Neo Geo 4 slot monitor not working

AUSyTyIN

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I've never had to diagnose a monitor issue before, so I'm not sure where to start. I can hear the monitor fire up, but it never displays anything. So, what's the diagnosis procedure?
 
I just noticed the marquee isn't lighting up either. I've never ran into a marquee that is like this one, so I'm not sure if it could be a related problem? When the power on, it looks like this:

IMAG0060.jpg
 
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It's a Wells K7000 series.

Yep, WG 25k7193 to be exact (it's on that white sticker).

The marquee light in the 4 slots like that is what's called EL lights. They are run by the Neo motherboard and whichever game is currently selected on the screen, it's marquee "square" is lit up while the other 3 aren't. These almost always are non-functional or only partially working. The most cost efective solution to these is to take out the EL lighting and wire up a normal marquee light. And this should have nothing to do with your monitor issue.
 
Start by checking the B+ voltage. Then we'll go from there.

I get 380V on both sides of the voltage regulator with my better multimeter, but 0V on my crappy Harbor Freight one (I wanted to double check that reading). Is 380 even possible?
 
Alright, I just had an "I'm an idiot" moment. I was checking the voltage in AC, not DC. The voltage is 172V on both sides of the voltage regulator, so I'm thinking my problem isn't in the board (at least on the Neo Geo monitor). Is it a bad power supply, or is there something else wrong?
 
Ok. Let's start over. You have no pic. I'm guessing the fuse is not blown. Next you need to test the B+ on R301. The large white white rectangular resistor on the outside edge of the metal cage. Red probe to one of the leads and the black probe to ground. You should have about 130 volts. The voltage regulator is the IC at IC4 on the inside of the metal cage. Did you test at the resistor or the VR? My guess is the resistor. If you did, 172v is too high. Let me know and we'll move to the next step.
 
Ok. Let's start over. You have no pic. I'm guessing the fuse is not blown. Next you need to test the B+ on R301. The large white white rectangular resistor on the outside edge of the metal cage. Red probe to one of the leads and the black probe to ground. You should have about 130 volts. The voltage regulator is the IC at IC4 on the inside of the metal cage. Did you test at the resistor or the VR? My guess is the resistor. If you did, 172v is too high. Let me know and we'll move to the next step.

The fuse is not blown. I checked checked the voltage at the large white box at the top left of this pic (the red wire partiall covers it). Is that not the correct spot to measure B+? I found a pic on this site saying that was where to check it, but from what you are saying, that is just a resistor, not the VR?
IMAG0068.jpg
 
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Yes. That is where you test it. That isn't the VR though. The VR is the ic at location IC4. That resistor is the next stop for the voltage after the VR. That's why we test it there. No pic with these voltages suggests that your chassis is in HV shutdown.

The voltage you got is too high so this would indicate a bad VR or a bad cap c57. The cap is included in a cap kit so if you do a cap kit that will rule out the cap.

Anyways, the confirm that the VR is the problem there is a diode you can unsolder. If you get a pic then we will know that the VR or cap is the problem for sure. I don't have my schematics with me here at work so I'll tell you which one to unsolder after work.

In the meantime go over your chassis and look for bad solder and reflow all of the solder on your header pins regardless of if they look "ok". It'll only take a few minutes.

Edit: changed to correct cap.
 
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Sorry, but what is a header pin? Like I said, I'm stupid new to monitors, and circuit boards in general (the last one I touched was 15 years ago in 7th grade).

And I did check the solders, and they all look good to my untrained eye...
 
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