Check RGB from board using voltmeter?

[Witchboard]

I'm troubleshooting a color problem on a monitor and have checked and replaced everything up to an IC.  I want to verify that I'm getting color output from the board.  If I don't have a secondary monitor to test with, does the RGB coming from the board provide any current I might be able to check with a voltmeter to verify that there's a signal?

[grantspain]

is your problem a colour missing?if so we have to decide if its game board or monitor-the way to prove that is very easy.say you have no red,well all we need to do is swap input wires on the rgb,if you still get no red by swapping the red for blue then its prob a monitor fault otherwise its a board fault,but if you want to meter inputs then you should be looking for 5volts on each colour input,again if thats missing then its a board or wiring fault otherwise monitor.post me some more info on what your actual fault is,of course in electronics elimination is the key.

[Witchboard]

It's not possible to switch the RGB inputs unless I remove the pins from the connector, or cut it.  I'll see if the board is the issue by checking for the 5V.  Appreciate the reply.

What do you suggest I use as a ground when testing these?  I tried using the monitor frame since it was convinent, but I'm not getting readings from any colors by doing this.

[SirPeale]

It's not possible to switch the RGB inputs unless I remove the pins from the connector, or cut it.  I'll see if the board is the issue by checking for the 5V.  Appreciate the reply.

So remove the pins.  Should be just a matter of slightly bending back the stop pin and pulling it out.

Or if you have a bunch of alligator clips, just use them from your harness (though I'm sure you don't).

[Witchboard]

I already moved the pins in the connector.  I'm having a problem with green, so I swapped the green and red.  On the boards hardware test, it shows green, red, blue and white, with the names above to identify them in white text.  The red showed up in the green column, but the red column was black, where it should have been green.  I don't see how this determines if the board or if the monitor is bad, since if the monitor isn't displaying green, then it won't show green regardless.  If the game board is bad, then it won't show green regardless.  I guess I'm not following with the whole pin swap thing.

[grantspain]

it can be a bit confusing,your gameboard does not really know that your colours are red/green/ and blue,what it does is send a signal at about 5v so if you get 5v from each colour output then this pretty much proves your board is ok,if you diss all your colour wires off your chassis and use one to prove which colours are working,for instance use the red input wire and put it in place of each colour position on the signal input plug-you should get each colour come up,if one is missing then its a monitor or tube fault-once you have proved this we can progress to the next stage.

[Witchboard]

what it does is send a signal at about 5v so if you get 5v from each colour output then this pretty much proves your board is ok

Where do you suggest I ground the video signals to check for voltage?  I tried the monitor chassis frame, but didn't get anything from any color.

if you diss all your colour wires off your chassis and use one to prove which colours are working,for instance use the red input wire and put it in place of each colour position on the signal input plug-you should get each colour come up,if one is missing then its a monitor or tube fault-once you have proved this we can progress to the next stage.

If I understand the above statement, then I've already proved the green is bad on my monitor since I swapped the red and green and the green still did not display.

I guess I'll start from the beginning.  I'm working on a WG K7400 monitor that's not displaying green.  I've already done a cap kit, replaced the transistors and verified the resistors in the circuit to be good.  I checked the trim and color cut-off pots to verify they work as well.  I've basically troubleshot all the way to the IC and before ordering a new one, I thought I would verify that it wasn't a problem with the game board.  I've not had a monitor have a bad IC before, but I guess there's always a first time for everything.  My biggest fear is that the tube is shot.

[Ken Layton]

This is an instance where a rejuvenator would tell you immediately if the tube has a problem. BTW, is your tube a Zenith? If it is then it's got a problem. Zenith tubes are failing prematurely and have a much higher than normal failure rate.

I did a tube swap on a k7000 last summer where I swapped in a tube from a Magnavox 25" console that was sitting 'on the curb' for free. The tube swap was very successful!

[Witchboard]

I'll double check the tube when I get home and report back.  I can't recall at the moment.

[grantspain]

to meter use your psu common for your negative lead,does sound like your tube but worth checking your pins on the neck,broken track,or open circuit transistor.

[Witchboard]

Yes, it's a Zenith tube.  I have the most horrid luck with monitors.  Did you have to do a yoke swap as well with your replacement tube Ken?

I'll try to verify the board is outputting green by tracing the ground on the PSU to the edge connector.  It's a Neo-Geo 4-slot so it doesn't have a Peter Chou style unit, but one like a computer.

I've verified that all the colors are working off the board.

[SirPeale]

Have you checked the color transistor on the neckboard to make sure it's still good?

[Witchboard]

I've replaced both of the transistors in the green circuit on the neckboard.