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WG K7197 – New Chassis Issues – Advice?
Question from Chris: Hello! After watching many of your videos and finding them immensely helpful in my new found arcade hobby, I’ve run into a bit of a problem that I’m hoping you may have some advice on. I’ve been posting about the issue over on the Arcade Controls forum, and I’ve received various bits of advice already. I’ll include the link below, as there are many pictures, comments, etc in the forum thread that would be useful in explaining my issue.
The general the story: I picked up a Mortal Kombat 1 cabinet (with a Ultimate Mortal Kombat 3 board upgrade in it) and found immediately that the game played blind. Checking the monitor, I discovered that the chassis was completely missing. A friend suggested I try the Wei Ya universal replacement chassis (429H), which according to the seller works for both 25″ and 29″ monitors within the proper resistance ranges. I tested my yoke wiring and it was easily within range, so I ordered the chassis. After hooking it up and finding the monitor working, the chassis ended up blowing a resistor, capacitor, etc after 5 minutes of use. One working theory is that the chassis requires isolation, and my transformer is not properly wired (Midway wired it strangely I’m told).
If possible, could you take a look at the forum thread when you have a moment and let me know your thoughts? I’m trying to decide what steps I need to take next. There are numerous pictures, diagrams of the current wiring, etc. Thank you in advance!
Link: http://forum.arcadecontrols.com/index.php/topic,139621.0.html
Thank you, Chris
1 answer
Response from Jonathan: Chris,
Looks like you’ve gotten a lot of good help from Ken and several others in the arcade controls forums. Yes, it could be that the chassis power is not being isolated properly. The parts that blew seem to indicate a power issue with either the power getting to the monitor or the power supply section of the monitor chassis.
From your pictures, it looks like the left side of your power brick unit is being used as the isolation transformer for the monitor. The yellow wires look like the input from the AC cord and the purple look like the output. I would trace down the purple wires and make sure they are the wires supplying power to your monitor. While it’s OK to use that isolated power for other parts that use AC voltage in your cabinet, I would probably disconnect those other parts just to make sure that they weren’t causing interference with the monitor’s power. You might also unplug the monitor from the power supply and measure the voltage coming off that connector just to make sure that it is correct.
I know that Ken said that some MK cabinets were improperly wired so it might be easier to install a new isolation transformer in the cabinet and run the power to the monitor from it. Arcade Shop sells new isolation transformers which should work with pretty much any monitor chassis (including your Wei-Ya). They are usually pretty inexpensive (around $35 shipped) and pretty easy to install. You might be able to remove that power brick unit altogether if you get an isolation transformer seeing how you wouldn’t need it supplying power to anything at that point.
Hope that helps. Thank you for your question and good luck with your repair.
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