monitor with dark stain

[rotesil]

I recently bought a new monitor 20", but when it lights, a dark stain appears, when I load a game, disappears. the colors are correct, CRT owns demag coil , and speakers are armoured, it is not
magnetization stain, it is totally dark... any idea?

 

[backflipper]

That picture is tiny. Is it my browser(Chrome)?

Welcome to the forum...

Is the black stain present when the unit is off or does it appear when the unit is on?

Can you let us know more details such as what the game is, monitor model #...?

 

[rotesil]

it is when the monitor is on, only the monitor, without game. monitor is
a Wei-ya 820H 20in vertical deflection is measuring 13.4... with game
running, the stain disappears... (sorry, my english is bad...)

 

[P-Man]

if it doesn't affect the actual game image, then where is the problem? or do you like staring at blank pictures?

 

[joe34]

below: saw this reply on another forum... fyi:

____________________________________________________

Hey!

I've seen this one!

I'm an arcade tech that has been working on CRT monitors for about twenty years now.

Your problem is a small capacitor. Usually 3.3 or 4.7 uf 50v.

Capacitors can fail, (do fail) fresh from the manufacturer.

Randy Fromm's monitor flowcharts say "Is the picture distorted or curved" --> "Electrolytic Capacitor failure, this is the most common failure of all. It is best to replace all the Electrolytic Capacitors at this time"

He is right. Replacing all the Electrolytic Capacitors will solve this problem.

Interestingly, the black 'blob' with edges that fade away from the 'spot' will look the same without a signal applied. Turn up the 'screen' knob on the flyback until the entire screen looks grey with retrace lines and the 'blob' will be dark black.

It's a capacitor.

 

[karlcdoe]

hmmm, so have you actually fixed it then? good work if so, otherwise it'll be interesting to see what happens. Isn't the wei-ya a retrofit chassis? In which case I guess somebody had to hook it up to and old tube...

 

[gridrunner]

I have to say it looks like a wierd CRT fault to me. I've seen wavey lines, shrinking screens and other strange distortions but a rounded patch on the tube - that is odd.

 

[Paul_in_nottingham]

This happens on my new Xenon as soon as I switch it on. Not fussed about it as it only lasts a couple of seconds. Monitor is a Hanty MTC9110.

Curious as to what was causing it.

 

[joe34]

the original poster has now fixed the problem, turned out to be the following below (to quote him):

the problem was in yoke of 14ohms, which was not compatible with the monitor that requires a yoke of 36ohms or more... thanks to all by help.
(my english is bad...)