Constant horizontal 'brightness'-line on a hantarex (probably mtc9000) of 1991

[trick72]

Hi,
The included picture tells it all. The screen seems to be "divided" by a constantly moving horizontal line. The line moves depending on how bright the screen is. Above that line, the picture is brighter than below the line. But as I already mentioned, this line is not always at the same place. During games where there is more white or light colors (when the screen is brighter) the line moves more to the bottom of the screen. When I manually increase the brightness of the screen, the line also shifts more to the bottom (so the upper, bright part of the screen expands). So that line constantly shifts up and down during a game, depending if the screen itselfs is darker or brighter and this is very annoying. Any ideas if this is fixible?
Thanks

[grantspain]

could be the screen volts too high therefore giving some kind of flyback lines
could be the start of a frame collapse
could be an earth/interference fault

1-disconnect the video signal to see if you still have the lines
2-if you adjust the height(vertical size) smaller do the lines start to disappear
3-check the earth continuity to the wall plug

[Ken Layton]

And this is after it has had a fresh capkit?

[grantspain]

mtc9000 did suffer from cap failure frequently,very likely a cap kit would fix this problem like ken said

[trick72]

It did not had a cap kit yet , so I'll try that. thanks

[qrz]

a failing vertical output ic can exhibit this very symptom   


qrz

[smartbomb2084]

I'm curious, you don't specify what game or what video process is driving the screen.  This looks like a power/ground problem as if a filter cap of some kind has gone bad letting in a hum bar.

[qrz]

This looks like a power/ground problem as if a filter cap of some kind has gone bad letting in a hum bar.

when fatigued, the vert output ic can pull a higher than normal current. the additional load may cause
 the vcc (typically 24volts)  to drop .

this lowers the boost/return cap voltage . which, in turn , reduces the deflection height and may cause
foldover/vert retrace.

and yes...., a leaky diode /cap in the ic's vcc supply may cause this symptom. and thus, should also be checked.

qrz

[Aliphina]

Hi, i know this is an old post now... But am interested in what advice i can get.

Firstly. Did the information before fix the issue?

Reason is, I have the exact same problem!!

However i have just had a new cap kit installed and replace the IC1 chip.

Where do i go from here?

Thx
Nathan