Ashdown ABM evo iii volume problem

Discussion in 'Amps and Cabs [BG]' started by hardcorexpato, Feb 18, 2017.

  1. hardcorexpato


    Feb 18, 2017
    Hey everyone!
    I recently have been having trouble with the ashdown abm head. in the beginning of rehearsal, it sounds great and has plenty of volume. after a bit of playing the volume will drop and i have to really crank it to get the volume at a good level. I have already opened it up and switched out the preamp tube and it still drops in volume. Do you think there is something I can do before I take it in to a tech? any advice will help, or if you can point me in the right direction i would appreciate it. Thank you!
  2. eKay


    May 8, 2014
    No answer on this? I am having the exact same problem. It happened during my first gig with the head. I had the input and output cranked all the way up and I could barely hear it with the rest of the band going. Good thing I also was going into the PA.
  3. Did the level drop in the PA?
  4. eKay


    May 8, 2014
    For me? No. It happened pretty suddenly in the middle of a song, the volume just dropped. Different basses, different cords, fiddled all the controls, no difference, and no crackling sound that would indicate a dirty pot or something. It still sounds great, but when the master is all the way up, it sounds like it's on "1". I've seen some posts on these amps where they have cheap fuses, but this is not the behavior I'd expect.

    I haven't totally ruled out the cab, I must say. Will check on that as well. But, and maybe this is a clue, the VU meter is not bouncing very high anymore either. Seems like I was able to pin it before on certain settings.
  5. eKay


    May 8, 2014
    I wanted to follow up here about my Ashdown. Turns out there was no problem with the amp! One of the speakers in my Goliath II came unplugged, and the fuse inside was barely hanging in its socket. As it was, only 2 of the 4 speakers were working. All's well now.
  6. hardcorexpato


    Feb 18, 2017
    I wanted to follow up as well...

    I ended up taking the amp to an amp repair shop here where I live and they told me that the amp was pretty dusty inside and some of the ribbon cables were touching etc... just needed overall maintenance I guess but nothing big was changed. No tubes were changed out or anything big like that just overall cleaning I guess. My amp is fine now, too.
  7. chevaliernoir


    Aug 1, 2016
    I have the same issue.
    The input level is very low.
    I need to put gain at maximum to get a reasonable output, avec using active bass (with battery in good condition).
    I checked inside. It is clean.

    I thought maybe it's just a matter of VU meter, but even with Gain at maximum, I have no saturation at all.

    With and Without SHAPE, the signal amplitude is almost the same...
    With and Without EQ (flat) the amplitude is the same too.
    With and without the Lamp, the amplitude is almost the same too...
    The Passive/Active works as it should (Very high input impedance in Passive; 20K in active; amplitude devided by 2 in Active)

    As the Vu meter is very low, even with maximum input Gain, I imagine the problem comes between the input and the EQ.

    I suspect the input JFET :
    I measured 3V on R24 (so there is 3mA in transidtor)
    I confirmed 3V on R46
    Fet Gate is at 0V (seems normal for me)
    Source is at 2.1V

    I do not see the reference of the TR4 FET . Any idea.
    Vgs at 2.1 sounds OK for you?

    Next check will be the IC3 amplifier, where Gain should be at ~20