4900 Question

gregr

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balitmore, Maryland
Just finished recapping a newer version of the 4900 and everyting looks good except that I can see what looks like a retrace line (very faint) that that scrolls vertical. I have tried adjusting the the black level to see if it disappears but it is still noticable.

Anyone experienced this or have any ideas?

Thanks
Greg
 
The Blanking circuit is in the IC 301, it comes out of pin 17. The caps that are attached are 303 and 301.

Check around there and see if there's something wrong, or if you can replace that Old IC.
 
4900 Update

Replaced IC 301 with a new chip check, check the solder joints around C301 and C303. The picture is solid but I can still see the line scrolling vertically. I also checked that the tube and yoke were fine by testing 2 other chassis.

If I follow the schematics from pin 17 of IC301, it is a direct line to the flyback with a few resistors and capacitors in line.

I'll check the resistors and capacitors but could the flyback be the issue.

Thanks
Greg
 
This is why you need to respond to ALL responses for info, instead of just the one with technical advice.

The reason I asked what game it's connected to, and another person asked for a pic, is because the problem may not be due to the monitor (like hum bar). It still might, but we need further info to be sure - and can't give specific help until we get it.

You'd be surprised how many people misdiagnose their issues. I've seen threads go over 30 posts in the wrong direction because nobody asked a few simple questions first...
 
This is why you need to respond to ALL responses for info, instead of just the one with technical advice.

The reason I asked what game it's connected to, and another person asked for a pic, is because the problem may not be due to the monitor (like hum bar). It still might, but we need further info to be sure - and can't give specific help until we get it.

You'd be surprised how many people misdiagnose their issues. I've seen threads go over 30 posts in the wrong direction because nobody asked a few simple questions first...

Amen, brother. I've chased my tail too many times to skip the basics.
 
4900 Questions

I'm testing the board with a pattern generator, as for a picture, I tried to take a picture but the issue isn't visible in the picture.

Hope that helps.

Thanks
Greg
 
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