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amp cutting out?

Discussion in 'Amps and Cabs [BG]' started by Mr_Shrapnel, May 9, 2005.

  1. Mr_Shrapnel

    Mr_Shrapnel Guest

    Mar 20, 2004
    hey, my current set up is a laney rbh800 head, hughes and kettner br 410 h cab, and fender precision bass.

    basically whenever i play, every now and then I get a really crackly sound coming from my cab, and the sound starts to fade out until it totally cuts out. then a few minutes later, the sound gradually gets louder and louder, until its back up to full volume again (best i can describe it).
    This is soooo irritating cos i just got em! So does anyone have any ideas what it could be? all items are second hand, and im sure its not the bass itself, so it must be the amp right?

  2. Joe Nerve

    Joe Nerve Supporting Member

    Oct 7, 2000
    New York City
    Endorsing artist: Musicman basses
    I had a hartke that did that and it was the fuse. Check to see if its in tightly (if it has a fuse). It may be vibrating loose. If that ain't it I dunno.

    edit: Just reread your post, the hartke actually simply didn't work - didnt do the fade thing you describe. Ya might want to check anyhow.
  3. Mr_Shrapnel

    Mr_Shrapnel Guest

    Mar 20, 2004
    oh ok, tbh i try anything! u mean a fuse in the plug or the actual amp its self?
  4. Folmeister

    Folmeister Knowledge is Good - Emile Faber Supporting Member

    May 7, 2003
    Tomball, Texas
    Is the amp solid state or tube?
  5. Mr_Shrapnel

    Mr_Shrapnel Guest

    Mar 20, 2004
    Its solid state - it is second hand, but its not very old, and in good condition. but its gota be the amp. oh yeah, another thing is, if its starting to cut out, and i switch the amp off, then back on, it will be fine again.

    its almost like when a computer crashes, if u switch it off, then back on, its all ok once its re-booted. (generally...hehe)
  6. A defective power switch, maybe?

    Or an output transistor that's going south, but coming back to life after a brief cool-off....
  7. Mr_Shrapnel

    Mr_Shrapnel Guest

    Mar 20, 2004
    yeah maybe. i mean i really have no idea, but to be honest im gona take it in to a shop n see what they think, but id kind of like an idea of what i cud b, so i dont walk in there not knowing what to say. so any suggestions of what it cud b would help loads! or if anyones had a similar thing happen to them.
  8. 44me


    Jun 17, 2002
    Bedford, NH USA
    I don’t think it’s a damaged transistor. That’s usually a more definite failure. It sounds more like a capacitor going bad, or maybe a cracked solder joint. Definitely bring it to a shop with a good tech.

    - John
  9. LoveThatBass


    Jun 28, 2004
    Or defective Jack or Pot in need of cleaning.
  10. Mr_Shrapnel

    Mr_Shrapnel Guest

    Mar 20, 2004
    hmm well ill take it to a shop this wknd n let u guys know what they say, just in case anything like this happens to u. Another thing ive noticed is that if you touch either the main gain or enhancement knob, i can hear a humming/buzzing sound, kinda as if it wasnt ground properly, but thats funny cos generally if something not grounded, the humming goes when u touch it right?
    i also get a really nasty buzzing when i turn the tone up on the bass itself (luckily i always have the tone at the minimum)
  11. 44me


    Jun 17, 2002
    Bedford, NH USA
    You’re likely looking at two different problems. I shielded my P-bass a few years ago and it greatly reduced the hum with the tone control opened up.

    Grounding usually does reduce hum. However, the hum reduction you get when you touch the strings is not from you grounding the bass, but rather the bass grounding you, or at least getting you to the same potential as the amp ground. Just standing in a room, your body picks up AC voltage from the wiring that’s all around us. If you and the amplifier are not at the same potential, you can easily inject a signal from this voltage difference into the pickup/wiring, particularly if the bass is poorly shielded. Likewise, the same thing can happen when you touch an amplifier control pot. A good (and properly functioning) design should minimize this effect.

