25K7193 blowing fuses...at the iso

Bullwinkle

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I have a chance to pick up a Sega Spiderman. The monitor inside is a WG 25K7193. I checked it out and there was no power going to the monitor. There is a fuse down by the iso, which, when replaced, blows immediately when powered up. I then disconnected the monitor from the power connector, replaced the fuse again and the machine powers up and plays blind, but as soon as I plug in the monitor...it pops the fuse.

Any suggestions on what to look for to see what might be shorting this out? I've dealt with blown fuses on the chassis before, but never had a monitor cause the fuse next to the iso to blow.

thanks,

tom
 
Couple things - are you using the correct size fuses? Also, they should be slow blow (the degauss circuit draws a quick burst of current).

Check the resistance between the two AC input wires of the monitor - see if there is a direct short there. I take it that the fuses on the chassis aren't blown?

Try disconnecting the degauss coil. Sometimes a shorted thermistor can cause the fuse to blow.

How does the flyback look? Any cracks? Does it have white knobs or black ones?

If everything looks good, you'll have to work your way through the circuit, checking for shorted components. Look at the schematic and follow your way up from the power input. Check the rectifier diodes and the voltage regulator especially.

-Ian
 
All of that is good information but also check the four input diodes. They form a bridge rectifier and if one is shorted it will blow the cab fuse but not necessarily the chassis fuse.
 
Thanks guys...I will check all items mentioned when I get over there... I do know that the chassis fuses are not blown...I also know that the fuse by the ISO is a 1amp fast blo and there is a sticker on the fuse block with that value and type printed on it... I can certainly try a sloblo but will try disconnecting the degaus coil first.

Thanks again... At least I have a place to start now... Much appreciated.
 
The manual calls for a slo blo.

Wow... I will take a snapshot of this... The label definitely does not! Wondering if this is not original or (more likely) a mis labelled fuse or..maybe someone labelled it and the sticker is not a mfgr sticker. In any case...I will load it up with a sloblo 1amp and see if that solves it before I do anything else.

Thanks for the headsup
 
I have a spiderman cab, the only fuse on my machine is accessable from the outside of the machine where the lower power switch and the AC Power Cord socket in. it's a 5amp fuse and also says it on the metal plate that everything goes into (power cord, switch, fuse).

I don't believe it's a slow blow fuse (in my machine) as i don't remember ever replacing it and if i had i'm positive that i didn't replace it with a slo-blow.

I would think that there's a short somewhere (maybe in the ac power line that goes to the monitor located by the flyback). or that the 1amp fuse just isn't enough :D
 

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@ Broodwich - Is your cabinet a conversion ?
 

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it was converted to Alien Vs. Predator but was originally Spider-Man


edit: sorry i guess i'm no help as my machine is definitely not original when it comes to the power supply and fuse. in the first pic you can see the 1A 125v Fuse Caution label stuck to the iso block. thanks kevinmullins i never noticed that.
 
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it was converted to Alien Vs. Predator but was originally Spider-Man


edit: sorry i guess i'm no help as my machine is definitely not original when it comes to the power supply and fuse. in the first pic you can see the 1A 125v Fuse Caution label stuck to the iso block. thanks kevinmullins i never noticed that.

That's the exact same label I have...1a 125v but there is a fuse right above it on the one I'm looking at. I'm pretty sure it doesn't say slowblo either.
 
the sticker definitely doesn't say slo-blow but the manual does i'd go with the manual since it's being more specific.

if the fuse doesn't make any difference i'd think there's a short somewhere. that's the only advice i can give you as i've replaced my iso and the rest isn't original power supply and wiring wise :( (you can see both my nba jam soundboard pots in that pic too lol as this is my multi jamma cab).
 
That's the exact same label I have...1a 125v but there is a fuse right above it on the one I'm looking at. I'm pretty sure it doesn't say slowblo either.

"Most" of the time they won't say SB or FB, some of the older games might, but the newer ones tend to leave you getting out the manual to check.
Typically a monitor will have a slow blow fuse on the line voltage because of the current surge mentioned earlier.

Grab some pics of your setup if you can.

I just hate to get too far into troubleshooting the monitor itself until we clarify this fuse thing.
 
i agree w/ Kevin, pictures always tell the full story.

I'll take a pic of it when I get there and post it on here, but it really is exactly the same as your first pic, except there is a fuse just above the label for the 1A 125v Fuse.

If I can identify the issue or feel comfortable that I'll be able to remedy the problem, i'll grab the game.
 
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