image on monitor is rolling over on sides

vreelander

New member
Joined
Mar 28, 2012
Messages
3
Reaction score
0
Location
Exton, Pennsylvania
I just pulled a 13" monitor from a 1981 Donkey Kong cocktail cabinet that i have, which along the sides the image is "rolling over" as what my friend i and called it. Basically its like the images that are going off screen are folding over on top of whats already showing. Haven't done any monitor work before but do have some experience in soldering and circuit boards. Seeing if someone could get help figure out what is going on/what needs replaced/etc. . Thanks I appreciate it. :)
 
Nintendo monitors (Sharp, Sanyo) have an issue called "Foldover" where the image curls on top of itself. You can almost always fix it by doing a capkit. Order a capkit from www.TheRealBobRoberts.net and install it, it should fix your problem.

Now, you MAY be able to adjust it out with the vertical height control, have you tried that? (since the monitor is vertical in your cabinet, it does it on the sides, if the monitor was horizontal it would be the top or bottom).
 
yea we tried that too and it worked for a bit but its back. Thanks for the suggestion of the cap kit. Lastly, Where would i find the model # on the monitor so i know which cap kit i need to buy?
 
Generally the model number will either be silkscreened onto the PCB or printed on a sticker stuck to the side of the chassis. If not, take a pic of it and someone will be able to identify it for you. It's more than likely a Sanyo 20EZ.
 
It's most likely a Sanyo - just the 13" version. Slightly different from the 20" chassis, but pretty similar.

In the 20" monitor, the failure you describe is very, very, very common. It's caused by the electrolytic at C407. It's right near the flyback, and it's 10uf @ 160v, at least in the 20" monitor. It's been a long time since I've worked on the smaller ones.

I usually just replace all the capacitors while I'm in there, but, there have been times when the picture is perfect save for the foldover, so I'll just change the one cap.

-Ian
 
after much fun of finding it. It is a sanyo and looking on Real Bob's site, the board matched the 20EZ map. definitely thanks for the help. I have a new and great appreciation for all the you repair guys who work on CRTs. man they have a lot of screws :p.

and RetroHacker or anyone really. what does C407 technically control on the board? just curious, but I'll be happy to get DK back up and running again.

Kev
 
That cap is one of the ones in the vertical section of the board, it and all the other components in the vertical section together make the picture fill the screen vertically. If any of the parts fail, it won't do it's vertical thing right. Resistors usually don't fail, the transistors (on a 20ez) don't usually fail.. the only part in that section that usually goes bad are the capacitors. Over the years, they dry out and their capacitance fails. The way that particular monitor is designed, when the caps start drying out, it squishes the screen and makes it fold over on itself. Basically what you're doing is lowering the voltage going to the two deflection transistors. Since it's not getting the voltage it wants, it does weird things instead of stretching the image out like it's supposed to. That particular cap may get more voltage running through it or something, making it dry out quicker than the others (hence why the above poster mentioned sometimes he only has to replace that 1 cap).
 
Back
Top Bottom