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Digital Group video monitor has horizontal bands

J

johnx993

Experienced Member
Joined
Oct 26, 2008
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242
Location
Texas (mostly)
I'm not much with analog video, but I've got a DG monitor that has slowly marching horizontal bands on the screen.
The screen is readable, the bands are just a bit dimmer than the rest of the screen.
My gut tells me it's a capacitor problem, but I'm not sure how to approach it.
Any suggestions?
 
Just for the avoidance of confusion, do the bands run from left to right of the monitor and drift up or down over time?

If so, my first assumption would be mains 50 or 60 Hz based interference. In this case, the most probable cause would be in the power supply section.

Have you located the schematics for this monitor?

Dave
 
The input is, IIRC, 75 Ohm coax from a DG Z-80 box.
The bands drift upwards slowly.
It had been working properly for years, then just started showing the bands recently.
I have the original systems manual for the machine, and it seems to have schematics for everything except the monitor.
The monitor is in the usual brown/beige Digital Group housing. But there is a word "Javelin" on the face.
I assume that's the original manufacturer, resold by DG.
And, BTW, it looks like they are still making display equipment.
-J
 
That sounds like a smoothing capacitor on one (or more) of the low voltage supply rails degrading to me.

You should observe some noticeable mains ripple (at either the mains supply frequency or twice the mains supply frequency) on one (or more) of the low voltage supply rails.

Dave
 
johnx993 said:
The monitor is in the usual brown/beige Digital Group housing. But there is a word "Javelin" on the face.
Click to expand...

Interesting. My Digital Group monitors, and all pictures that I have seen, are Sanyo VM4209 models. Can you post a pic of yours? It might help with identifying the specific model.
 
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