wg 25k7191 blowing chassis fuses

[hawk007]

Hello everyone.  I have a neogeo mvs-4 with a 25k7191 monitor in it.  the monitor when it came to me never worked and was constantly blowing fuses.  I was told to recap and install a new hot and flyback which was done.  But when i went to fire up the game the monitor flashed and the game acted weird like random flashes and no sound etc.  So i unplugged the wires from the chassis to the jamma plug and turned it back on to have the monitor squeal and the game turn on but obviously no picture so i thought i would try again reconnected the wires and the same thing happened, weird acting and then the chassis fuse blew  and now it does the same thing as it did in the beginning again.  Constantly blowing chassis fuses and no signs of life.

The new flyback now has a little clear stuff coming out the top i would assume it is bad now?   Please help.    I also need to know how to attach the 5000v focus wire to the neck board.  Does it just pull apart or is there a trick?  Thanks soooo much.
Hawk

[grantspain]

a flyback would not just blow,
i would first make sure the monitor supply voltage is correct at 120vac and is running via an isolation transformer
next step if thats o.k is to disconnect the degauss coil from the chassis

also important that you have installed the caps,transistors and flyback correctly so that needs double checking
q11 and ic 4 will need to be checked

[hawk007]

It is the factory neo geo mvs power supply , and i see a transformer beside it.  { big coil looking thing}   


Before the fuse blew the last time the monitor would squeal like it wanted to work but was acting weird and the game would not start.  But now no signs of life again at all.  Did something go that i just replaced as it will not even squeal now?  I have the board out now so i will check the transistor work and the caps again to make sure i did everything right.

BTW where is the degauss coil?  what does it look like?  Sorry for so many silly questions but i am very new at monitor repair but i repair pinball games all the time.  Lots of board work but on pinballs only.  never video stuff.  But i must learn as it fascinates me.  Thanks so much for your Patience.

[grantspain]

after reading again i very much doubt there is any problem with the degauss circuit.
use the wells gardner site as it has a very good repair guide

why did you ask about the focus connection btw

[hawk007]

because i was going to solder the focus wires together as i did not think the focus wire came out of the neckboard.  But now i know not to but how do you get it in the neckboard ie open that plastic box or connection?

What happens if i soldered them together instead of opening that connection?  thanks for the point to the wells gardner site!  I will check it out right now. have a great day and thank  you so very much!

[grantspain]

depends on the crt socket type
most have a very small slot near where the wires goes in,you need to push a very small watchmakers screwdriver in the slot and then the wire just pulls out-when reintall you just simply push the wire in

if its a very old crt socket you may find that it has release flaps on the side and then the whole thing hinges up

some have a push in insert that holds the wire in place

if you got me a photo i could say which you have

[Ken Layton]

The flyback for this model has two wires coming out of it. The smaller gauge wire is the "SCREEN" voltage and goes to that single pin push on terminal on the neck board. The larger gauge wire is the "FOCUS" voltage wire (8000 volts!!!!!!) and connects inside the picture tube socket on the neckboard. There are two types of picture tube sockets that Welss-Gardner used on their neckboards. On one type (less common), there is a little flip latch that you release. This allows the wire to simply slide straight out (pressure fit). Then you push the new wire in and flip the latch back down (no soldering needed on this style).

The other style you may have to unsolder the whole picture tube socket from the neckboard. Then you'll see to release tabs on the side of the socket. Releasing BOTH tabs allows the plastic cover to slide backwards revealing a solder terminal where the focus wire is soldered to.

[SirPeale]

See?  I told you you'd get a lot of help here.

[hawk007]

Thank you king Arthur for pointing me in this direction.  You are the man!

And thank you to the help from everyone!  Your time and expertise is greatly appreciated!  May the sun always shine on you guys eh.  Many thanks again and i will post after i checked the stuff i was told to check.     Evergratefull
Hawk

p.s. i will try and post a pic of the neckboard asap

[hawk007]

O.k.  the board is out again.  I have gone over everything and it all looks o.k.  My focus wire is the less common type that lifts the flap pull out and replace and drop flap again.  So that is done.  But how do i know this flyback is anygood anymore as the monitor stopped squealing and blew fuses right away again like before .  I replaced everything and it fired  a couple of times but now the same thing as before i replaced the parts.   

Also how do i test the diodes in?  I did that but they read almost the same both ways.  And how should i test the hot and ic4 and q 11.  Thanks again for all the help.

i might have to send someone my board to fix then i will reinstall as this seems to be more than the recapp i thought it would be. DOH   This is all new ground and a little intimidating to say the least.

[grantspain]

i think you may be wise to send this for a repair,you need to know how to use a multimeter and read a schematic to fix this
diodes need one side to removed from the board to read correctly,to some extent the same with transistors

[hawk007]

I am very good with a multi meter but i have not worked on such things before and to prevent too much replacing of parts that i have killed or simply to ease the repair and stress level, i think i will take your advice and seek help.  hehe.

Would any tv repair shop be able to fix this?  Thanks so much

[SirPeale]

Send it to Chad @ ArcadeCup.

[grantspain]

take that to a tv shop and watch the fella go "ohhh,nah mate-don't have a clue on this",
ken and peale should know some repair peeps

[hawk007]

So they want 120 plus shipping to repair my chassis.  I think i might have another stab at it as i already bought parts .  Does the flyback always go up with a bang or can they go silently?  Also do you think my hot is now blown as well cause it will not even fire again at all. just blows fuses .
Also i was told to replace the voltage reg and hot again and a field coil?  as well and that should fix it.  Any suggestions?