How are you measuring the coil resistance? Are you unsoldering it? Measuring it in the game you could be measuring parallel resistance from some other coil.

Now, if the coil has gotten toasted, many things could be a possibility. One of those is that some of the coil windings insulation has melted. A coil is made up of a continuous insulated copper wire, wound around a spool. The wire is coated with a clear vinyl to insulate it. If that insulation has gotten hot and melted you now have some places where the wire is touching itself as it winds around the spool. That effectively reduces the number of wraps or 'turns' you have in the coil, which will reduce its overall resistance, increase the current (which does increase the coil strength), and increase the heat to that coil. However, if it were causing the fuse to blow, it wouldn't be on power up, it would happen during game play. For the fuse to blow, you're getting a surge on power up.

During power up, do a bunch of coils fire or seem to twitch before the fuse blows? If so, I'd suspect your blanking circuit isn't working. The blanking circuit keeps the coils from firing during boot of the MPU. If not working and you're getting a bunch of simultaneous coils firing on power up, that could blow your fuse.

Caveat: I'm going by your testimony that F1 has anything to do with coil power...I haven't cracked a Sys11 manual to verify.

If this is another game you are flipping, you will have to replace the coil anyway - or no one will buy it.

If this is your own game, a coil can have seen high heat but still be good.

Check if the sleeve is tight. If it is, junk the coil.

Must be that Taxi for 200. That was a good quick find man....I emailed the seller after 13 minutes online and it was gone!

Like this coil looks toasted, but the sleeve moves freely, and it ohms out correctly:

burned coil.jpg

I left it in for the customer, but if the game was for sale, most customers would expect it to be replaced.

That's so awesome!

Really?!
26 posts in a hour...

http://pinside.com/pinball/forum/topic/replacing-batteries-with-a-memory-capacitor

http://pinside.com/pinball/forum/topic/mega-man-pinball

http://pinside.com/pinball/forum/topic/fs-nos-displays#postbox

http://pinside.com/pinball/forum/topic/big-game-stern-restore

Beats my record! Now THAT is so awesome!

From Clay's guide:

"When I turn my Fire! game on, the score displays would flash quickly at a high brightness, and the speakers would be noisy, but the game does nothing more."
Problem: the CPU board has a blanking circuit problem. The job of the blanking circuit is to shut down the score displays, solenoids and lamp circuits if there is a problem on the CPU. This safety circuit also protects other circuits during power-on if there is a problem.

Answer: there were two failed components, a 555 timer chip at U43 and a bad 2N4403 transistor at Q50.

To test the blanking circuit for proper operation, check U20 pin 2 or U43 pin 3 at power-on, using a logic probe. You should get an initial LO for a few seconds, followed by a continuous HI after the game has booted.

There's also some useful info in the Pinwiki on blanking circuit behavior: http://www.pinwiki.com/wiki/index.php?title=Williams_System_9_-_11

IIRC, the blanking circuit is one of the first areas to be affected by leaking batteries...Any battery damage to the MPU?

F1 has nothing to do with coils.

The fuse list is in that manual. I'd suggest that you take another look at it. F1 is mentioned more than once.

I wanted to post my thanks to robertmee for posting this. It directly helped me fix a Data East MPU that had these two exact same symptoms: Upon powering up the game, random display digits lit solid and all coils powered for about 1/10 of a second. After quickly power cycling the game, it booted normally and played perfect. The resolution was to replace the 555 timer that "blocks" the coils, displays, and such from energizing while the game first has power applied to it. Fixed it like a charm! THANK YOU!