neo Mv u4 25" cabinet problems. monitor doesnt turn on

prosper1ne

King's Dry,
hey there, I've got one of the neo 25 inch mvu4 cabs. Lately the monitor hasn't been turning on when I turn the power on the cab. The marquee lights up fine and it looks like the monitor wants to turn on but it doesnt. Im not sure if its a connection problem? maybe the jamma harness connecting to the four slot motherboard is wearing? Maybe its the motherboard battery? Maybe its neither. Ive had the cab for like 10yrs and it used to work everytime. But now its always a struggle to get it going. I really dont know where to begin, but I want to fix it. any help would be greatly appreciated
 

xsq

Thou Shalt Not, Question Rot.,
Do you get sound?

The harness shouldn't be the source of your problem (or are you constantly switching out motherboards?). As to the battery: have you replaced it/done the coin cell mod? If not you should most definately inspect it and do so.
 

prosper1ne

King's Dry,
No I dont get sound. And im never switching out the mobo. Ive only recently been messing with the harness just troubleshooting. Ive never replaced the battery but when I checked it at a brief glance before I didnt see any corosion. Anything else I should check?
 

Kid Panda

The Chinese Kid
Do you get the buzzing sound that a CRT gives when turning on? If not, you may have a power supply problem if you're not getting sound as well. There may be enough juice to get the marquee light on, but not much more.
 

aclbandit

Another Striker
No I dont get sound. And im never switching out the mobo. Ive only recently been messing with the harness just troubleshooting. Ive never replaced the battery but when I checked it at a brief glance before I didnt see any corosion. Anything else I should check?

Hopefully this is a silly question, but do you have another board you can test with? Just make sure you've got an MVS-to-JAMMA adapter -- Neo has a slightly different pinout than standard JAMMA
 

prosper1ne

King's Dry,
Yea ive got some other boards. Ive got a 1 slot jamma board I can try. I guess I should get out a volt meter and test the psu too. Thanks for the help dudes
 

Nerdygrrl

Krauser's Shoe Shiner
A little clarification. Are you getting sound from the board/(s) AKA is it playing blind? Is there neckglow on the tube? When you say it sounds like it wants to come on what do you mean?

I may be wrong here as it has been a long time since I looked at the way the U4 is situated, but generally the monitor is run off the incoming AC and not the PS. Your monitor not turning on is something on the monitor chassis or with the monitor itself. Your marquee light is coming on so your AC input sounds like it is fine.

I had a problem with my U4 where the monitor would just cut out and not show a pic-the harness/molex on the chassis had a short/not making contact because of the way it is situated/folded over. It wore out over time
 

EllertMichael

Mickey's Coach
I had a problem with my U4 where the monitor would just cut out and not show a pic-the harness/molex on the chassis had a short/not making contact because of the way it is situated/folded over. It wore out over time

this actually turned out not to be the problem like we originally thought...

after replacing the wiring on the video harness, the monitor worked fine for a while but then went back to it's old blind antics again. :oh_no:

it turned out one of the small black pins that holds the vertical video board in place was missing, therefore the board wasn't making good contact with the pins. i put a small zip tie in the place of the missing pin and the monitor has been working 100%

pics of the board and pins/connector:
d08xbbJ.jpg

ZcUxnSQ.jpg

NeXis5e.jpg
 
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