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Main => Monitor/Video Forum => Topic started by: Grauwulf on May 07, 2005, 06:00:53 pm

Title: K4900 Vertical deflection failure
Post by: Grauwulf on May 07, 2005, 06:00:53 pm

I have a K4900 monitor that I have a vertical deflection failure on. I have replaced or tested all the usual suspects, both os the vertical output transistors, R313, I've done a cap kit and I've tested and replaced the vertical adjustment pots. I have also replaced IC301. All of this has made no difference at all.

This monitor had the focus grid wire from the flyback shorted out to the v-pos jumper wire when I got it. I have patched both wires back up and replaced the fuse. The band it is showing on the screen is a little wider than I would expect to see from the standard vertical deflection failure as weel. Anyone have any suggestions as to where to look next?

Title: Re: K4900 Vertical deflection failure
Post by: Ken Layton on May 07, 2005, 11:12:36 pm

This sounds like a job for an oscilloscope!

Title: Re: K4900 Vertical deflection failure
Post by: Grauwulf on May 08, 2005, 07:51:35 am

I have one here that I was just given, but I'm not sure what I'm looking for, or where to look.

Title: Re: K4900 Vertical deflection failure
Post by: Ken Layton on May 08, 2005, 11:51:32 am

Wells-Gardner monitor service manuals usually give actual pictures at certain points on the circuit board of what you should be seeing on the scope. It even says below the picture the settings your scope should be set to.

I'd start by scoping the outputs from the IC.

Title: Re: K4900 Vertical deflection failure
Post by: Grauwulf on May 08, 2005, 12:52:27 pm

Thanks Ken, that gives me somewhere to start. This is the second K4900 I've run across with something shorted to the v-pos wire. I don't know how people manage to do it.