I'm working on a problem with my MB where F107 blows within the first 1-2 games after replacing the fuse. I think I've narrowed it down to the problem being somewhere in the backbox (fuse doesn't blow with backbox lights disconnected). Maybe another post on help fixing that later  

However I only have fast blow fuses right now, and F107 should be slow blow. My question is assuming same amp and voltage rating will it damage anything to use a fast blow in place of a slow blow in F107 so the playfield flashers work until I get new fuses (and eventually fix the backbox) ?

I'm not an engineer but i would assume a fast-blow can be used instead of a slow-blow with no problems other than it may do just that, blow faster if a current overload happen.

Fast-blow is more sensitive and will blow faster to protect sensitive circuits from overload. So in any cases, you're more protected with a fast-blow than a slow-blow but the circuit might be designed in a way that it overloads from time to time but not enough to blow the slow-blow fuse but will blow the other... ah well, try one and see if it holds up, it wont break your game

Here's a good article to prove my point: http://www.contentmart.com/articles/30445/1/What-is-a-Fuse--And-how-to-test-it/Page1.html

"Do not use a slow blow fuse in place of a fast acting fuse. It may not open fast enough to prevent components damage under a high current condition. It's not harmful to replace a slow blow fuse with a fast-acting fuse, but it will probably open up unnecessarily every now and then when the equipment is first switch on."

You can use the fast blow without doing any damange as long as the rating is the same as the slow blow. But even if there isn't a problem with that part of the curcuit, the in-rush current might be enough to blow the fast-blow fuse.  (hence the need for a slow-blow)

D

Thanks guys...That's what I was thinking

Fuses are the same rating!

Watch for my next post on help with troubleshooting the flasher circuit in the backbox!