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SWR SM-500 Issue....

Discussion in 'Amps and Cabs [BG]' started by SurfLlama, Feb 21, 2006.


  1. SurfLlama

    SurfLlama

    Feb 21, 2006
    Santa Cruz, CA
    Hey Folks!

    I've been a lurker on TalkBass for a long time.. but have been content to just soak up the information, and haven't had anything new to share. Until now...

    I've been playing through a SWR SM-500 and an Eden D410XLT (8 ohm)(for about 6 years, gigging probably 3-4 times a month with this gear. A few months ago (around the same time that my band changed rehearsal spaces) I decided that I would like a more modular set up. (read.. I got tired of humping the 4x10 around.. and replacing the casters on it..) So.. I sold the 410.. and bought an Eden D210XLT (8 ohm) and a 2nd hand Eden D115 (also an 8 ohm cab).

    The amp is in bridged mode... and I run a speakon cable from the amp to the 210.. and a speakon to banana cable from the 210 to the 115. I'm not a super genius at the impedance stuff, but that should be 4 ohms.

    Now.. the issue. I keep blowing fuses! The fuse isn't the one that's accessible from the back of the amp. It's an internal fuse that goes between the AC plug and the AC fuse. I've replaced it a few times but, this is obviously not cool.. and I would like to find out what might be causing this.

    I know the amp is used to running an 8 ohm cab.. but it's still rated for 4 ohms.. so I'm not overdriving it. And my idea that maybe the original fuse was just a little old and burnt out was shot out the window when a new fuse burned up.

    Any idea what this might be? Could it be the wiring at the rehearsal studio? My rack set up has a furman power conditioner that the amp plugs into, and them the furman is plugged into a power strip (That only I am plugged into).

    Any advice would be really appreciated!

    Also, I have never replaced the pre-amp tube.. should that be something that I look into pretty soon?

    Thanks a ton!
    Matt
     
  2. Check your manual to make sure the amp can go to 4 ohms in bridged mode.

    In other words, the SM-900 can go to 2 ohms per channel, but only 4 in bridged mode.
     
  3. SurfLlama

    SurfLlama

    Feb 21, 2006
    Santa Cruz, CA
    Thanks for the idea.

    According to the manual, in bridged mode the SM-500 can put 500W into 4 Ohms..

    Thanks again!

    Matt
     
  4. tornadobass

    tornadobass Supporting Member

    Nov 20, 2000
    Iowa City, Iowa
    Endorsing Artist: Black Diamond & SuperSensitive strings
    The amp should handle 4 ohms bridged, although it will run hotter there. That would cause thermal shutdown but not a blown fuse.

    Check your speaker cables for possible short, but even then, it would cause heat or a blown speaker fuse...are those on the back for your amp?

    About the tube, it's something to check, it's unlikely to be the problem.

    Might be time to take the amp to a tech.
     
  5. pickles

    pickles Supporting Member

    Mar 23, 2000
    Ventura, CA
    Yikes, thats too bad. I blew a fuse once in an SM-400S, I seem to recall their tech suggesting I go with a slightly higher value fuse :eek: I DONT recomend that unless SWR themselves tell you to and stand behind it. Is the box still under warantee? It should have no trouble bridging into 4 ohms.

    One suggestion, open up both boxes and make sure the speakers themselves have the stated impedence ratings. If somebody replaced the 8 ohm driver in the 115 with a 4 ohm driver, you could be running 2.6 ohms, which might cause it to draw excess current and pop the fuse.

    How great does that 115T sound? I love that cab.
     
  6. SurfLlama

    SurfLlama

    Feb 21, 2006
    Santa Cruz, CA
    I swapped cables to check that... and the speaker fuses are fine.

    I'm thinking the same thing about a tech... this stinks.. I can't really be without a head for too long.
     
  7. SurfLlama

    SurfLlama

    Feb 21, 2006
    Santa Cruz, CA

    Unfortunately, it's not under warranty... it's 6 years old. (just missed it!) I did open up the box on the 115 to make sure the Eden driver hadn't been replaced with a cheap replacement. Sure enough the driver is an 8 Ohm driver.

    I'm thinking I should pop open the 210XLT and double check that as well, I know it's a long shot but these things do happen.

