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What kind of fuse is this?

Discussion in 'Technical Discussion' started by Pascal, Mar 31, 2023.

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  1. Pascal

    Pascal Senior Member

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    Never seen one these till today… is it even a fuse? It s mounted side by side in a holder along with a conventional 6 amp fuse in the control box of our Alfa Laval filter.

    odd size : 6x27mm

    B50F2A02-9092-4D92-8E59-592CDCF6BA79.jpeg
  2. mapism

    mapism Senior Member

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    Glass tube fuses are rather common in Europe, though not so much in boats, but they are mostly 6x30mm, rather than 27.
    Besides, what is unusual in yours is that it looks like there's more than the usual filament inside it.
    Here's an example of the "usual" ones I am referring to: https://www.amazon.co.uk/gp/product/B07P97M2PY/
  3. Pascal

    Pascal Senior Member

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    That’s what I meant. What is inside doesn’t seem to be just the typical fuse. And it is 27mm long instead of the common 30mm or 5x20 of which I have plenty.

    they are inside the control the box for the Alfa Laval machine
    F670568A-E198-40A8-917C-124FA690B79B.jpeg
  4. Capt Ralph

    Capt Ralph Senior Member

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    Fuses can have mini springs and mini cooling coils in them along with the sacrificial filament.
    Fast blow, slow blow and other special effects are possible with these little fancy packages.
    I would guess you have a fuse, when blown, a lil led inside lights up
    OR, is lit when hot & good.
    It takes a micro scope sometimes, some numbers may be on it.

    The old main frames I used to work on had many of these lil surprises in them early 80s.
    Back then also, it was funny to find many fuses wrapped in cigarette wrapping foil.
  5. captholli

    captholli Senior Member

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    Looks to be a low voltage control medium lag or alarming fuse. Photos kind of fuzzy but that's my SWAG on this.
  6. Pascal

    Pascal Senior Member

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    Here is a better picture. I may indeed be used to trigger the alarm light and shut off both pumps.

    the king story is that while transferring and polishing fuel from the aft tank, the system shut down after about 400 gallons. Troubleshooting I realized the fuse to the feed pump had blown shutting down not only the feed pump but the Alfa Laval as well

    I replaced the 6 amp fuse but manage to loose the mystery fuse….

    the system works without it and I was able to transfer the remaining 600 gal but when the tank was empty only the feed pump shut down not the Alfa Laval.

    So you are probably right and this is used to trigger the alarm and shut down.

    Going to have to call Alfa Laval and get a couple of spare.

    as to the question “how can you be so stupid to loose a fuse”…. Well I guess we all have our moments :). Plus right after I took the picture, I had to go to the gate to receive two new air handlers… put the fuse in my pocket for safekeeping.

    Here is a better picture

    Attached Files:

  7. Paul S.

    Paul S. New Member

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    I don't think its a fuse, I think its a light bulb. Note the resister at the bottom. It could be a slow blow fuse, but leaning towards a light bulb.

    Is there any fuse rating info on it?
    f3504x4ps likes this.
  8. captholli

    captholli Senior Member

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    Better detail in this photo. Pretty confident that this is an alarming fuse. That would be a switching diode with what looks to be a neon tube that illuminates in alarm mode / no current mode. Resistors have a minimum of four-color stripes and never a single stripe.
  9. Pascal

    Pascal Senior Member

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    An alarming fuse to trigger an external light? As a light it serves no purpose as it is in a fuse holder, it self in a closed box which can not be opened if powered
  10. Paul S.

    Paul S. New Member

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    You can see the whole thing. Below could be 3 more bands. Yes, now that you mentioned it. It does look more like a neon light. They where common in the 60s and 70s
  11. captholli

    captholli Senior Member

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    Well, my scientific wild ass guess (SWAG) was way off. You sir are correct in the statement of a resistor being present. I had to break out the interwebs and look for this one and it turns out to be an indicator light fuse type or fuse type neon lamp that's primarily used in power supply circuits to visually show voltage present. Most of the fuse type holders shown had this small hole or window that the neon glow can be seen when looking at the circuit and components. I wasn't even in the ballpark SWAG wise... I couldn't download a clear photo but the exact item comes up under "indicator fuse type neon lamp " or "fuse type neon lamp"
  12. Capt Ralph

    Capt Ralph Senior Member

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    Along with a regular fuse. Special length and slot so a regular fuse won't fit. It may lite when the other fuse blows.
    The non filament lamp won't pass current (or much). That second pic did show a number stamped, any more numbers or mfg stamps?
  13. Pascal

    Pascal Senior Member

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    But a light would need both Hot and line… this twin holder only has one wire at the top, input and one at the bottom for output.
  14. captholli

    captholli Senior Member

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    Neon gas only needs voltage to ignite under vacuum. You can hold a bulb next or near to a high voltage transformer and it will ignite in your hand. in your application the gas will ignite with one line of voltage above 90 volts A.C. and I know that neon will burn with D.C. voltage also.
    RF will ignite the gas also as we used to hold a bulb next to the GTO 15 connection on a SSB antenna once in a while to test / make sure the radio had output and was transmitting.
    Capt Ralph likes this.
  15. Capt Ralph

    Capt Ralph Senior Member

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    I'm offering SWAGs also.
    Only your Hair-Dresser and the MFG know for sure.