Combo complications

Discussion in 'Amps and Cabs [BG]' started by Oysterman, Jan 11, 2001.

  1. Oysterman


    Mar 30, 2000
    Howdy guys and gals.

    For a week now, I have been awaiting reply from the manufacturer of my combo amp, and since I am quite impatient by nature (and quite lost when it comes to tech issues of this kind), I thought maybe the fellow TalkBassers could help me somewhat.

    You see, my combo is not functioning properly. It is not all dead, but not far from. The problems have evolved during rehearsal, that the sound would come on and off seemingly when it wanted to... at first, it was just occasionally and I blamed the old cord I have and used another (a new one), but the problem wouldn't go away. Instead it went out more and more often, and suddenly I couldn't get it to sound. At least not much.

    * The input jack. All of a sudden, I am not able to insert the cord into the jack. To be able to do so, I have to loosen the screw nut around it. What's with that?

    * When I try to get it to sound, all that comes out from the speakers is a very weak, distorted signal.

    I just wonder what might be going on. Possible causes would be:

    * Power amp blown - I sure as heck wouldn't want this... and I can still use the output volume control, so that couldn't be it, right? Then it wouldn't sound at all, or...? Oh lord, I fear the worst... :(

    * Some kind of wiring damage between the power amp and the speakers (this would be an easy fix, I guess).

    * Not enough contact in the input jack, so just fixing the input would clear all my problems.

    Any thoughts on this? I would like to be able to have a diagnose before I go to a store to have them repair it - would save them time and me money...

    Sorry if I'm being too long-winded.
  2. Hey there Oysterman,
    By the sounds of it, the input jack is the most likely culprit. If you're having trouble inserting the cable from your bass, there's definately something wrong with the input jack. This would cause the symptoms you're seeing (hearing). You may just need to replace the input jack. 90% of problems with electronics can be traced to bad cables, wiring, or solder joints so your power amp probably isn't blown.... of course dagnosing amp problems without seeing the amp is an imprecise science at best. My advice would be to get it to a reputable tech soon and have them look at it. cheers!
  3. notduane


    Nov 24, 2000
    I agree with Spacegoat ~ probably the input jack.

    Maybe you're thinkin' of somethin' else while plugging-in & un-plugging? :p

    Take it to a tech if it's still under warranty.
    Otherwise get a decent replacement (e.g., Switchcraft) and do it yourself.
  4. Oysterman


    Mar 30, 2000
    Thanks fellas,

    I tried it again, just recently... I've tightened the input jack nut, and with a little technique I actually *could* insert the cord plug... but the amp was still dead. I turned up the volume more and more and presto! There was sound! It seemed to be working all right, just as good as before it went haywire. I was overjoyed, I tell you, but after five minutes of playing it just went silent again. :(

    So, it's not the power amp, and, although not in perfect condition, the input jack seemed to function properly. And wires and solder joints don't pop in and out "just like that", do they?

    I'm puzzled.

    :D Har har har har... you have a dirty mind, mister! :p

    Unfortunately the warranty expired like 5-6 years ago :p, so any tech job could cost me a small fortune... of which I really do not possess. :(

    Reputable tech? Around here? Heh, I am yet to meet one... :rolleyes: Well, at least I could try...
  5. rockthistown


    Jan 8, 2001
    it is also possible that the pots may be dirty. my marshall jcm900 does that all the time. what kind of amp is it?
  6. notduane


    Nov 24, 2000
    rockthistown has a good point, i.e., the pots may be dirty.
    Stew-Mac has some aerosol "blowers" to help clean them.
    Solder joints can be intermittent if they're "cold".
    You could try re-flowing the joints.
    Make sure there's a good mechanical connection
    between the wire(s) and the jack lug(s) also.
    Ruh-roh! :eek: I better get myself to the Bored of Mental Hygeine for a good scrubbin' :p
  7. I had this problem a couple of years ago with an old amp.I guess we are talking solid state here? Anyway the problem with my amp was just the same as with yours.. it worked fine and all of a sudden it went silent, or at least very low in volume and it also distorted. So I tried to figure out what it was, noticing that the powerpart of the amp got VERY hot.

    Finally I found out what caused the problem, it was a short in the speakercable.. due to me being sloppy when putting it together. Fixed it properly and it was fine and has been everafter.. but I dont use that amp anymore unless I really have to. So check the speakercable for shorts, that is my tip.. you may also considering changing the input jack, you dont want it to go bad on you at a gig do you?:mad:

    Good Luck! :)
  8. Oysterman


    Mar 30, 2000
    Bumping this up again.

    I had it fixed for a decent sum of money (600 SEK = around 60 USD). Apparently, it was some solderings on the circuit board that were at fault, and the input jack was replaced.

    First, there was some strange buzzing coming out of it when playing. It was as if something were loose in the combo, and vibrating with the bass frequencies. Not feeling too good about it, I cursed the repair tech and decided to return it and make a complaint after the rehearsal I had one day.
    At the rehearsal, the problem was still there but not really noticeable when playing fairly loud. But, and here's the funny part; at the end of the rehearsal the buzzing had stopped! It sounded as clean and smooth as it always had before! Kind of scares me, it seems to live it's own life... never before had I experienced that an amp got better when played through for a while. As if the supposed loose part popped back in place, just like that!

    Anyhow, I'm back on dry land again. I just love it when it all turns out well in the end. :)
  9. Oahh another happy ending.. :)

    About getting better beeing played..its almost like my amp, the fan rattles when beeing started up but when its been on for say 5 mins its running nice and quietly. Better than the other way around ;)