visual and check replace caps
rework any joints that are liable to suffer stress or look iffy...solder's cheap.

no guru on them like I said

but this stuff applies to any TV, monitors of that age

Hope for your sake its not a bad flyback

Good luck Pentium and be careful

[kc8adu]

Re: Mystery 21" SGI monitor slowly gets fuzzy

if it is a bad fly try running till its fully hot and adjust focus/g2 for best image.
maybe it will play awhile without drifting.

[pentium]

Re: Mystery 21" SGI monitor slowly gets fuzzy

I'm going to try to check for cold joints first. I still can't find my damn H/V discharge probe.

[gonzo0815]

Re: Mystery 21" SGI monitor slowly gets fuzzy

The only thing, where i am a little coutiouse is the HV cable from the flyback. I usually pull the plug from the crt and discharge it to the black mask or a grounded metall part.
The crt itself can store some hv charge too, buti haven`t had any problems with that.
The HV caps are usually already discharged, so i only short them preemtive with a normal probe or any kind of wire i have handy.
But i ma not a pro too in crt / tv repair.

[pentium]

Re: Mystery 21" SGI monitor slowly gets fuzzy

I usually go with a wood probe with a resistor and an alligator clip on the other end of a length of wire it's attached to and just go over the entire H/V section. I never got the knack of pulling the rubber flyback cup back and inserting the probe.
I also tried removing one with a screwdriver when I was four. In that moment I finally understood how the flyback transformer got it's name.

[gonzo0815]

Re: Mystery 21" SGI monitor slowly gets fuzzy

I also tried removing one with a screwdriver when I was four. In that moment I finally understood how the flyback transformer got it's name.

yes, it is very nasty and a hard learned lesson
But usually under the rubber plug there is a steel clamp.
You can feel it and if proberly compressed you can easily unplug it whitout any problems.
But shure, the rubber may be degrade after time.
I have learned this while trying to put of a car`s engine with defektive ignition lock.
That damn ignition distributor`s rubber plug was realy degraded, and after a realy healthy zapp i refused to try it again
Those MB 190èr cars have had a very robust ignition system