WG K4900 Wave?

[Bender]

I have a WG K4900 in a tron cabinet

I recapped it and got the picture to look pretty good but I still have the phenomenon that looks a lot like when you watch video of an arcade monitor you can see the sync cycles go by, not sure what to call it really a "wave"? I'm a little hesitant to call it a wave because there is no real geometry distortion only a slight intensity difference that moves across the screen, the monitor is in the vertical position and the "wave" moves left to right

I think this may be a power issue but I'm not sure where to check the B+ and I don't think this monitor has a B+ adjustment

any input would be greatly appreciated

Thanks!

[grantspain]

could be an earth issue

[Bender]

could be an earth issue

Could you explain that a little more?

[ed12]

from what i can read the wg4900 has no voltage control :dc: side
i would chk chassic ground
rem this monitor need's to be isolated
most important

ed

[grantspain]

you should check the earth from your wall socket has continuity onto the power supply,monitor frame and any exposed metal parts of the machine
if you have a switch mode power supply you can try to link the earth to ground

[ed12]

here >http://www.mikesarcade.com/arcade/monitors.html<
use firefox,it want's it, u will find both schematic's for that series there

regards

ed

[MonMotha]

This usually does indeed seem to be an ground (earth) related issue.  It sometimes helps to add or remove, as appropriate, a link between DC power common ("ground" aka the black wire) and earth ground (the green or green/yellow wire).  Also make sure that the monitor frame is connected to earth ground.

I've also had this be an issue with a faulty AC bulk smoothing cap right at the input on the monitor before the regulator; this cap is generally not included in "cap kits" as it doesn't go bad as often and is big and expensive.  A bad cap at the output of the B+ regulator could also be a cause, I guess, but these usually are included in cap kits.

[boardjunkie]

Hum bar is the term for what you have there. I hope you checked for cracked solder while doing the cap kit.

Anyway, I've seen this issue in games caused by dirty fuseholders and/or fuses.

[ed12]

boardjunkie i was thinking hum-bar
but the nick states

>distortion only a slight intensity difference that moves across the screen, the monitor is in the vertical position and the "wave" moves left to right
<
that put's me in mind of a crappy ground somewhere >cold solder joint's<
and or a leakey by-pass
1mf or less cap

ed

[Bender]

Thanks everyone!

Weirdest thing...
I'm messing around with the 5v pot on the PS cause I'm trying to get a NVRAM back-up for the high scores to work and discovered if the 5v is turned all the way down which is about 4.8v there is no Hum bar, the monitor looks rock solid (but said NVRAM backup does not work)
I didn't even think the 5v was in any way connected to the monitor

There is an earth ground to the monitor frame
a ground strap near the coin door isn't connected to anything, anyone know where that is supposed to go?
seems like there is some weird electrical thing going on some where in there
how do I test this stuff to try to isolate the problem?

Any ideas?

[Bender]

Sorry to bump this but, I could use some help on how one would test for ground/earth issues

Thanks!

[grantspain]

Sorry to bump this but, I could use some help on how one would test for ground/earth issues

Thanks!

multimeter set to ohms and then meter every earth connection or metalwork back to wall plug-expect a range of readings due to resistance but you are aiming between 0 to 5 ohms

if all that checks out then post a photo of your power supply