New fuse for Astron 35?

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

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  1. KA9JLM

    KA9JLM Ham Member QRZ Page

    These glowing fuses may be counterfeit.

    A fuse should blow, It should not glow.
  2. W9WQA

    W9WQA Ham Member QRZ Page

    if you read this post you would see that i just stuck them in to test the power block,not to use.
    found them!, .5 amp and 5 amp,250 volt.
    i guess i stuck them to do a check out and never used them, until the radio test.
    they measure1.4 and .7 ohm.
    they will glow with a short on 12 v."
    never used them, until the radio test."

    a .5 amp line volt fuse is actually a small wirewound resistor. mine measured 1.4 ohms or a little less. i found more in my 'warehouse" barn and will try to dupe that 2 metr radio test done origionally.
    im not making stuff up, just reporting what happened...

    just took "glow pix, how to post?
    Last edited: Jun 18, 2019
  3. KA9JLM

    KA9JLM Ham Member QRZ Page

    Right click on picture and select Copy.

    Then right click in your reply here and click Paste.

    Are your meter leads zeroed ?
    Last edited: Jun 18, 2019
  4. W9WQA

    W9WQA Ham Member QRZ Page

    mine measured 1.4 ohms or a little less.
    this is about 1 amp, not the way i did b4. just a variable supply upload_2019-6-18_11-45-26.jpeg
  5. KC8VWM

    KC8VWM Ham Member QRZ Page

    Isn't that the darndest thing you ever seen?
  6. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    I once had to design something for production in which the fuse characteristics were very critical. So a few comments:

    Fuses aren’t as simple as one might think. A good introduction is

    The current rating on the fuse is the normal rated current that the fuse can handle for typically several hours, not the “blow” or fusing current.

    The opening time is controlled by melting which depends on I^2R energy and is shown on the data sheet in units of amp^2-seconds. For example, a Littlefuse series 326 0.5 amp 250 volt slow blow fuse has a nominal rating of 4.8. So at 1 amp, it will melt in 4.8 seconds. It will actually open a little later due to the time for arcing to stop.

    The data sheet will also have a time-current curve which shows how long it takes to open at various currents. It can be surprising to see how long it takes for a small overload.

    Fuses can be used safely at lower than rated voltage, but never at a higher voltage because they may not be able to interrupt the opening arc at the higher voltage. The maximum interruption current is a separate spec from the current rating.
    Last edited: Jun 18, 2019
  7. WR2E

    WR2E Ham Member QRZ Page

    "about" how much actually is "about 1 amp"?

    What's the rating of that fuse?

    What's the voltage across the fuse?

    See Bob's post directly above...
  8. KA9JLM

    KA9JLM Ham Member QRZ Page

    That is a slow blow fuse.

    What is the current and voltage rating for it ?
  9. W9WQA

    W9WQA Ham Member QRZ Page

    i have a box full,to naked eye they look alike. in magnifier the wire wound look slightly different, they are marked 3/8 to 1.5 amp, 250 v ,"313", whatever that means. the one in pix was burned.. is '313" slo blo?
    measure up to 2 ohms appx.
  10. KA9JLM

    KA9JLM Ham Member QRZ Page

    Yes 313 are slow blow / time delay. They should not be used in a plastic holder. Normally metal clips are used.

    Last edited: Jun 19, 2019

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