New fuse for Astron 35?

Discussion in 'General Technical Questions and Answers' started by KM6LYW, Dec 21, 2018.

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  1. K8JD

    K8JD Ham Member QRZ Page

    Go to an automotive supply store! This fuse is readily available.
    W1TRY and KA0HCP like this.
  2. W0KDT

    W0KDT XML Subscriber QRZ Page

    The Astron parts lists shows "F1" as "FUSE, 8A SB" I just went through this for my Astron 35A and ended up with a 5-pack of Bussman MDL-8s $7.35 on eBay; I did not really price shop it.

    IIRC "3 AG" is an older mechanical (form factor) designation that served for both fast- and slow- blow fuses, then was replaced with AGC (fast blow) and MDL (slow blow) designators, which are the 3AG size.
    KB0MNM likes this.
  3. WA9SVD

    WA9SVD Ham Member QRZ Page

    MAY be readily available. Auto supply stores often use 32 Volt and 250 Volt fuses interchangeably, since the 250 Volt is usable at 32 Volts, but not vice versa. CHECK before you buy!
    N0TZU likes this.
  4. WA9SVD

    WA9SVD Ham Member QRZ Page

    When in doubt, use exactly what the manufacturer used; check the specs on the schematic. In this case, an 8 Amp, 250 Volt fuse is what was originally specified.
  5. W0KDT

    W0KDT XML Subscriber QRZ Page

    8 amp, 250v, SLOW BLOW
  6. WA9SVD

    WA9SVD Ham Member QRZ Page

    GOOD point. Many of us hadn't caught that earlier. Slow-blow fuses probably will NOT be available at auto stores, but places like F**'s should have them.
  7. W0KDT

    W0KDT XML Subscriber QRZ Page

    Yes. My Astron had a fast blow fuse when I bought it (used). Probably the OP's did too. That's why I chased down a box of the correct ones.
  8. KM6LYW

    KM6LYW Ham Member QRZ Page

    thanks guys, i know why the fuse blew, and it looks like a 250V fuse at 8amps will protect the supply (and my house from fire). i guess thats why fuses are rated in amps and not watts?
  9. K8MHZ

    K8MHZ Ham Member QRZ Page

    The voltage rating is how many volts the fuse can handle before it arcs over after it blows. If you notice, higher voltage fuses are physically larger because they need more room to stop an arc.

    The amperage rating is the protective rating of the fuse. It will protect at that amperage up to the voltage rating of the fuse.

    For instance, you already know the 8 amp fuse you have will interrupt a circuit adequately. Now, if that same circuit was 1000 volts and the fuse blew, current may still flow in the form of an arc around the blown element, not adequately protecting the circuit.
    N0TZU likes this.
  10. W0KDT

    W0KDT XML Subscriber QRZ Page

    Yup. (I-squared R) is what blows the fuse. V does not play there.

    & don't forget the slow-blow bit. The power-on inrush current in these big linear supplies is significant.

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