Video problems...

[Totallyout2lunch]

I just picked up a jama cam from a bloke down the road. I saw it working, so no worries or so I thought.

I got the cab home, put in a fav PCB just to test you understand, plugged it in, and it seems that the monitor has got buggered.

All i get it a white spot in the iddle, with a few flickering colors in the spot. I can hear the game in action if I hit the Player 1 button, it all seems to be ok there, so what is the problem with the monitor.

Monitor is a Samsung 20' (ish).

[Ken Layton]

Was the monitor securely bolted down when you moved the game to your place? Could any small pieces like screws or nuts have fallen on or under the monitor's main circuit board? If you tap the metal frame of the monitor with a screwdriver handle does the picture suddenly come back to normal for an instant?

[Totallyout2lunch]

Yes the monitor is securly fastened, it hardly moves if I push the frame. If I wobble it the dot dissapears sometimes, but I have not seen it come to full screen.

There is enough space under the circuit board for a screw not to touch the rest, but I will check again.

Which part do you want to tap with a screw driver? I'm a little uncertain, as I am not sure which parts are the really dangerous bits!!!

Cheers.

[Ken Layton]

Just tap lightly the metal monitor frame anywhere with an insulated handle of a screwdriver or the wooden handle of a hammer. What you are doing is seeing if the vibration causes the picture to come back on for an instant. Chances are your monitor may have some bad solder joints.

[Totallyout2lunch]

I have given it a good few taps, and not much happen, sometimes the white ball moves a little, but thats it, no full picture.

I would guess that its dead? Is it worth geting a professional in to look at it, or just buy a new one from happs?

[MonitorGuru]

It sounds like your yoke wire became detached... Either directly on the circuit board (most likely) or on the yoke itself.

This would cause both a horizontal and vertical "collapse" where you only get a bright dot in the center of the screen instead of a normal raster.

Be sure NOT to run the monitor very long (like only a few seconds) like this, otherwise you will end up buring in a horrible brown spot in the middle of your screen as nothing is deflecting the electron beams across the screen.  Technically you are probably buring that point well over 77,000 times faster than the rest of the screen (240 vertical rows * 320 horizontal columns), or 1 minute on = 2 months of normal never-turned-off use.

Look for a grey plug with a Red, Yellow, Green and Blue wire running from the copper windings around the back of the tube (the yoke) plugging onto the main circuit board.  If it's off the connector, press down securely (with the macine UNPLUGGED).

If its on, then, as Ken mentioned, take something totally insulated (like a piece of cardboard) and press against the connector and see if the screen comes back momentarily with the monitor on. If so, you will have to discharge the monitor and remove the board and resolder the pins which probably have cracked their solder joints from moving.

[Totallyout2lunch]

Thanks for the help...

<slaps himself around the head>

I have found a cable that was not conected correctly, plugged it in, and it now works fine. Its the one thet connects to the board, so you can put it in slot 1 for screen to face one way, or slot for a 180degree rotation.

</slaps himself around the head>

[Ken Layton]

Sounds like you found the yoke connector alright. Glad it's working.