WG 19K4903 monitor problem

[pinhead0101]

Hi.  Just purchased a Moon Patrol.  Thing worked great at the auction and image/color were excellent.  got it home and monitor is black!  in following a flowchart I found online, I got to the point where it asked if the tube heater was glowing - it's not.  That's kind of where I'm at.  The marquee and coin door lights work, I'm getting power to the monitor (110vac) and the game will register credits and work, just no images.  It does sound like the tube is whining, but I'm not seeing anything at all on the screen.  I'm great at pinball repair (electronic and other), but CRT's are gonna be new...
I'm not having a ton of luck finding repair tips on this sort of thing.
thanks to any who will respond.

[grantspain]

dry solder joints on the monitor chassis or power supply voltage missing

[pinhead0101]

Thanks, when you say power supply voltage missing, which do you mean? 

[grantspain]

the power supply for the game board,maybe the +5volts is missing

[pinhead0101]

k

[grantspain]

well you need to look at the basics,the cab worked when you collected it but now it don't(although you know you got power because the marquee lights up) so there are two easy steps to make to prove where your problems lies.
1-switch the machine on and add a credit,do you get game sounds?if yes then the fault is either the monitor itself or a break in the monitor signal.if you don't get game sounds then almost certainly the problem lies with the power supply thats runs the game board.
2-take the back door off,look at the neck of the t.v tube-can you see a glow of orange?locate the flyback transformer(the big plastic component with a fat red wire that goes to the top of the tube)where you will find a focus and a screen volts pot,turn the screen volts up a little-if you get a whitish screen then the monitor is almost certainly o.k-if you don't then you need to check the monitor board for bad solder joints.
i am guessing "k" mean't "what"

[pinhead0101]

k meant ok.  game does work, credits, sounds, actions and yes, crashes too!  just can't see it at all.  no activity on monitor.  no glow at neck, focus and screen pots have no effect.  i have 115v supply to monitor, and i had a flowchart for 4900 series monitors that led me through checking voltages at 2 resistors and got me to "is the heater glowing?" - it's not.  then it said check the resistor r416 (2.2ohms)  it's ok, and the solder joints on the neck pc board all look really good (shiny and the like with no cold joints or cracks)
there are no obviously failed components and the fuses are all good.
thanks!

[modessitt]

Read up on how to safely discharge a monitor before working on it.  Discharge before every time you touch anything near the tube or anything connected to the tube!

It is not uncommon for a game to be moved on a truck, then suddenly have problems.

Since you say the monitor has 110VAC at the connector, then we'll assume the problem is in the monitor.  I would first check the fuse on the chassis and make sure it is good.  If not, change it and power up to see if it blows again.  Next, do what Grant said and try turning up your brightness control on your flyback.  Also, make sure all your connectors are plugged in securely (power connector, degauss wires, yoke wires, anode wire, and video signal wires).  I have seen some older WG's that won't power up if the degauss wires aren't plugged in.

I guess it's possible for the monitor to decide to die right when you get it home.  If you're used to working on pinball sound boards and driver boards, then you should be used to testing and changing caps and transistors.  Safely discharge your monitor and replace all the electrolytic caps.  Follow Grant's advice and scan the board for cold solder joints, especially around the high voltage and power supply areas.  Also, follow your flowchart and check your high-voltage-shutdown circuit for a bad transistor.  You may even have to change your Horizontal Output Transistor.  I hope it's not your flyback, as they are hard (if not impossible) to come by for the K4900's.

Check the easy stuff first, then do some basic troubleshooting using your flowchart.  Once you've been able to rule out some items, let us know what is going on.

[pinhead0101]

gives me plenty to get started - thanks for the help gang!

[Ken Layton]

The 4900 series is well known (as other Wells-Gardner monitors too) for tons of bad solder joints all over the main board. If this monitor is still running on it's original electrolytic capacitors then it's certainly overdue for a capkit.

[pinhead0101]

sounds like that's the way it's going to be...i buy all my pinball electronics from great plains or big daddy's - does someone offer various component kits for monitor models?

[modessitt]

Zanen Electronics and Bob Roberts both sell cap kits, and often include transistor replacements as part of the package.

[pinhead0101]

cap kit is enroute - let you guys know how it turns out
thanks for everything....so far....

[pinhead0101]

update:  replaced the electrolytics on the board, and while reassembling, noticed a crack in the neck pc that ran through traces.  My guess is the traces were making contact at the auction, then shifted enough when bringing it back home to lose contact.  probably didn't need the cap kit, but what the hell, they're all new now.

[grantspain]

glad you fixed it,well done