Psst... Ready to join TalkBass and start posting, make new friends, sell your gear, and more?  Register your free account in 30 seconds.

swr900 loud hum frequency problem

Discussion in 'Amps and Cabs [BG]' started by raindog1234, Sep 11, 2005.


  1. raindog1234

    raindog1234

    Sep 11, 2005
    Hello,

    Recently ive been having this problem where there is this very loud high pitched hum coming from my amp head inside the case it seems. its kind of like when a kid with braces gets up close to a computer and that hum starts. dosn't seem to be coming from my speaker cab at all. Only way to make it stop is to tap or hit it on the top. Never usually happens right away but all of a sudden it will start happening. Sometimes right when i turn it on and sometimes not till ive had it on for awhile. I mostly use a roscoe 5 string active bass. When a friend of mine borrowed my amp he said his passive bass would get a crackling high pitched metallic sound coming through the speaker along with the loud frequency hum when turned up to loud volumes. Any help would be greatly apreciated.

    Thanks,

    Rich
     
  2. mettec

    mettec

    Aug 22, 2005
    Minneapolis
    I have a SM-900 as well. It sounds like you have a loose ground wire inside. First check the ground lift switch on the back if you hear a big difference but still makes some noise then that would be your problem. If it dosn't make a difference then the input jack might have a wire loose(meaning might be unsodered ). Plug into both input jacks and see if there is a difference as well. Had same problem and that took care of it. Let me know if this helps.
     
  3. raindog1234

    raindog1234

    Sep 11, 2005
    thanks for the reply. I made my post before I plugged it in for the first time in about 3 months. I had to put it in storage before I moved away for the summer. That was the problem i was having before. I took it out of storage today and set it up and now there is pretty bad distortion coming from the cab when i hooked it up with an active bass I own and that hum is still there. Then i hooked up a passive bass and there was less distortion but that mettalic ringing sound was there. I tried the things you said to do and none of them seemed to make any improvements. I thought maybe it was my cab so i hooked up another head and ran my cab through a combo amp i have and it seemed to be working fine no distortion or ringing sound. I did have some screws that seemed to have come lose and were rattling around inside the head. I opened it up and took them out. That was the only thing that was unusual. hope its not anything too serious.
     
  4. andysvec

    andysvec Supporting Member

    Aug 15, 2004
    Guam
    I have an sm900 that I bought new about 10 years ago and experienced something similar recently. There was a noise coming from inside the unit and not through the speakers. I found out that my noise is actually the cooling fan inside, I read somewhere else about this also and it is the bearings in the fan going bad. I need to find a replacement fan myself, I haven't started looking yet but will probably write swr one of these days as a start.
     
  5. mettec

    mettec

    Aug 22, 2005
    Minneapolis

    Ok, then the only thing that I think it might be is that you have a bad tranformer in the amp. Call Fender/SWR Division and they might be able to help you. Do you know of a Authorized Repair Center in your area? SWR would have that or they will have you ship it to them. They are pretty good guys at SWR ( Not Fender Reps they kind of suck ) Keep me posted.