Newb looking for fixit advice.

rpgposer

New member
Joined
Apr 22, 2010
Messages
91
Reaction score
2
Location
Lancaster, Pennsylvania
Hello,
I recently acquired a Midway Strike Force conversion cab. I am guessing it's been in someone's home, since the cab itself is in good condition and the game is set to free play.

The board powers on and can be played blindly, but of course, no video. The monitor doesn't crackle, and the heater filament doesn't glow. If I unplug the board from the jamma harness and dc power supply, the monitor appears to fire up, it crackles, the heater filament glows and there is static on the tube.

I have checked incoming AC power to the filter and all fuses with a fuse checker.
Is this some power/circuit issue, or is something tripping some sort of failsafe turnoff on the monitor when the pcb and monitor are both powered on?

Thanks for any help.
 
Do you have power to the monitor when everything else is plugged in and powered up? There should be a small two position molex connector hanging off of the monitor chassis that you can seperate and test for power. If you have power to the monitor you need to figure out what monitor you have and test for B+. This site has pictures of monitors you can compare your chassis to:

arcadecontrols.com/BBBB/monitor.html

 
as always it is good to change out the caps with a cap kit. You can get them from alot of places like bob roberts. I would also check the diods (bridge recitifier) depending on the monitor there should be 4 diods. also, check the flyback for a dark crack or ay dammage. if there is no high voltage then there will be no glow or crackle.
Just my 2 cents.
 
Look over all of the wiring and test voltages, something is fishy if the monitor works when the board isn't hooked up but doesn't work when it is hooked up.
 
Look over all of the wiring and test voltages, something is fishy if the monitor works when the board isn't hooked up but doesn't work when it is hooked up.

Yeah, something IS fishy here... logic dictates that if the monitor chassis had a major problem, like flyback (no cracks, no smell, no arcs), it wouldn't power up at all, even without the board and 12v power supply disconnected.
The power cord in needs to be replaced. I will test incoming power before and after, then work my way back.

Wish me luck.
 
Update.

Have replaced the power cord. Original was worn and had the ground plug snipped off. Dusted monitor chassis and cleaned the JAMMA pins on PCB. Disconnected board and 12v power supply from the harness, powered on and got 132VAC coming into the AC filter. Disconnected incoming AC molex to monitor and tested from the molex, got the same reading.
Connected everything, tested incoming AC to 12VDC power supply, got 132VAC. Tested outgoing DC, got 13.85VDC, was able to turn it down to 13VDC with the adjusting screw.
Still nada video, no filament glow. Disconnecting the board and power supply via the harness, monitor appears to power up, have filament glow, very minor crackling like a typical monitor warming up, can feel typical static on the screen.
As far as replacing caps goes, that is done when there are various issues like blooming and bleeding, correct? This monitor has burn in, but none of the video effects from old caps.

I think my lack of basic electrical circuit understanding is an issue. Has anyone experienced something like this before?

Thanks.
 
You need to identify which monitor you have and then find the manual, mopst are located here: http://arcarc.xmission.com/PDF_Monitors/

Then, with everything powered up you need to check the B+ on the monitor chassis and verify that it is not too high. If B+ exceeds a certain voltage level the monitor will shut down the high voltage in order to avoid producing x-rays from the picture tube.
 
You need to identify which monitor you have and then find the manual, mopst are located here: http://arcarc.xmission.com/PDF_Monitors/

Then, with everything powered up you need to check the B+ on the monitor chassis and verify that it is not too high. If B+ exceeds a certain voltage level the monitor will shut down the high voltage in order to avoid producing x-rays from the picture tube.

It's a WGK7000 series. K7610 to be precise. By not having the board and PS harness hooked up while powering on the cabinet, was I bypassing a safety lock?
OK, back to the problem... I have looked at the WG official troubleshooting form and schematics. I will be testing voltage off an IC leg? IC #4? Can't even see that IC. I'll keep looking.

Thanks for your help.
 
The easier place to check is the large white resistor behind the flyback. It is resistor R301 and the B+ should be present on the back leg of the resistor, usually a blue wire goes to this resistor.

I doubt you bypassed an interlock with the board and ps not hooked up but it is possible that one or the other is shorting out the AC power for some reason. Is there more than one wire going to any connection point on either component?
 
Back
Top Bottom