    - John
  12. Mr_Shrapnel

    Mr_Shrapnel Guest

    Mar 20, 2004
    yeah, the funny thing is, ive got an old peavey amp combo (tko 65) and if i plug my bass into that and crank up the tone, there is a slight hum (as there naturally would be) but its NO WAY near as loud as when its coming from my laney/hughes & kettner setup. that leads me to the conclusion it must be the amp. and its not that ive got the gain up too high, cos ive got that real low, but just have the volume up.
  13. 44me


    Jun 17, 2002
    Bedford, NH USA
    Yes - it definitely sounds like something is wrong with your amp, so I'd get that fixed before thinking too hard about anything else. Let us know what they find wrong with it.

    - John
  14. Mr_Shrapnel

    Mr_Shrapnel Guest

    Mar 20, 2004
    hmm ive just found something a lil strange (maybe) when my amp was cutting out i did have the bass on the eq up full, now ive read somewhere that the bass eq settings suck alot of wattage up...so ive turned the bass down a few notches, and have been playing for a couple of days with no sign of the amp cutting out! now its not exactly a perfect test, cos the whole cutting out this was kinda random.....but quite frequent, and i would have thought it would have happened by now.
    so do you guys think, that having the bass set up that high, could cause it to fade in and out like ive described?

    Though there is still the matter of the hum…
  15. with my Fender BXr400. It turned out to be a combination of a dirty crossover switch and several poor solder joints. I fought with the amp for months before I sent it to the shop. I think the repair bill was $48.00.
  16. Mr_Shrapnel

    Mr_Shrapnel Guest

    Mar 20, 2004
    yeah its just strange that now ive turned the bass setting down a little, it seems to have stopped (well...so far anyway)
  17. epsilonbass


    Dec 5, 2004
    Sorry to resurrect an old thread but i used the search before posting.

    I'm having the same problem with my hartke head. The strange thing is it only happens at shows. I'll have a three hour practice a few days a week, and the amp never gives out.

    But at shows, in the middle of a song the amp will fade out, and after about 30-60 seconds will just fade back in. It of course is a very bad problem for shows. I'm nervous about bringing it in somewhere to have it looked at, because I suspect that they will play with it for five minutes not find anything wrong and charge me 100 bucks for just looking at it.

    Any suggestions?
  18. thumpbass1


    Jul 4, 2004
    It's no fun sorting out these kind of problems. I'm suspecting
    you probably need some solder joints and traces redone but
    I also have another trouble shooting area that gets missed
    so often that sometimes even good amp techs miss it once
    in awhile. It could be the effects loop if your'e amp has one!

    I had a solid state amp that did the same sort of thing your
    Laney seems to be doing and it drove me nuts as my tech
    went over and fixed up a few spots that needed to be done
    but the amp pulled off the intermitent crackling and buzzing
    thing before the sound cut out entirely after I'd had the amp
    gone over! I called my tech and he said to fire it up again
    and if it did the same thing he wanted me to put a short
    instrument cable in the fx loop to jumper the send back into
    the return jack. Well that was it! I had a dirty fx loop! It
    was the scource of the problem and with some contact
    cleaner I was on my way to fixing it.

    I would at least test your fx loop as a possible cause to your
    troubles. That said it never hurts to have a tech give a look
    at your amp as even if you spend 50 or so bucks it's still
    chaper to repair a good amp than to buy a new one. I wish
    you luck.
  19. Check if the heat sinks are clogged. Sounds to me like a heat problem. Is the fan actually running?

  20. 44me


    Jun 17, 2002
    Bedford, NH USA
    What’s different between rehearsals and shows? If your effects loop is different, that’s a likely cause as thumpbass has pointed out. Seems when I’ve seen guitar player’s amps cutting out, the effects chain is the problem 9 out of 10 times. On the other hand, if volume level is the only difference, it most likely is an over-heating problem. I'm with Bassmanpaul on this. Your description of fade-out then fade back in after 30-60 seconds really sounds like a thermal protection circuit doing its job. Grime and dust built up on heat sinks and fan blades definitely hurts cooling performance, so the first thing is to make sure everything is clean. Then makes sure the fan works. Is there anything that would make you think you are pushing the amp harder at shows than you have in the past (bigger room, louder band, etc.)? I had an amp that used to cut out occasionally at gigs. Then we replaced the drummer and it never cutout again. There’s not a huge difference in perceived volume between where your amp is coasting and where it’s ready to fry eggs.

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