What causes vertical banding on black and white sets?

[Devicemodder]

I have a 3.5 inch black and white set, sold as an Action SportVision, model no. ACN-3500. it has some vertical banding when displaying a white screen. what causes this and is there an easy fix?

Also, I notice that there's a bit of what looks like geometry issues along the sides of the set. how would i fix this?

[zeno]

You will need a schematic ! There is a common problem on most set that
cause "jail bars" but this is different looking. Add in the other
problems & you may be looking for a power supply problem.

73 Zeno
LFOD !

[Electronic M]

In general what causes it is an unwanted signal that is a whole number multiple of the horizontal scanning frequency showing up in the horizontal, video stages, CRT gun, or power supply.

[Devicemodder]

Originally Posted by Electronic M

In general what causes it is an unwanted signal that is a whole number multiple of the horizontal scanning frequency showing up in the horizontal, video stages, CRT gun, or power supply.

Any easy fix?

[Devicemodder]

Originally Posted by zeno

You will need a schematic ! There is a common problem on most set that
cause "jail bars" but this is different looking. Add in the other
problems & you may be looking for a power supply problem.

73 Zeno
LFOD !

Can't find a schematic for the set anywhere, not even a sams manual. I did find the video/audio out from the tuner, and if it's disconnected, i get retrace lines.

I have seen these lines/bars/whatever on another set of mine as well. I am starting to suspect power supply.

[Electronic M]

Originally Posted by Devicemodder

Any easy fix?

If you have the schematic and are good at using an oscilloscope it could be.
Exact cause varies from set to set this why you need a scope to hunt it down if it's internal to the set.

If you are using an internal power supply and that supply gives the same problem with multiple sets try another supply.

I don't mess with solid state stuff much, but any supply that doesn't use a 60Hz transformer is not something I want to use. Most switch mode supplies create RF noise and most switch at horizontal rate (the switch mode supply concept was developed by Motorola for TVs in the 70s thus the reason it often uses TV horizontal rate) and create noise at multiples there of.

[Devicemodder]

This set uses an external 7.5VDC wall adapter. And its not a switching supply, it's the older 60hz transformer fed into a bridge rectifier.