EVM12L | The Canadian Guitar Forum

EVM12L

Discussion in 'Amp Building/Technical/Repair' started by Theon, Jan 3, 2020.

  1. Theon

    Theon

    Joined:
    Nov 14, 2017
    Location:
    Detroit
    Trying to diagnose a problem with my speaker.
    Touching 9 volt battery to ground and neutral wire caused cone to pulse.

    Placed input jack leads into compression tabs.
    Plugged cable in no energy or sound.
     
  2. oldjoat

    oldjoat

    Joined:
    Apr 4, 2019
    Location:
    lost in time and lost in space RHPS
    ummmm ... a bit cryptic

    the 9V has enough power to move the speaker . ( so speaker is working )

    input jack leads ( from guitar I'm assuming ) doesn't have enough power to move earphones , let alone a larger speaker .
    or if it's a speaker patch cord , the jack end may be broken internally or shorted. test the cord with a meter .

    try using an old radio to power the speaker instead .

    or use another known good amp, disconnect the internal speaker and run 2 wires out to the speaker .

    some pic's would be nice .
     
    Theon likes this.
  3. greco

    greco Gold Member

    Joined:
    Jul 15, 2007
    Location:
    Kitchener, Ontario
    For sure!
     
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  4. Theon

    Theon

    Joined:
    Nov 14, 2017
    Location:
    Detroit
    o_O "Umm .. a bit cryptic"
    I know!
    Attached ground wire (Black) to input jack ring then neutral wire (Red) to input jack hot.

    Plugged cable from amps external speaker jack into extension cabinet. No sound!

    I have switched the cables from one jack to the other on the amp. Combo cabinet speakers attatched to amplifier have sound with both connections.

    Using an empty (no chassis) combo cabinet underneath a head.
    Connecting the 2x12 speaker with a split cable.

    Here is a photo of the setup I am trying to hookup to the extension cabinet.
    [​IMG]


    I have since taken the wiring harness apart.
    Try to reattach and snap a photo to upload.
     
    Last edited: Jan 3, 2020
  5. greco

    greco Gold Member

    Joined:
    Jul 15, 2007
    Location:
    Kitchener, Ontario
    Your pic wasn't clear so I reposted it here.

    Why not wire the speakers together in series or parallel and then run one (single) speaker cable from one of the speakers up to the amp?
    What is the impedance (in ohms) of EACH speaker? This is important to know for the wiring.

    [​IMG]
     
    Last edited: Jan 3, 2020
  6. Theon

    Theon

    Joined:
    Nov 14, 2017
    Location:
    Detroit
    "Why not wire the speakers together in series or parallel and then run one (single) speaker cable from one of the speakers up to the amp? What is the impedance (in ohms) of EACH speaker? This is important to know for the wiring".

    Thank you for reposting the photo Greco.

    Amp head and 2x12 speaker cabinet in the photo is my everyday combo. They work fine together.

    I am trying to test an extension cabinet with the amps external speaker output. 1x12 extension cabinet is a repair project I am finishing up.
    Want to see if it functions properly.
     
  7. greco

    greco Gold Member

    Joined:
    Jul 15, 2007
    Location:
    Kitchener, Ontario
    No problem. Beautiful looking gear!

    OK. The wiring looks unusual/atypical to me...but if it works fine, all is well.

    Can you take a pic of how it is wired? ...or is it working now?
     
  8. Theon

    Theon

    Joined:
    Nov 14, 2017
    Location:
    Detroit
    It's working fine. The cabinet I need to upload a photo of is the problem.
     
  9. Granny Gremlin

    Granny Gremlin Gold Member

    Joined:
    Jun 3, 2016
    Location:
    Toronto - Riverside
    Can't quite see the pic too well, but it looks like the harness from the amp to the ext cab is like a Y cable. Assuming that is parallel wiring for the 2 speakers ( more standard/common), but if for some reason it is series that would explain why it doesn't work with only a single speaker plugged in (need both speakers connected to complete the circuit). And that's assuming I understand the description of what was attempted correctly - which I am not sure I do.

    I recommend you mimic that setup pictured above with the ext cab, but instead of using that existing cable, find the shortest 1/4" cable you have that's long enough (even a guitar cable) that is known to be working (test it) and use that. You can kludge some leads onto the 1/4" jack on the other end if you don't wanna rip it off bc you don't solder (if you do solder just wire up a 1/4" jack to 2 wires). I'd use alligator clip leads that I have, but even some bare wire, 1 ea, wrapped around tip and sleeve of the jack at the speaker end (tape up the sleeve one to keep it in place and insulate from the tip, which will stay put on account of the indent) will do to prove the point.

    ... wait does the ext cab already have a 1/4" input wired up? if so try that (again with any old guitar cable - won't hurt it and tone suck is not an issue right now). If that doesn't work then as above connecting direct to the speaker.

    That'll tell you what the issue is.
     
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  10. greco

    greco Gold Member

    Joined:
    Jul 15, 2007
    Location:
    Kitchener, Ontario
    OK ...Sorry...My misunderstanding.
    If I send you a PM with my email address, do you have a pic you can send me?
    I'll post it for you.
     
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  11. jb welder

    jb welder

    Joined:
    Sep 13, 2010
    Location:
    Melonville, Canada
    One thing I will say is if that is the head you are using, there must always be something plugged into 'main' speaker jack. If 'main' is empty, and you plug only into 'ext', there will be no sound.
     
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  12. Theon

    Theon

    Joined:
    Nov 14, 2017
    Location:
    Detroit
    @Granny Gremlin
    Thanks for your reply and info.
    The extension cabinet I am trying to test was damaged in shipping. It's a project.

    I just checked the EVM12L speaker wires and believe it was incorrectly wired to the old input jack.
    Plan to give it another go tomorrow.
     
    Last edited: Jan 3, 2020
  13. greco

    greco Gold Member

    Joined:
    Jul 15, 2007
    Location:
    Kitchener, Ontario
    Good Luck with it. Please let us know.
     
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  14. Theon

    Theon

    Joined:
    Nov 14, 2017
    Location:
    Detroit
    Thank you for the reply and info @jb welder!

    Yes I am aware the main speaker jack must always have an input.
     
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  15. Theon

    Theon

    Joined:
    Nov 14, 2017
    Location:
    Detroit
    Thanks for your offer @greco!
    Using Photobucket now. Posting a photo tomorrow.
     
    greco likes this.

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