(Topic ID: 78857)

tech: Slow Blow vs. MDL fuses


By mof

5 years ago



Topic Stats

  • 27 posts
  • 15 Pinsiders participating
  • Latest reply 1 year ago by G-P-E
  • Topic is favorited by 12 Pinsiders

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    #1 5 years ago

    1. What is the difference between a SB and an MDL fuse?
    2. Is the difference important enough to pay attention to for pinball? (If so, when is that the case?)

    thanks!
    -mof

    #2 5 years ago

    MDL is slo blow to my knowledge.

    You want the difference between MDL (slo blow) and AGC (fast blow). Slow blow simply means it takes more time at a given current level for the fuse to break.

    In pinball, the current to coils is very 'spikey' and this can blow fast blow fuses, even though the amount of power being driven isn't enough to damage components, so a lot of fuses in a pinball machine are slo blow for this reason.

    As a general rule of thumb, a fast blow fuse can be safely used anywhere a slow blow can however it can blow in service too easily.

    A slow blow should NEVER be used where a fast blow is specified.

    #3 5 years ago

    Another slow blow name is MSL, this was the older terminology.

    Something else to keep in mind is usually slow blow IS SPECIFIED on a fuse chart when a slow blow is called for. It will say "7A S.B." for instance. Fast blow isn't always specified directly, it's assumed. So if a fuse chart says "7A S.B" and then has "3A" listed for another fuse, it's calling for a 7A slow blow and a 3A fast blow.

    #4 5 years ago

    Sounds like there are two physical differences between Slow Blow and MDL fuses:

    * A Slow Blow has a spring at one end. The spring terminates into a wire that runs to the other side of the fuse.

    * An MDL (Method Detection Limit) is a coil of wire wrapped around a wire core.

    Can we use either one in pinball when slow blow is required?

    thanks,
    -mof

    #5 5 years ago

    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

    #6 5 years ago

    Also, I sometimes see:
    "312" for AGC
    "313" for MDL
    -mof

    #7 5 years ago
    Quoted from mof:

    Also,
    "312" for AGC
    "313" for MDL
    -mof

    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

    #8 5 years ago

    One thing I have not seen in this thread is the NB or Normal Blow fuse.
    Every WPC pin around "F114" calls for a 8A 32V NB fuse.
    These fuses have a thin flat wire in them from the factory. I have yet to find one of these either at Radio Shack or an automotive store.

    -1
    #9 5 years ago
    Quoted from Arcade:

    One thing I have not seen in this thread is the NB or Normal Blow fuse.
    Every WPC pin around "F114" calls for a 8A 32V NB fuse.
    These fuses have a thin flat wire in them from the factory. I have yet to find one of these either at Radio Shack or an automotive store.

    Try here
    http://www.mouser.com/Circuit-Protection/Fuses/_/N-ba85y?P=1yya41c&gclid=CO6A5uTEpLwCFUYOOgoddgsA1g

    #11 5 years ago
    Quoted from Arcade:

    One thing I have not seen in this thread is the NB or Normal Blow fuse.
    Every WPC pin around "F114" calls for a 8A 32V NB fuse.
    These fuses have a thin flat wire in them from the factory. I have yet to find one of these either at Radio Shack or an automotive store.

    That would be a standard Busmann AGC-8 or Littelfuse 312008.

    #12 5 years ago
    Quoted from G-P-E:

    That would be a standard Busmann AGC-8 or Littelfuse 312008.

    The 312008 is obsolete and NLA and was just a FB fuse without the flat blade inside.
    The Busmann AGC-8 looks to be just a standard FB fuse you can get anywhere.
    I'm just wondering why every machine I have seen, comes with those flat blade fuses in that slot and not anywhere else on the board.
    On the Williams Fuse chart is calls for all FB and SB fuses except for one spot. It always has a specific 8A 32V NB fuse called for in that spot.
    I'm sure that just putting a regular fuse in that spot is fine, just wondering why it is specifically different.

    #13 5 years ago

    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

    #14 5 years ago

    You can always use a fuse rated for a higher voltage, just not lower. In other words, you don't want to use a fuse rated at 32V in a 120 or 240V circuit due to the possibility of arcing across the blown fuse.

    I bet Viper is correct in that 8 amp 120V fuses were not common at the time and didn't want to cause confusing by specifying a higher voltage or not specifying it at all.

    #15 5 years ago
    Quoted from Arcade:

    The 312008 is obsolete and NLA and was just a FB fuse without the flat blade inside.
    The Busmann AGC-8 looks to be just a standard FB fuse you can get anywhere.
    I'm just wondering why every machine I have seen, comes with those flat blade fuses in that slot and not anywhere else on the board.
    On the Williams Fuse chart is calls for all FB and SB fuses except for one spot. It always has a specific 8A 32V NB fuse called for in that spot.
    I'm sure that just putting a regular fuse in that spot is fine, just wondering why it is specifically different.

