Repair Help - Problem with Trace Elliot V-Type

Discussion in 'Amps [BG]' started by TMacATK, Nov 13, 2012.


  1. TMacATK

    TMacATK

    Joined:
    Jul 9, 2008
    Location:
    Davis, CA
    I need a little help and advice diagnosing a problem with my Trace Elliot V-Type Combo. The amp is a 15" combo with a tube preamp (the same "V-Type" preamp you see in rackmount form from time to time) and a solid state power amp. Weirdly enough, it's not all tube but it does have a standby switch.

    The other day I went to noodle a bit and when I turned my amp on, there was immediately a super loud hum around the pitch of a "B" one octave below middle C. I knew something was wrong because the amp usually makes no sound (except for the sound of the fan) in standby. The hum continues no matter what, and turning up the volume increases the loudness of the hum slightly.

    I plugged my bass in to troubleshoot a bit and the amp still amplifies the bass, but crackles quite a bit. The gain, volume, tone controls and all switches still work. The passive and active input exhibit the same behavior.

    I thought it might have just been a bad tube, so I got an extra ECC 83 to troubleshoot and swapped out each tube (2 total) individually to try it out. No difference. I'm a little dismayed because I really hoped that the tubes were the problem - those are pretty easy to fix.

    I'm not an expert on the inner workings of the amp portion, but none of the electronic components are obviously externally damaged or loose. Everything on the inside is tidy. Also, I checked the fuse and it is not blown.

    I have tried different quarter inch cables, different power cables, different outlets, different speaker cabinets. I know it's not related to an external cable because the amp makes the sound as soon as it's powered up before anything is plugged into it.

    What do you think is wrong with my amp? I really appreciate your help because I'm not technically gifted in this area, and I don't have any amp repair places that I'm familiar with/trust. I don't want to pour a ton of money into diagnosing the problem only to find out it can't really be fixed. I love this amp and just want to get it back to working condition. Thanks!
  2. Bassmec

    Bassmec

    Joined:
    May 9, 2008
    Location:
    Ipswich UK
    Disclosures:
    Proprietor Springvale Studios
    It might be the pre amp or the power amp, so we need to audition the pre amp separately.
    So use another amplifier to test the pre amp,
    pull the loudspeaker jack out of the amps output socket to avoid hearing the noise via the speaker and then use the send socket to see if that is hum free.
    If it isn't then we need to consider two possibilities, firstly a failure of the power supply electrolytic smoothing caps, which I would change out any way due to their age as they really don't tend to last as well as most other components.
    But I think it's more likely, due to the crackling you describe that one of the power amp transistors and or its driver transistor has failed.
    Sometimes this is caused by the bias components of the amp drifting
    over time.
    Any music shop amp repair tech should be able to fix this no problem as its made out of easily sourced, common parts to almost all amps of this type.
    Finding an amp repair tech is all about asking your local PA hire company rather than a music shop what they would do.
    A music shop will simply try to make you buy a new combo and may offer you something for your broken one in part ex but I doubt it would
    be much.
    Sorry for your loss, it's a bit like having an old friend die isn't it.:bassist:
  3. TMacATK

    TMacATK

    Joined:
    Jul 9, 2008
    Location:
    Davis, CA
    Thanks for the condolences! The preamp is fully functional. The problem must be with the power amp.
  4. Mr. Foxen

    Mr. Foxen

    Joined:
    Jul 24, 2009
    Location:
    Bristol, UK
    Disclosures:
    Amp tinkerer at Ampstack
    I'd start by checking all the solder joints, and reflowing them, sounds like a gappy one from the crackling when you play.
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  6. MAMMOTHvolume

    MAMMOTHvolume

    Joined:
    Apr 29, 2009
    Location:
    sheffield, uk
    check the output for dc.
  7. Bassmec

    Bassmec

    Joined:
    May 9, 2008
    Location:
    Ipswich UK
    Disclosures:
    Proprietor Springvale Studios
    Yup if its pulling the speaker cone one way or the other and holding it there while making this heavy 120 Hz hum and cracking a bit.
    It's an output transistor gone to rail and it will destroy the speaker fairly quick if you run like that at all.:bassist:
  8. BassmanPaul

    BassmanPaul Gold Supporting Member

    Joined:
    Aug 25, 2007
    Location:
    Toronto Ontario Canada
    Tech time I would say. British Audio Service are the go to folk for all things Trace in the Americas.
  9. TMacATK

    TMacATK

    Joined:
    Jul 9, 2008
    Location:
    Davis, CA
    Can anybody explain how to "check the output for dc"? I don't know much, technically, about amplifiers.

    At this point, it sounds like my best option is to take the amp to a local amp repair shop or, as suggested above, to a specialist like the British Audio Service. Shipping probably wouldn't be too bad out to Tennessee for just the head.
  10. BassmanPaul

    BassmanPaul Gold Supporting Member

    Joined:
    Aug 25, 2007
    Location:
    Toronto Ontario Canada
    Turn the amp on without a cabinet connected. Apply a multimeter set to DC volts across the tip and sleeve of the speaker cable. You should read pretty much zero volts. You should start at the highest voltage range on the meter and drop down the ranges to the lowest. Up to about 100mV is considered acceptable but less is better.

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