Results 1 to 12 of 12

Thread: Which fuse ?

  1. #1
    Member
    Join Date
    Jun 2008
    Posts
    51
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    12

    Which fuse ?

    My Mision Amps DIY 5E3 is completely dead (after sitting in the attic for several months). I suspect a blown fuse. I know from the schematics it should be 2A, but are there other specs I should look for when I go out to buy some?

    - Koen.

    0 Not allowed! Not allowed!

  2. #2
    Old Timer soundguruman's Avatar
    Join Date
    Jul 2011
    Location
    California
    Posts
    2,522
    Thumbs Up/Down
    Received: 5/0
    Given: 0/0
    Rep Power
    11
    Quote Originally Posted by koen View Post
    My Mision Amps DIY 5E3 is completely dead (after sitting in the attic for several months). I suspect a blown fuse. I know from the schematics it should be 2A, but are there other specs I should look for when I go out to buy some?

    - Koen.
    I think it's 3AG, 250 volt, 2 amp, slow blow fuse, but you could ask Bruce at Mission Amps, to be sure.

    0 Not allowed! Not allowed!

  3. #3
    Senior Hollow State Tech Bruce / Mission Amps's Avatar
    Join Date
    May 2006
    Location
    Denver, Colorado
    Posts
    3,045
    Thumbs Up/Down
    Received: 7/0
    Given: 0/0
    Rep Power
    17
    Yes, 3AG @ 2 amps slo-blo or MDL.
    Actually, a good running 5E3 won't blow a 1a slo-blo fuse either.... but a bad power tube or a short somewhere will blow 3 or 4 amp fuse.

    Be careful though... sitting doing nothing for a few months... and then blowing a 2 amp fuse when firing it back up sounds suspicious.

    0 Not allowed! Not allowed!
    Bruce

    Mission Amps
    Denver, CO. 80022
    www.missionamps.com
    303-955-2412

  4. #4
    Old Timer soundguruman's Avatar
    Join Date
    Jul 2011
    Location
    California
    Posts
    2,522
    Thumbs Up/Down
    Received: 5/0
    Given: 0/0
    Rep Power
    11
    That's a very good point, all too often ignored.
    When your amp blows a fuse, you need to figure out what makes it blow.
    Instead of just putting another one in, and blowing it again.
    How many amps is a gum wrapper?

    0 Not allowed! Not allowed!

  5. #5
    Member
    Join Date
    Jun 2008
    Posts
    51
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    12
    I don't know if it was a blown fuse, that was just a guess. I haven't had the time yet to look at it again, hopefully more in the next couple of days.

    Anything else I could check?

    And I don't know the answer to soundguruman's question about the gumwrapper...

    0 Not allowed! Not allowed!

  6. #6
    Senior Hollow State Tech Bruce / Mission Amps's Avatar
    Join Date
    May 2006
    Location
    Denver, Colorado
    Posts
    3,045
    Thumbs Up/Down
    Received: 7/0
    Given: 0/0
    Rep Power
    17
    Quote Originally Posted by koen View Post
    I don't know if it was a blown fuse, that was just a guess. I haven't had the time yet to look at it again, hopefully more in the next couple of days.

    Anything else I could check?

    And I don't know the answer to soundguruman's question about the gumwrapper...
    In the old days it was common to find an amp with a blown fuse wrapped with the foil wrapper from a strip of gum... the foil bypasses the blown fuse.

    At this point, and you guessing, I don't know that the fuse is blown... you could even have a bad outlet... or the amp wasn't plugged in all the way... etc.

    Pull all the tubes out and put a new fuse in. Restart the amp with no tubes and see if it lights up.
    If yes, put the rectifier tube in and see if it lights up or blows the fuse.
    If OK, put the preamp tubes back in... if OK, put the power tubes back in.
    If it blows the fuse during any of those steps then you have a little work to do trying to figure out what the load of that test would do to cause a current surge.

    0 Not allowed! Not allowed!
    Bruce

    Mission Amps
    Denver, CO. 80022
    www.missionamps.com
    303-955-2412

  7. #7
    Old Timer soundguruman's Avatar
    Join Date
    Jul 2011
    Location
    California
    Posts
    2,522
    Thumbs Up/Down
    Received: 5/0
    Given: 0/0
    Rep Power
    11
    Relax, if you don't know about the gum wrapper, you can use a penny instead.

    0 Not allowed! Not allowed!

  8. #8
    Member
    Join Date
    Jun 2008
    Posts
    51
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    12
    A quick update.

    I stopped by RadioShack on my way home yesterday and got 2A sloblo fuses. But they are too small and don't fit.... grrrr I hate that store. So until I have the correct fuses, I won't be able to do more testing. I'm hesitant to use a gumwrapper or penny to bypass the fuse

    0 Not allowed! Not allowed!

  9. #9
    Supporting Member Jazz P Bass's Avatar
    Join Date
    Dec 2008
    Location
    Wernersville, PA
    Posts
    12,827
    Thumbs Up/Down
    Received: 449/2
    Given: 236/0
    Rep Power
    25
    Don't know why your are dissing Radio Shack.
    You bought the incorrect fuse.
    1 1/4 x 1/4 is pretty "standard" on tube amps.
    2.0-Amp 250V 1x" Slow-Blow Fuse (4-Pack) - RadioShack.com
    Although some amps require the smaller 5x20 mm (metric) fuses.

    0 Not allowed! Not allowed!

  10. #10
    Member
    Join Date
    Jun 2008
    Posts
    51
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    12
    Ok, I feel incredibly stupid. When I flipped the amp on, I flipped the standby switch instead of the power switch. No wonder it wouldn't turn on. That happens when you don't use it for 6 months...

    At least I got a set of spare fuses now

    0 Not allowed! Not allowed!

  11. #11
    Senior Member
    Join Date
    Feb 2009
    Posts
    519
    Thumbs Up/Down
    Received: 22/0
    Given: 25/0
    Rep Power
    11
    wow, that's pretty bad. a happy ending nonetheless.

    0 Not allowed! Not allowed!

  12. #12
    Senior Hollow State Tech Bruce / Mission Amps's Avatar
    Join Date
    May 2006
    Location
    Denver, Colorado
    Posts
    3,045
    Thumbs Up/Down
    Received: 7/0
    Given: 0/0
    Rep Power
    17
    Ha ha... I guess I should ink the chassis so it says On-Off and standby somewhere by the switches....

    0 Not allowed! Not allowed!
    Bruce

    Mission Amps
    Denver, CO. 80022
    www.missionamps.com
    303-955-2412

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Fuse Help
    By xampworshipx in forum Vintage Amps
    Replies: 8
    Last Post: 02-23-2010, 06:07 AM
  2. Which fuse to use...???
    By acorkos in forum Build Your Amp
    Replies: 2
    Last Post: 09-03-2009, 03:42 PM
  3. Rectifier fuse?
    By Axtman in forum Theory & Design
    Replies: 3
    Last Post: 06-11-2009, 09:20 AM
  4. Fuse rating
    By 62strat in forum Music Electronics
    Replies: 6
    Last Post: 08-23-2008, 03:36 PM
  5. Possible blown fuse...?
    By madpigpunk in forum Maintenance, Troubleshooting & Repair
    Replies: 2
    Last Post: 10-09-2007, 05:30 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •