25"CGA Makvision by Wei-Ya Monitor questions

[ScottyDutch]

I am pretty new to repairing Arcade machines, but am loving the hobby so far.  I have done some soldering and electronics work, but am still learning about monitors.  I have a 25" CGA Makvision by Wei-Ya in a Daytona USA cabinet.  The arcade powers on, multiple lights, I can hear things when I press buttons, but there is no power to the monitor.  I have tested voltage off the power supply and up to the monitor.  I know I may get to the point where I have to pull the monitor.  While looking at the board I saw the attached.  There is a 3 wire (white, green, black) plug going into the board.  The issue I see is that the black line (which I tested and is hot) is going into the AC-N (neutral?) input, while the white neutral is going into the AC-L (line?).  Is there a possibility that these wires got reversed somewhere along the way? Thank you for your help.     

[lilshawn]

well, live and neutral ARE switched around, but for the most part... it's not really a big deal. if you are so inclined, unpin the connector and fix it, otherwise just reverse the wires to just make sure to maintain live and neutral down the line. makes things safer overall.

as for being dead... check your fuse next to the power connector and see if it's broken. if not, power up the monitor just by itself (unplug the power from everything else in the cabinet so it's silent) and see if you can hear a faint "tic tic tic" or buzzing coming from the monitor when it's power up (that also slows down when the power is removed). if this is the case, it's got a short somewhere that needs to be found (likely a HOT or capacitor)

otherwise, you are going to be getting into checking power rails and whatnot.

[ScottyDutch]

Thank you, I appreciate it.  I will check that fuse, but I'm almost positive it was good.  I will do the test you recommended tonight, but I'm thinking its probably a capacitor.  Thank you.

[lilshawn]

yeah, from your picture it still looks good. it's not OBVIOUSLY blown as they usually sputter black stuff all inside... but the filament inside could still be broken and just flapping around in there from vibrations or being knocked... it's not unheard of. double check with a voltmeter to be extra sure.

[ScottyDutch]

Checked the fuse last night and it was good, unfortunately there goes the easy fix!  When I power up the monitor I can hear a buzzing and the "click click" noise which leads me to believe a short.  So the next step would be to do a re-cap? 

[lilshawn]

tick tick tick, is an indication that the B+ is overloaded and the SMPS power supply is gone into protect mode. when it does this, it continuously tries to restart in case it was just a fluke from having to recharge filter capacitors.

probably wouldn't hurt to do a re-cap, they look like they might be original, in which case they are 20 some years old. but you might be looking at a HOT for it as well.

if you post what the actual monitor chassis number is (probably like a CH-666 or 2525 or something like that) i can see how the HOT is in circuit and tell you the best way to test it to see if it's still good or obviously blown out.

[ScottyDutch]

Thank you, I appreciate all your help with this. I didn't see a CH number, but I attached a couple of photos of the back of the monitor. If you think it might be somewhere else, please just let me know.

[lilshawn]

M3125

it's a makvision branded 95% clone of the CH666 chassis with a modified neckboard and a handful of different parts.

6 out of 10 times it's caps. the other 3 times a dead HOT (sometimes both)... and one, the stupid resolution detection IC.

check the HOT (powered off) by measuring resistance across the middle and right most legs (the collector and emitter) should read something OTHER than shorted together. not a definitive test, but rules out an obvious issue there. if it measures in 100's or 1000's of ohms, go ahead and replace all the low voltage electrolytic caps 100uf and higher and all the high voltage electrolytic caps. (or buy a kit)

that will probably get you going again.

if it's still doing it, replace the HOT. sometimes they test okay, buy fail under high voltage stress. it'll be a 2S5302 buy from a reputable distributor, not ebay.

if still not, could be one of the big high voltage orange/brown/blue polymer plastic dipped caps is shorted out. common failure mode is shorted so run around and test with your meter looking for one's legs connected when it shouldn't be. they should all read some resistance...not 0.

[ScottyDutch]

Thank you, it looks like I have some work to do!

[grantspain]

flybacks are failing on these in a big way now