Wells 25K7191 blowing line fuse??

[riddict]

I have a Wells Gardner 25" K7191 and every time I power on the cabinet, the line fuse blows. Shortly after the monitor chassis fuse will blow. The isolation transformer is one that was purchased on Twisted Quarter. Input 120V AC output 120V AC 120 Watts is the rating on the iso. Now I tried this in a couple different cabinets, both are Mortal Kombat cabs. One is an MK3 and one is an MK4. Neither one I believe has an iso, hence the reason I ordered the one from Twisted Quarter.

Could I be hooking up the iso wrong? From what I understand the AC main goes to the bottom two inputs, and the monitor power comes from the top two. Correct? And when wiring it up, does it matter which side HOT is on and which side is Neutral? For example the top and bottom prongs on the left side of the iso have the HOT connection (black) and the right side prongs have the neutral connection (white). But why is the cabinet fuse blowing?

 I should mention that both cabinets have their own monitors already in them, and both work 100% fine. It's not until I hook up the K7191 for testing that the fuses start blowing. The monitor powers up and you can hear HV enter the tube, but seconds later the line fuse blows. The chassis fuse itself blew one time as well after replacing a line fuse. Does this have anything to do with the iso? The flyback is new on the monitor as well as a new capkit and it worked as of six months ago. Please any help?

[MonMotha]

For grins, check that your iso transformer is actually isolating.  You should not be able to meter any continuity between an input terminal (either one) to an output terminal (either one).  If there's a connection there, the transformer has a short in it.  Never know when you'll get something DOA.

It doesn't matter which wire is hot/neutral on the iso.  In fact, it barely even matters which winding you use for the input and which one you use for the output, but the way you have it hooked up is normally what's the "correct" way.

You might also check that the fuse is fine if you power it up without the monitor attached at all, just the iso trans with no load.

If all that works, you've probably got a problem with the monitor.  Various faults will cause it to blow fuses.  Since you're getting HV, the horizontal section is probably fine, so check the vertical stuff.  The vertical output ICs like to fail shorted, which will blow the fuse.

[riddict]

Ok there is no continuity in the iso from bottom pins to top pins so the iso should be good then. I will next test to see if the fuse blows with just the iso and no load. If not, which it probably won't since the iso tests good, then I guess I will have to dive into this dang monitor chassis. That weird it blows the cabinet fuse if it is in fact the monitor.

[riddict]

Ok, on a side note, I have a Wei-Ya 825HR chassis that I ordered a little while back to keep around for a spare. Now if I decide to swap the K7191 chassis with the Wei-Ya, will it be fine? Yes the yoke measurements are 11 ohms vertical and about 1.5 ohms horizontal. Thats not the problem though. When I removed the neck board of the K7191 to examine the chassis, I noticed that it uses a 9 pin neck?? Is this normal for a K7191?

 I never had this monitor apart before, and purchased it from a local guy about six months ago. Of course he said it was working which is why I said it worked as of six months ago. Well upon further inspection I'm seeing things that just don't look right to me. I will take a few hi-res pics later today and post them so anyone can tell me whats going on here. I will explain what areas I'm refering to when I post the pics. But for now I just really need to know if the 9 pin neck will be compatible with the Wei-Ya Chassis.

[riddict]

Ok heres the pics. Notice a blue wire is cut going from the main board to the neck board? Whats the deal with that? I've done no repairs on this monitor, so none of this is my work. I also included a pic of some of the mods that apparently were done on the under side of the main board.

[SirPeale]

Ok heres the pics. Notice a blue wire is cut going from the main board to the neck board? Whats the deal with that? I've done no repairs on this monitor, so none of this is my work. I also included a pic of some of the mods that apparently were done on the under side of the main board.

That's one that I've recently run into.  It's apparently normal.  Leave it be.

If the cab fuse is blowing when you hook a monitor to it, but it's fine when it's not, the iso is fine.  Your monitor has some kind of short.  Or...you're using the wrong kind of cab fuse.  You're using a slo-blow fuse, right?

[riddict]

Yes I am using a 3A 250V Slow Blow fuse. That's odd that the one blue wire is cut. But yea I will leave it alone. Now to just try and figure out where the short is. Like I said it gets HV to the tube, so that area should be fine.

[riddict]

How do I test the vertical IC's? I understand there are four of them on this particular chassis? I assume this is where I should start looking since it was mentioned above. What other components should I look out for? Any other culprits in this case? Also if anyone could answer my question on the 9 pin neck on this monitor would be great. I just need to know if that will be a problem if I go ahead and use the wei-ya chassis instead.

[riddict]

heres another little tid bit I should mention. The last time I connected the monitor before posting my questions, the power supply made a pretty loud rumbling before the fuse blew. Thankfully I have a few power supplies laying around if it hurt anything. Now the power supply is a PC style Happ power pro. Obviously a plug n play supply for these MK cabinets. Once again when the games are on normally, everything is fine. In fact they still are. But it was only when I hooked up the K7191 for testing that things happen. Now why would the power supply rumble like that?

[riddict]

UPDATE: Ok, I went ahead and just put the wei-ya chassis on this monitor and everything is up and running fine. However there is a small pincushion issue that I can't get tweaked out with the pincushion pot. I got it to an acceptable level, but there is still a bit of an issue at the very edges of the screen that aren't too terribly noticeable. Obviously this must be caused by the yoke. So I guess at some point I will order the wei-ya yoke for this chassis and swap that out, but for now its up and running and working good. I plan to send the original wells gardner chassis to Chad at arcade cup in the future and have that repaired as well.