Dual monitors fail at same moment after grounding change (friggin nuts)

[Pipercub]

OK, I have a Playchoice 10 with two 19 in. monitors. The game had been converted to a Jamma cab and I had just finished stripping it and converting it back to PC10. The game worked great and the monitors were fine other than light burn in on one of them and some faint hum bars on both.

I made two changes to fix this minor fault. The monitors had a two wire power cord and in the original scheme the two monitors were grounded together as was the control pannel, board shield etc. All of this harness was missing except the monitor to monitor ground strap. I replaced the cheap power strip with a good heavy duty one that had ground prongs. I plugged in the monitors, power supply, lamp etc. to the new power strip. Then I ran a ground wire from the monitors to the board shield and then to the ground prong of the power strip using 12 guage wire and a plug. The ground wire was secured to each location and not touching anything else. The power strip was plugged in and I heard a POP. I unplugged it right away and then recconected everything without the ground and the monitors powered up with very visable hum bars on both and the top monitor looked like it needed to be degaused. I powered them down for a few then powered them back up and there was no response at all from either one. I pulled them both and one of them had a blown AC fuse, replacing it had no effect.

What I know so far.....

Checking the first monitor there is no DC present after the power supply. I haven't had the chance to check but I bet the rectifiers are toast. Simple fix there. Of course after that if there is other damage........ And who knows about monitor two.

The ground was to the monitor frame and was no different than the Nintendo ground wich aslo ran from the frame to the ground wire for the AC plug. I do not believe the monitors were "hot" because I had touched them many times (the metal frames) and never got a bite.


Any idea what the hell happened here?

And anyone have any PC10 monitor parts laying around if I need them?

[tom61]

I think you just plugged 2 Nintendo monitors directly to 120Volts, right? Nintendo Monitors are 100Volt, you probably just fried them.

[Pipercub]

The cab had been converted to Shinobi and had been running off 118v since 1991
with coin collection records going for ten years so it wasn't that. An 18% overvoltage should
not be such a big deal. Something has been modified in the wiring harness where there is now
a path to ground that shouldn't be there. I am thinking it might be somewhere in the audio section
because those connecors were cut off. Another day though. I am still trying to find the time to replair the
first set of issues.  

[Edgedamage]

Mabye this might help sometimes the monitor frame will pinch the degaussing coil causing a short.

[Pipercub]

Good news and bad news. Monitor one lost all 4 diodes in the bridge rectifier and a 7 watt ceramic resistor, fixed now. Number two lost the same resistor and an inductor package. Unfortunatly the values aren't present on the schematic or board, so now I have to pull the bottom one out and pull it apart again to desolder the inductor package and see what value they are.


Maybe I was unclear in my post when I said that the cab had been converted and running with both monitors on a powerstrip since 1991. The monitors had been runing plugged into a regular powerstrip since 1991. The difference in voltage had beed present for 12 years of opperation. What I did was restore the ground system that had been stripped from the cab. In hindsight it is clear that the ground had been stripped from the cab because the isolation transformer had been removed.