    The 115 is a great cab... I don't use it for every show, but it's a fantastic addition to the 210xlt for big rooms.

    M
     
  8. tornadobass

    tornadobass Supporting Member

    Nov 20, 2000
    Iowa City, Iowa
    Endorsing Artist: Black Diamond & SuperSensitive strings
    I've been using an Eden D115-T for smaller/medium gigs and it does nicely...actually better than my Goliath II for focus and clarity.

    For bigger places, I add in the Eden D210-T, which actually weighs more than the 15 cab.
     
  9. pickles

    pickles Supporting Member

    Mar 23, 2000
    Ventura, CA
    Those -T cabs sound amazing together. I have high volume requirements, so I use the same rig in the XLT versions ... but the Ts actually have better tone IMO.
     
  10. I had the exact same problem with my SM-900. Running a 4 ohm cab in bridged mode. It blew the output fuse, at least on the 900 the fuse is located on the outside. It also went into thermal shutdown.

    The last thing you can try is blowing a fan into the rack to keep fresh air cirulating into the rack and into the amp. If that fixes your problem, mount a fan onto your rack.

    This is my post from this thread.
     
  11. slugworth

    slugworth Banned

    Jun 12, 2003
    So. Calif.
    >>>> you might want to check your speaker impedance with a meter, as it could have been mislabled. That way you don't have to open up the cabinet. I use a 115T with my SM500 for smaller gigs, but I have a 4 ohm JBL 2226 installed. The SM500 can easily blow or overexcurt the 200W Eden speaker. Plus the SM500 runs HOT!!!! Make sure there is an empty rack space above and below to help with air flow and cooling. An auxiliary computer type fan isn't a bad idea.

    Slug
     
  12. SurfLlama

    SurfLlama

    Feb 21, 2006
    Santa Cruz, CA
    I might have to give that a shot... still the 210XLT is a Nice all around package too!
     
  13. SurfLlama

    SurfLlama

    Feb 21, 2006
    Santa Cruz, CA
    Okay.. silly questions time.. how do I check the impedance? I have a meter (not an expensive one, but a decent one I got as a gift and have really only used to check continuity.)

    I'm not that heavy on the volume, and I never overdrive anything. That's what makes this so frustrating, I don't abuse my gear!

    Thanks for the help!

    Matt
     
  14. SurfLlama

    SurfLlama

    Feb 21, 2006
    Santa Cruz, CA
    Hi Golden Boy,

    It's not the output fuse (or what SWR calls the main fuse) at least, which is accessible from the outside via a fuse holder on the SM-500 (takes a 7amp sloblo) it's an fuse that it hard wired (a fuse with leads) between the AC plug, and the main fuse holder.

    The fuse in question.. as indicated by my lovely red arrow...

    [​IMG]

    The 2nd time it happened I wired in a fuse holder that is accessible from the outside, just so I wouldn't have to pull it all apart if it all happens again.

    The muy frustrado part of all of this is worked like CHAMP for over 6 years.. and now it's f'n up. I'm so fed up, I'm thinking of canning it and dropping the dough on an Eden...

    Thanks for your help!

    Matt
     
  15. pickles

    pickles Supporting Member

    Mar 23, 2000
    Ventura, CA
    You can meadsure DC resistance, but thats not the same thing as AC impedence (which is what matters). Best bet is to just take out the speakers and look at them.
     
  16. jz0h4d

    jz0h4d

    Apr 26, 2005
    Part of the problem with these SWR amps is that the air flow over the output transistors exits the amp on the left side. When you put these wide amps in a rack case the air flow is impeded by the side of the case. I put mine in an SKB plastic case and drilled a bunch of holes in the side of the case for the hot air to exit the case.
     
  17. SurfLlama

    SurfLlama

    Feb 21, 2006
    Santa Cruz, CA
    Yeah, I'm thinking about adding some compuer case fans to the rack.

    I have a 6 space rack.. and it's full of stuff with the conditioner/tuner the amp and a drawer. So I'm sure there's not a lot of airflow.

    I played through just the 210xlt last night.. and the fan kicked on WAY before it used to when I ran the 410xlt. I'm gonna crack open the 210XLT tonight after work...

    M