Monitor dark patch in top left corner

[PhilT]

Hi

Put my Outrun back together and am now chasing down faults, on the monitor it has a darker patch in the top left corner, wondering if any of you gurus can point me in the right direction to fixing it.

The monitor had partial vertical collapse, picture was about 1 third height, so has had all caps replaced, along the way I discover a broken choke coil so 2 of those got changed too and I reflowed solder on all header pins.

I havnt spent a huge amount of time trying to 'dial it in, it was way off, screen cranked way up etc so I guess someone tried to fix it by messing with all the adjustment pots previously to the cap kit being fitted. I have got it in the ball-park and it fires up fine and is solid but has this dark patch, its more pronounced on certain colours. Those solid dark lines across the middle and bottom are just a trick of the camera.

Degauss circuit is fine and I have tried that several times, makes no difference and theres nothing around it that would affect the screen.

One thing I noticed when trying to adjust things is that the red gun pot is set way lower than the blue and green, is that an indicator of a problem perhaps, i just dont know.

Any ideas thanks.

Phil

 

[Bods]

I would think it's just issue with Degaus still. All depends where the machine has been previously, if it's subjected to any strong magnets

Say you have a TV thats not moved from the same position in years, it will be fine even if the degause circuit has stopped working, soon as you move the TV from that position it will change due to the Earth Magnetism, then it needs to be Manually Deguased with a Wand. Some take quite a bit to demagnetise them and get the colour perfect again, so it may need doing manually even if the built in circuit working

one thing to check is the Degaus wire around the back of the tube is at the edges of the tube, should be fixed near all corners, it's usually seen worse on screen with Red, Green or Blue being the primary colours used, you can use the tests on the game board menu for monitor test to bring up the colours

Not much you can do sometimes without wand

 

[iamjimmi]

I have had a similar issue with a monitor that had working coil surrounding the monitor.

A handheld wand sorted it.

It was if the internal coil just didnt have enough oomph (technical term).

Definitely worth a try...

 

[PhilT]

OK thanks guys, I was concerned it might be something more serious. First time I have poked around in the guts of a monitor so just happy I didnt break it. Any idea where I can get a wand from
Phil

 

[Bods]

Like the Flybacks it's another thing no one sells now in the UK due to lack of CRT's

from reading old posts, what a nightmare this is all getting

Just talk of cheap chinese ones that don't last long. where are all the ones all the TV repair places used to have, all been dumped, seems you need to live in the USA now as they always have everything

Not sure where to go for em now

 

[iamjimmi]

I got mine from the states...

If u live near Leeds I might be able to swing by with mine....

 

[big10p]

I've heard talk it can be done using a power drill or soldering iron. Never tried it myself, though. Some googling will probably turn up the goods.

 

[RolyRetro]

I used a magnet from a speaker to Degauss, took a bit of practice to get the right angle but worked a treat on my monitor.

 

[andrewsm]

deguass is simply a coil with AC passing though it so you get a fluctuating magnetic field. Speaker magnets are polarised so you could end up magnetising the tube the wrong way.

 

[PhilT]

@iamjimmi thanks for the offer, I am going to leave it well alone for the time being until it gets moved to its permanent resting place, maybe it will sort itself out in the meantime. If not out comes the electric drill