Everything you ever wanted to know about fuses.

http://www.flippers.com/fuses.html

One thing John doesn't discuss is what "MDL" stands for.

"AGC" stands for "automotive glass cartridge"
"MDL" stands for "method detection limit"

It is generally understood that an "AGC" fuse is fast blow whereas a "MDL" fuse is slow blow.

viperrwk

312 and 313 are specifically for Littelfuse.

In the glass cartridge variety for the 1/4 x 1 1/4" size, "time delay" fuses are
New Edison - MDL
Old Edison - BDL
Bussmann - MDL
Old Bussmann - MSL (http://tinyurl.com/mgjbq2c)
Gould - GDL
Littelfuse - 313

For "fast acting"
New Edison - AGC
Old Edison - BGC
Bussmann - AGC
Gould - GGC
Littelfuse - 312

So a fuse that has on it 3A BDL is a 3A slow blow fuse made by the old Edison company.

viperrwk

If you look at the manuals for the fuse charts in WPC games, Funhouse (WPC A/N) specified "8A NB" at F114, and SB everywhere else. Party Zone (WPC DM) did the same but interestingly specified an 8A NB for domestic game line filter and 4A SB for a foreign game. This is the same for TAF (WPC Fliptronics 1.) TZ (Fliptronics 2) is also the same except the line filter where it only says "8A" for domestic and "5A SB" for foreign.

It isn't until you get specifically to JD (DCS, Aug 1993) where Williams specified "8A 32V NB" at F114. They also changed fuse types in other places with this game. Specifically on the DMD controller and F115 they went from SB to FB fuses while keeping the fuse ratings the same. This only continued until the last DCS game, Popeye. Then when Williams switched to WPC-95 they went to all 5x20mm time delay (slow blow) fuses with everything being rated at 250V.

If you look at this old Bussmann catalog that John Robertson posted - http://www.flippers.com/pdfs/Buss_Fuses_Catalog_569.pdf - you will notice that not all fuse values come in all types. It also distinguishes between "fast acting" and a "glass tube" fuse in the 1/4" x 1 1/4" size where the fast acting will open at 200% load in 5 seconds or less. I would say this is one of the defining features of a fast acting fuse.

And since not all fuse values came in all types and sizes, Williams fuse selection reflected that. I would guess to eliminate confusion they specified 8A, 32V NB fuses starting with JD because that's what ops had stocks of on hand and perhaps at the time you started seeing higher voltage rated fuses in the FB variety. If someone knows the history and timeline of glass cartridge fuses please chime in!

So then you might ask why didn't Williams update the docs to allow for a range of choices? Good question. I would say that to do so would create more confusion with people asking questions rather than simply laying down the law in the manual. But this is speculation on my part.

viperrwk