Changed monitor - blowing fuses

dkblue

Member
Joined
Apr 14, 2008
Messages
557
Reaction score
23
Location
Louisville, Kentucky
Alright, stick with me for a minute here. I had a weird sync problem with my Golden Tee monitor (25k7401). I couldn't figure out the problem but I lucked into another 25" monitor (25k7131) in a TMNT cabinet recently. I fired up TMNT and the monitor appeared to be working fine. So, I take it out, change the bracket, put it in my Golden Tee, hook up my power and immediately I get a blown fuse.

Now, the difference between the 2 machines is the power supply. In the TMNT there's an isolation transformer. Not so in the Golden Tee. However, it's a newer ps (much like one you'd find in a pc) and I thought isolation transformers weren't required?

Another thing, the old monitor had 3 pins presumably for line, ground, and neutral. But this monitor only has 2, what I think to be line and ground.

Anyone have any ideas? Is the solution as simple as use the isolation transformer? I would go ahead and try it, but I'm not sure how to put it into my circuit and I don't really want to spend hours trying to figure it out if someone here has a good idea that isn't the problem.

Thanks!
 
The 25k7131 requires an isolation transformer. Your power supply does not isolate the AC going to your monitor.
 
The 25K7131 definitely needs the isolation transformer. Your most likely blew some of your rectifying diodes, and maybe your voltage regulator, HOT, etc.

It's not hard to wire in an isolation transformer. You find the normal power to the monitor, (with it unplugged) cut those power wires, connect one side to the input of the isolation transformer, and connect the others side to the output.

Of course, you now have to fix the 7131 before you can use it again...
 
The 25K7131 definitely needs the isolation transformer. Your most likely blew some of your rectifying diodes, and maybe your voltage regulator, HOT, etc.

It's not hard to wire in an isolation transformer. You find the normal power to the monitor, (with it unplugged) cut those power wires, connect one side to the input of the isolation transformer, and connect the others side to the output.

Of course, you now have to fix the 7131 before you can use it again...

I see.... d'oh. Well, live and learn. Fortunately it wasn't a very expensive monitor if I did do some major damage. Oh well, I'll use it to fine tune my soldering skills.

On a side note, I wonder how many people I made smack their foreheads when they read this?

Thanks.
 
Sooo, one more question.... Since I hooked up the isolation transformer and I'm still blowing fuses, is that any indication of something more hosed now? I'm assuming along the lines of what was mentioned above that I likely blew?
 
Last edited:
yep its smoked. check the parts mentioned by mod.

Your gonna need at least a hot and voltage regulator, but theres most likely shorted diodes too... make sure you check those and check c36, it might be shorted

If you give up id buy the chassis and yoke off of ya depending on whatcha want for it..
 
yep its smoked. check the parts mentioned by mod.

Your gonna need at least a hot and voltage regulator, but theres most likely shorted diodes too... make sure you check those and check c36, it might be shorted

If you give up id buy the chassis and yoke off of ya depending on whatcha want for it..

Thanks for the help. Looks like I have a long saturday ahead of me. I'll attempt to fix it but if I get frustrated enough, I'll post back here or pm you. Now that I know my mistake, I might attempt to find a chassis some place. In that case, I'll let you know.

Thanks again guys.
 
I wouldnt give up just yet try changing the diodes in the bridge you should find 2 of the 4 shorted. you could replace them with origonals or 1n4007's should do you fine. After that if it still is dead then replace the chassis or send it to someone with a little more experience. Or this might me the perfect time to do some learning!!!
 
I wouldnt give up just yet try changing the diodes in the bridge you should find 2 of the 4 shorted. you could replace them with origonals or 1n4007's should do you fine. After that if it still is dead then replace the chassis or send it to someone with a little more experience. Or this might me the perfect time to do some learning!!!

Thanks for the info. But I'm still a newbie to the monitor world, only having installed a few cap kits. So I'm still learning my way around a schematic.

Would you check out the image linked and point me to the diodes you think might be shorted?

http://www.jstookey.com/arcade/WG_25k7191/k7191-complete_lg_.jpg

Thanks...
 
Your rectification diodes are D19-D22.

Thanks. I took a shot in the dark and thought those might be the ones to check. It looks like D20 and D21 are shorted. The other 2 read close to 500.

I also noticed I burned the ground trace on the edge nearest those diodes. That looks simple enough to repair. I guess I'll replace the 2 mentioned and see what happens.
 
Fixed!

Hey, thanks to everyone that helped. I replaced the 2 diodes mentioned, fixed my ground and it fired right up with a full, beautiful picture.

Thanks again and if you're ever in the central ky area, I'm buying the first round!
 
Back
Top Bottom