Markbass F1 Issue: Help!

Discussion in 'Amps and Cabs [BG]' started by reddenedxsky, Dec 30, 2015.

  1. Hey guys! A few months ago I bought an F1 from another TB member, it worked flawlessly at first, but now it will cut out if I bump the input jack on my bass while playing. At first I thought it was the jack on my bass, but after trying multiple basses and cables I always have the same problem. If I turn the head off and back on again, it's fine. Until I bump the jack on the bass again.

    My band has a few big shows coming up and I definitely want to avoid having to run over and turn my F1 on and off again in the middle of a song.

    Anyone have any suggestions or have the same problem? :)
  2. Do you know if the DI is still working after the "cut out"? And what kind of cabinet (and impedance) are you using?
  3. I don't know about the DI, but I'm running through a dB technologies 410 and 210 (these cabs are over 20 years old). both are 8 ohm, but it still happens if I only run through one. So at 4 and 8. Any ideas? Thanks for the help! Also this is not using any effects. Plugged straight in to the head.
  4. BassmanPaul

    BassmanPaul Inactive

    I’m stretching here but if the unit has an effects loop try linking the send and return with a signal cable. See if the problem still occurs. Probably it will but at least worth a try.
    B-string likes this.
  5. B-string

    B-string Supporting Member

    Sorry I have no idea how bumping the jack on a bass could kill the output of an amp. Coincidence maybe?
  6. @B-string I highly doubt it as I've tried a few different basses and cables, and I can replicate it most of the time, I just don't know what could be causing it. I'll try that @BassmanPaul and update soon! My rig is at my guitar players house, so it may not be for another day.
  7. B-string

    B-string Supporting Member

    Make sure it is not the cable rattling the plug at the amp (you said most of the time, not all the time). The nut on the input jack should be snug (better than finger tight). IF that jack's nut is loose you could have broken solder joints on the preamp board at that jack (solder touch up).
    Last edited: Dec 30, 2015
    murphy likes this.
  8. Others here are certainly more versed on electronics, but I've experienced a Markbass cutting out. The reason I asked about the DI and your cabinet use is that, if the DI still works, I believe that points to the amp's current protection mode, which is tripped by an impedance dip/current spike beyond a set threshold. The preamp doesn't shut down under current protection, only the power amp. A thought was that, if you were running at a nominal 4 ohms, you might be in a constant state of hovering right around the threshold, and possibly something with the bumping was instantaneously/momentarily pushing it past it. Since it's happening at 4 or 8 ohms, the hovering right at the edge part of that is blown out of the water.

    What's happening seems to be input-based rather than output-based, but it would probably to be good to know what kind of shut down is occurring. I'd suggest causing it to happen to check the DI. If the preamp section isn't working, I'd think that would be a good piece of information to have in tracing down the cause.
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