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The ongoing saga of the noisy Peavey Combo 300

Discussion in 'Amps and Cabs [BG]' started by mariner, Feb 28, 2005.


  1. mariner

    mariner

    Feb 18, 2005
    Front Royal, VA
    Well, I've been to a local shop and followed some suggestions for cleaning the amp. Here are my symptoms, if anyone can offer any advice on whether this thing is toast or worth salvaging, please chime in....

    1. The 1st 2 or 3 minutes I play, it has a muted tone. As soon as it appears to warm up, something happens and the tone fattens and distortion starts. Any long tones sometimes clip themselves or fizzle away.

    2. Once warmed up, the hum is very noticable unless I turn the Pre-Gain really low. Mind you, Peavey's recommended settings are Pre-Gain on 4 and Post-Gain on 7. At those levels the hum is annoying until I touch my bridge or the strings.

    3. I have a P-style bass (Hondo fame w/ Basslines QPs), I noticed that the top pup was very high, I lowered it quite a bit to even the distance from the strings thinking the closeness was overbearing for the amp and that didn't make any difference.

    4. I have a Hartke 1415 that doesn't portray any of the hum that I here on the Peavey. Newer technology maybe???

    If anyone can surnise anything from these symptoms, please offer some suggestions....
     
  2. xb100

    xb100

    Mar 24, 2004
    NH, In
    Well i when i went and got my tnt 115, it was plugged in right next to a neon sign and got alot of buzz from that. Maybe the combo was next to some lights or something?

    I play my tnt with a jackson 5 string with active pups what i do is turn the trble and bass down half way and have everything set flat. I might boost the mids a little but other than that i get no hiss and it sounds great.
     
  3. Unscrew the head from the chassis, pull it out, clean off all dust and stuff, slide it back in and retry it. It usually works for peaveys that have that loud hum and stuff.
     
  4. Selta

    Selta

    Feb 6, 2002
    Pacific Northwet
    Total fanboi of: Fractal Audio, AudiKinesis Cabs, Dingwall basses
    Since it goes away when you touch your bridge/strings etc, that means you have a bad ground somewhere. Either 1) take it apart and find it and fix it, or 2) take it to someone, tell them, and have them look for a bad ground. It has to be the amp since you said it doesn't do it on the other amp.

    Ray
     
  5. mariner

    mariner

    Feb 18, 2005
    Front Royal, VA
    BHB, do you think that vibration could be causing the distortion and hum, like disrupting the ground, somehow?

    I don't really think it's a factor of it warming up, I just didn't know how else to explain it.

    The funny thing is that as soon as I lower the volume, it'll go back to normal for a little, I keep on playing, and then it comes back.

    I'll probably have to take it in.... :bawl:
     
  6. Selta

    Selta

    Feb 6, 2002
    Pacific Northwet
    Total fanboi of: Fractal Audio, AudiKinesis Cabs, Dingwall basses
    If it's just a loose ground, yeah, I guess as you can shake it loose/into place. It doesn't happen to have a tube pre or tube driven MOSFET, does it? If so, check the tube, it's prolly bad. If not, time to bust out the meter and start checking caps. Feel free to IM or PM me with any questions/concerns you work yourself into. If you're not comfy with opening amps and tooling around, then don't, and send it to a tech, or else you run the risk of breaking more things..:D

    Ray
     
  7. mariner

    mariner

    Feb 18, 2005
    Front Royal, VA
    I've had this thing apart many times in the past week, cleaning out the cobwebs and spraying contact cleaner in the pots. I had it repaired once, but I let a friend borrow it for awhile while he was gigging and who knows how he treated it.

    I was just testing it again and if I maintain a really low volume with little or no vibration I was good for about 20 minutes so it's not heat, as soon as I start gradually cranking it gets to a point where the vibration gets to it and it craps out. What's funny is how the tone fattens when it fails.

    I used to do panel wiring in a former life, so I'll ring it out and see what I come up with....
     
  8. Selta

    Selta

    Feb 6, 2002
    Pacific Northwet
    Total fanboi of: Fractal Audio, AudiKinesis Cabs, Dingwall basses
    As a quick test, set the amp somewhere where it wont vibrate (i.e. on a pillow on tob the cab or something) and then crank it. Or even set it on a pillow on the floor beside it. Or far away, and then see if it does it still. Does it happen more with different settings at all?

    Ray
     
  9. Selta

    Selta

    Feb 6, 2002
    Pacific Northwet
    Total fanboi of: Fractal Audio, AudiKinesis Cabs, Dingwall basses
    Also, spraying high speeds of compressed air isn't the best of ideas on an amp, especially if it's warm. You might've in-advertanly knocked a ground wire loose somewhere, or even a signal wire from a pot or something.

    Ray
     
  10. mariner

    mariner

    Feb 18, 2005
    Front Royal, VA
    It's got to be vibration....

    I set it on a folded up blanket and it still happened.

    If I leave all the EQ settings flat and play lightly, it never skips a beat. As soon as I start playing hard or if a bump up the mid-lows or increase the Post-Gain, the growl comes back. Seems to like to initiate around the 5th and 7th frets on the E, just the right frequency....

    Time to dig out the meter....

    Thanks for responding and offering input

    BTW, do you know any good 3rd party sites that maintain amp schematics? Peavey had an owner's manual online and that was about it.
     
  11. Selta

    Selta

    Feb 6, 2002
    Pacific Northwet
    Total fanboi of: Fractal Audio, AudiKinesis Cabs, Dingwall basses
  12. Passinwind

    Passinwind I Know Nothing Supporting Member

    Try plugging a different preamp directly into the power amp input (or EFX return, etc). If the problem goes away, you now know where to look next. If it doesn't, you still know where to look next... :cool:

    Luck,

    ============Charlie

    PS, for schematic links, try Ampage at www.firebottle.com .
     
  13. mariner

    mariner

    Feb 18, 2005
    Front Royal, VA
    I found that Peavey has a decent forum. I signed up there and noticed a few posts concerning Combo 300s. I tried all their suggestions to no avail, things like patching the effects loop and the Pwr Amp loop. I still had the same results. I always thought the speaker was sealed up in this amp, but apparently the front grill uses industrial strengh velcro. I'm going to check out the speaker condition and see what they tell me in response.

    I'll let everyone know what I find...
     
  14. mariner

    mariner

    Feb 18, 2005
    Front Royal, VA
    As it turns out, the issue was the speaker. I took the magnet off the basket and found a tar-like substance on the inner surface of the central cone. I scraped this off and it sounds great. Don't know if this a true fix or just a temporary improvement. At least I know what the problem was.

    Now, some shielding and re-wire of my pots and that annoying hum from turning up my tone knob on the bass should make everything good....

    Thanks.