This is from RGP - Mark Clayton - I've done it on EMs FWIW
...

Take one of your blown fuses, and using some short wires
solder a 44 or 47 light bulb across it. Now install
it in the place where your fuse is blowing. All the
lights will be dim, but when the short happens again,
the bulb across the fuse will light up fully. Now you
can wiggle things and fiddle around until you find the
short, and you won't blow any more fuses.
-Mark
-----
http://pinballpal.com

Forgot to mention, after installing the bulb - un-solder sections of the GI string until the short disappears.

Check continuity between Gi lights with a multimeter. Power off obviously.

Ahh just had this problem on a Space Shuttle. One of the most frustrating times. First you have to determine the short. Test continuity from back box to GI. If all of that is good, check your bulbs. It is possible to get a bad bulb that causes a short (unlikely but possible). Next look for any wires touching underneath the playfield (this is the most likely scenario). Especially pay attention to the staples that hold in GI. It is possible that it is touching the socket body. Make sure to also check for metal shavings or solder that could have made their way to the sockets. Last case scenario and what was wrong with mine was a bad light socket. I sectioned off certain section of GI into smaller sections by disconnecting from game and unsoldering sections. I then checked the Ohms with a multimeter in the lowest setting. Test the light sockets themselves on the tabs on the bottom, this will check the entire section. If that section was good, it would read NL. If there was a short in that section, it would read a number (0.01 to whatever). Then you had to unsolder each socket in the bad section until you found the light socket that was bad. It worked for me just a lot of soldering and unsoldering.

Funny, I have a DD and while trying to fix the issue with my ball save issue, I have no blown fuses, but NONE of my playfield lights that illuminate the field work....all the ones in the PF work fine....strange, but true...

Hahahaha, but WE have the BEST machine for the money available out there, IMHO....everyone that plays it loves it !!

Excellent commentary, Jared!!!
Mike

Most GI bulbs should measure between 3 ohm and 5 ohm resistance. If the string is shorted, it will usually read 1 or 2 ohm... If it's 1, the fuse will blow very quickly. If 2ish, it will sometimes take a few seconds to blow and the lights will be VERY bright for those few seconds.

I had this happen on my Harlem and Bow and Arrow. In both cases, it was a bad "shorted closed" bulb. In order to determine this, I removed every bulb in the string and just replaced them with new. Neither have ever shorted again. Your mileage may vary but if it's easy to pull all the bulbs, (you can sometimes remove GI from under the playfield much quicker) it may be worth trying to see if the short is still there. You may also have to desolder the GI wires at the source of the string.

You mileage may vary but hopefully something here helps clarify things.

I have also had a shorted bulb right out of a brand new package. It does happen!

Follow what Snyper said then. Do yourself a favor and get aerosol keyboard cleaner and spray the sockets while you are pulling out the bulbs. It is possible you knocked something in while changing bulbs.

Bump to save this very helpful thread.

Brilliant...
Thanks Mr Clayton

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Hello,
This is some great information !! My Playfield GI is dead shorted and blowing a fuse as soon as you put one in on my Gottlieb Fast Draw !! It has been driving me nuts !! Now to start the trouble shooting !! Thank you !!!!

Use a 9v battery, hook alligator clips to it, then with the game off touch the clips to a socket. See which bulb in the string doesn't light and youve found your problem.