    312008's are still made -- I buy boxes of 312 series fuses pretty much every month. Need complete part number to get to current ones such as 312008.HXP for fast glass, 8 amp, RoHS compliant (XP suffix), box of 100 (H in suffix). Or 312008.MXP for box of 1000. But when sold as individuals, the "H" and "M" are dropped. Also, for reason only Littelfuse knows, they also added a zero ahead of the part number so that it would be 0312008 but most people ignore the preceeding zero.

    Not sure what you mean by blade fuse. All I can think of is automotive blade fuse - ugly plastic buggers. 312008's and MDL-8's are 100% identical other than different manufacturer.

    FB and NB are used synonymously in this line of work. As far as we're concerned - FB = NB.

    The high current fuses normally have a lower voltage rating. Few years ago, used to be 10 amps and above were rated 32V.... now I think 12A and above are rated at only 32V and everything less is 250V (MDL and 312s). Although it predates me, I wouldn't doubt it if the 8 amp fuses were only rated up to 8 amps in the not too distant past. Always ok to go higher in voltage rating.

    #16 5 years ago
    Quoted from G-P-E:

    Not sure what you mean by blade fuse. All I can think of is automotive blade fuse - ugly plastic buggers.

    When I say blade fuse, I am not talking about the little plastic U shaped push in fuses for cars.
    However the metal end of one of those fuses is a great example of what is inside the NB fuses that Williams used.
    It is a normal looking glass fuse but it has a "metal blade" inside it, not a wire like regular fuses have.

    #17 5 years ago
    Quoted from Arcade:

    When I say blade fuse, I am not talking about the little plastic U shaped push in fuses for cars.
    However the metal end of one of those fuses is a great example of what is inside the NB fuses that Williams used.
    It is a normal looking glass fuse but it has a "metal blade" inside it, not a wire like regular fuses have.

    Actually I believe what you are seeing that you call bladed is just the higher am fuses. Some manufacturer use 'flat' filaments instead of 'round' drawn out wire. And on the flat ones they tend to change the width of the 'waist' to change to rating.

    1 month later
    #18 5 years ago

    I'm troubleshooting a JM hand issue and just pulled my fuses. Found some discrepancies, then found this thread. In the power driver board F114 spot was an 8A MDL fuse. The manual calls for 8A N.B. From reading this thread, I'm assuming I need to replace this one with a 8A F.B.?

    #19 5 years ago

    Yes.

    Not an 8A SB

    2 years later
    #20 2 years ago

    Dredging up an old thread here.....

    I'm sorting thru my stash of fuses this morning and there are several 1 1/4" ones whose stampings I can't fully decode, here are a couple of examples:

    F8A250
    F20AL250V

    Obviously these are 8A and 20A at 250V, but what does the "F" stand for? And why "20AL" instead of just "20A"? There are no other stampings on them.

    Happy New Year everyone!

    #21 2 years ago

    F = "fuse" AKAIK.

    #22 2 years ago

    F8A250
    F = Fast
    8A = 8 Amp
    250 = 250V

    I don't know what the "L" stands for. Are there any manufacturer symbols on it?

    #23 2 years ago

    Articles to read for complete education and experience regarding all aspects and types of fuses for pinball machines:

    https://web.archive.org/web/20070811193546/http://www.circuitprotection.ca/fuseology.html

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

    #24 2 years ago
    Quoted from G-P-E:

    F8A250
    F = Fast
    8A = 8 Amp
    250 = 250V
    I don't know what the "L" stands for. Are there any manufacturer symbols on it?

    Nope, nothing else at all. I figured F might be fast but I have yet to see an S (or whatever letter) to denote slow or time-delay.

    #25 2 years ago

    I've just been schooled

    #26 2 years ago

    Also euro/china makers use "T" (timed) as their slow blow designation.

    6 months later
    #27 1 year ago
    Quoted from G-P-E:

    312008's are still made -- I buy boxes of 312 series fuses pretty much every month. Need complete part number to get to current ones such as 312008.HXP for fast glass, 8 amp, RoHS compliant (XP suffix), box of 100 (H in suffix). Or 312008.MXP for box of 1000. But when sold as individuals, the "H" and "M" are dropped. Also, for reason only Littelfuse knows, they also added a zero ahead of the part number so that it would be 0312008 but most people ignore the preceeding zero.
    Not sure what you mean by blade fuse. All I can think of is automotive blade fuse - ugly plastic buggers. 312008's and MDL-8's are 100% identical other than different manufacturer.
    FB and NB are used synonymously in this line of work. As far as we're concerned - FB = NB.
    The high current fuses normally have a lower voltage rating. Few years ago, used to be 10 amps and above were rated 32V.... now I think 12A and above are rated at only 32V and everything less is 250V (MDL and 312s). Although it predates me, I wouldn't doubt it if the 8 amp fuses were only rated up to 8 amps in the not too distant past. Always ok to go higher in voltage rating.

    ... and nobody caught my blatant typos in this one.
    "313008" is the slow blow version which is alternate to Bussmann MDL fuses.
    "312008" is the fast (normal blow) version which is alternate to Bussmann AGC fuses.

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