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Hartke LH500 Broken Input--What's the Problem?

Discussion in 'Amps and Cabs [BG]' started by Alex Kitching, Dec 24, 2014.

  1. Dec 24, 2014 #1
    Alex Kitching

    Alex Kitching

    Dec 24, 2014
    I was playing a show last Friday night with my passive P Bass running into the passive input on my Hartke LH500 head, then into an Acoustic B410 cab. In the last song I heard a massive buzzing noise come from my amp. The sound cut out but then almost instantly came back. For the next few days the amp worked, but with a constant high-pitched squeal that worsened when I switched on the tweeter. Today I plugged in the head into the Acoustic B410 and there was almost no sound at all. Only a very quiet signal when the amp was cranked. I also plugged the head into my other cab (Avatar B410) and there was the same problem. I tried the active input on the head and it works just fine. What could my problem be and what would be the best way to fix it?
     
  2. Dec 24, 2014 #2
    BassmanPaul

    BassmanPaul Inactive

    Aug 25, 2007
    Scarborough Ontario Canada
    Did you try a new signal cable? Mine gave me some grief a couple of weeks back. Somewhat similar problem to yours. The metal of the plugs had corrosion on them and wouldn't switch the bass on consistently.

    If the amp has an effects loop try linking the send and return. Some times the sockets switch contacts can corrode even if you don't use them.
     
  3. Dec 24, 2014 #3
    FunkHead

    FunkHead Supporting Member

    Mar 10, 2007
    Pop the top off and look at the input jack. Maybe you can see the problem. Make sure it is unplugged while messing around in there.
     
  4. Dec 25, 2014 #4
    Munjibunga

    Munjibunga Retired Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    Also try cleaning the input jack with Caig DeoxIT or similar product.
     
  5. Dec 25, 2014 #5
    BassmanPaul

    BassmanPaul Inactive

    Aug 25, 2007
    Scarborough Ontario Canada
    I can't agree with this post unless the OP has some technical expertise. All of the folk who do tech work have seen examples of owners who have tried to "fix" their amplifiers. Usually these cost much more to repair.

    OP take your amp to a tech. It may be that the input socket ground solder joint has failed. If this is the case usually that joint just needs to be reflowed. That will cost little more than the bench fee unless the tech finds more problems.

    The amp is still fully functional if you use that active input. You may need to boost the volume a bit to compensate for the lower level the Active input provides.
     
  6. Dec 26, 2014 #6
    Alex Kitching

    Alex Kitching

    Dec 24, 2014
    Thanks everyone, this is is solved now. I don't have any technical experience, but my dad (electrical engineer) helped me pop the top off and fix things up. We found that a capacitor was blown AND some of the soldering between the input unit and the preamp board had come undone. It was a lot of work (these things are barely user serviceable) but we put in a new, better capacitor and soldered the input in place. Works just fine now. Also, we did some reinforcement soldering on quite a few connections that looked sketchy. Is this a typical experience with amps or is this a quality thing I should let get to me? I had an Acoustic B200H, also made in China, smashed it around with my band, had kids yank out the input, etc. and had zero problems.
     
    Last edited: Dec 26, 2014