Isolation Tansformer Fun

[CRiMiNaL]

I just bought a bartop arcade machine with a 9" Hantarex MTC 9000 Monitor inside. When I bought it the guy took out the ms. pac-man board and the power supply. I knoticed there was no isolation transformer present. The guy said you don't really need one, they are just for safty. and he twisted the two ac wires to the power cord and the monitor did power on......so I go home and hack a vga cord and plug it into my computer, turn the monitor on and bang!....I blow a fuse in the montior. so I replace the fuse and this time I turn the computer and monitor on the same time and while they are on I connected the vga cord to the video card and BANG. Now the video card and mother board are fired....

So I'm guessin the reason why is because i needed an isolation transformer hooked up......but its weird the ms. pac-man gameboard didn't need an isolation transformer, it worked fine with out it.  but I can't get the monitor to hook into the computer with out sparkes flying.....

this isn't the first arcade i'd wired with a computer in it so I know everything is wired right....but this is the first time i've tryed hookin a computer to an arcade monitor with out an isolation transformer...


So do i need an isolation tansformer?

[StephenH]

Yes, It sounds like it needs the isolation transformer.

[SirPeale]

That is weird that it would work at this guys place and not at yours.

[CRiMiNaL]

I can plug in the arcade monitor to the wall without an isolation transformer and it does power on.....and i can plug it into a gameboard with no problems.....   but as soon as i plug the video into the computer BANG!

[woodygjw]

I can plug in the arcade monitor to the wall without an isolation transformer and it does power on.....and i can plug it into a gameboard with no problems.....   but as soon as i plug the video into the computer BANG!

Its probably because the monitor is not properly grounded.  As soon as you connect your video cable to the computer, it is then probably grounded through the computer, shorting out your chassis.  Put in an isolation transformer and I think your problems will go away (and prevent you from damaging anything else since it still seems to work with your game board.)  Also check to see that your monitor is properly grounded.

woody

[Rickn]

Ok here is a little on this...
First off power is usualy delivered to a small business, residence from a transformer at the road.
This transformer delivers 240 volts  from a centertap transformer. Check your fuse/circuitbreaker panel. You will find 2 rows of fuses or breakers (left and right side).

Only if you are qualified (If so you already know)- if you were to open the panel further - you will find that "Black wires" are connected to the breakers and fuses. Left side is opposite polarirty from right side. These are the hotside.

The white wire is the return.

Also there is a ground.

Bottom line, the reason the monitor worked as shown, both the game and the monitor were connected to the same side of the fuse panel and the power plug on both the game and the monitor were of the same polarity.

If the monitor does not have an isolation transformer or is not a switch mode supply use an Iso Transformer 150%.

If the monitor is switch mode- you are ok.

Hope this helps.

Rick Nieman
Nieman Video Displays
Nieman Displays.com