My amp is... ALIVE!

Discussion in 'Amps and Cabs [BG]' started by Sunk by Sirens, Mar 24, 2020.

  1. First post...

    I am currently working with a Line 6 LD 300 Pro. Lately, and I can't tell exactly why, it has been turning on effects by itself, and more often than not, it's the filter envelope; usually it sounds like my amp just ate a thick pillow. The knob positions have no bearing on the changes my amp decides to make (i.e. what exactly it decides to eat).

    I already had been having problems in which either the channel volume, overall volume, gain, and/or general EQ is inconsistent when switching between channels. I noticed when I finally got the compatible Line 6 shortboard. That was really going to help me use the effects it has available to their full extent; who plays an entire song with super heavy filter envelope or chorus? Anyway, it's hard to tell exactly what is changing because it's inconsistent. But I'll switch from A to B, and B isn't what it's saved as. I'll switch back to A, and A isn't what it's saved at, even though I was just playing it. I have to cycle between channels a couple times before it decides to load the channel properly. This happens using the shortboard and the amp's own buttons.

    Lastly, it always, ALWAYS, plays show and tell with me when I first turn it on. The audible settings are always in some random, new selection, not corresponding to where the knobs are.

    It's louder than the tiny Fender Rumble that came with my Squier Affinity P bass, so I'll keep using it. But it's harder to rely on it. I already decided I want/need a new amp, but that's gonna take a bit.

    What exactly might be wrong? Can I fix it myself? Will I need to replace something?

    At least it turns on and off when I tell it to.
    mikewalker likes this.
  2. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Do you have the schematics, a scope and/or logic analyzer, multimeter and the knowledge to use them?
    BassmanPaul, dan1952 and Jim Carr like this.
  3. I'll try to find the schematics online (bought the amp secondhand years ago).

    I don't know have nor know how to use a scope or logic analyzer.

    I know how to use a multimeter, and I plan to buy one as soon as the hardware store opens, pending the pandemic.
  4. RSBBass


    Jun 11, 2011
    Just an idea but have you checked to cord and the jack on the bass and amp. Temporary shorting may be sending the signal that turns on the effect. I alawyas try to think of the simple cheap solution first.
  5. seamonkey


    Aug 6, 2004
  6. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    I suggest that you look at the schematic, this is not at all an easy amp to troubleshoot because it's almost entirely DSP driven. Once the input signal is conditioned, just about all of the processing is handled digitally. that includes most of the pots and switches. This is why a logic analyzer and/or scope is important. You need to see what's happening and understand what's supposed to be happening so that you can identify where they don't agree.

    You might get "lucky", but you will discover that it's anything but intuitive.
    dan1952 likes this.
  7. Well I've got some reading to do, that's quite a page-flipper, thanks.

    Step 1: Extricate amp from practice studio.

    Step 2: Factory reset my freshly cleaned and sanitized amp.
  8. Since I plan on replacing this combo amp with a DIY fEARless cab and some-kind-of tube amp head, I don't see the benefit of buying a logic analyzer, but looking at these schematics, I understand the benefit of the tool.
    agedhorse likes this.
  9. Jim Carr

    Jim Carr Dr. Jim

    Jan 21, 2006
    Denton, TX or Kailua, HI
    fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147

    A fEARful is typically DIY because Dave Green, A.K.A greenboy, made his fEARful plans publicly available for free. A Fearless is a newer Greenboy design. It is proprietary with plans available only to licensed builders, and thus, by definition cannot be DIY.

    fEARful or Fearless, you will not regret using such a cabinet. I like the Mesa Prodigy tube head with a 12/6/1, but perhaps this is a discussion for a different thread?
  10. :wacky: Ah, typo, I meant fEARful. Yes, I actually know the difference. I specified DIY because I know there are a few authorized dealers who sell completed fEARful cabs and/or build kits. :thumbsup:

    I'll try to dig around with the search function and figure out some of the nitty gritty, but if I can't find what I'm looking for, then yes I'll start a separate post for that discussion. At the very least, I'll post a "build-ography" that follows my process.

    Even if I get a new amp/cab soon, I want to attempt fixing this Line 6 combo before selling it.
    Jim Carr likes this.
  11. Might as well set it on fire as try to scope it with a multimeter.
  12. Do you or have you ever plugged in an FBV pedal to that amp? It goes into the RJ-45 jack on the front.

    Shine a bright flashlight into the jack and look at it with as strong a magnifying glass as you can find. See if the wire "tines" have turned green, black, or have any kinda fuzz on them. If so, take it to a repair person and have them clean those tines in the jack and see if the amp still does things on its own. Those little metal tines can grow garbage on them and sometimes it pushes them together and shorts them, or causes some intermittent connections. It's a terrible design.

    If not, continue on with testing equipment and the repair manual, or set it on fire - but if you set it on fire do it in an open field - there's lots of potentially fire-toxic junk in that box... ;-)

    Side note: Those amps are Pre-Yamaha and the guys who used to write the manuals had a bit of a sense of humour. I'll always remember the manuals for the LD and HD amps listing the dials and switches. When they got to the power button, they had something like "Power Switch: The Amp sounds better with this set to "ON". - That was actually debatable.
    Last edited: Mar 25, 2020
    cool breeze, mikewalker and PaulCISSA like this.
  13. Yes, as I said in OP, I only really started to notice the issue of the channels loading inconsistently whenever I tried out the FBV Shortboard.

    I know all about how toxic electronics can be, particularly when combusted...

    Gonna get together with my band's drummer at the practice space later today, and then I'll try all the easy troubleshooting tips.

    I originally bought it for ~$250 off some local high school kid who ended up not liking bass or something crazy like that. Luckily I was able to make more than that playing all the gigs I have with it.
    mikewalker and frankie5string like this.
  14. Sorry, somehow I missed the bit about you actually using the floorboards <facepalm> ...

    You can also damage the input by using the floorboard. It's got very little protection from static/shorting.

    Good luck and let me know how you make out - I'm always surprised when someone mentions they're still using them - they really weren't very robust.
    mikewalker likes this.
  15. Eddie LeBlanc

    Eddie LeBlanc

    Oct 26, 2014
    Beaumont, Texas
    Don't create no problem, won't be no problem.
    Maybe try this.... if all else fails...... Sorry couldn't resist....

    TheReceder, mikewalker and SactoBass like this.
  16. cableguy


    Jun 4, 2009
    North Bend, WA
    If you want to play around with the amp to try and fix it, go ahead. But if it were me I would probably just replace it and start your fEARful build. Your time would be better served with that. I don't know what your financial situation is, but that would be my plan. TB classified is full of used bass heads at all price points.
    Bill Whitehurst likes this.
  17. Thanks for posting that. I've always wondered how the Line6 amps do their thing but wasn't ever quite curious enough to actually go find a schematic.

    OP: Agedhorse is right, you won't get anywhere on this amp without, at the very least, a digital oscilloscope. One thing you can try is a different FBV pedal to make sure yours isn't defective.
    dan1952, seamonkey and agedhorse like this.
  18. Your amp is ALIVE???

    RUN - EVERYBODY RUN!!! IT's the attack of the living amp!
    dan1952, BioWeapon and mikewalker like this.
  19. Oh wait, it's a line 6. Now I get the problem.

    I have had nothing but reliability issues from every line 6 amp I've ever owned. so frustrating. best of luck to ya though!
  20. SactoBass

    SactoBass A retired civil engineer who likes all-tube amps! Supporting Member

    Jul 8, 2009
    Lake Havasu City, AZ