DSL 401 troubleshooting help

Discussion in 'The Workbench' started by Holt2010, Oct 23, 2020.

  1. Holt2010

    Holt2010 New Member

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    Hey guys I need a little help troubleshooting my DSL 401. The amp powers on but I have no output.The tubes are also not lighting up. All the fuses check good with a multimeter including the internal one. I’ve checked voltages at all the tube sockets and seem to have the correct voltages. However I don’t have any voltage at the bias test points. This amp also has had the bridge rectifier replaced and a heat sink added. Any help would be much appreciated .
     
  2. Chris-in-LA

    Chris-in-LA Well-Known Member

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    Don’t know your amp model but it sounds like you don’t have voltage to the heaters if the tubes are not lighting up. Check again. Most preamp tubes have 3.5 volts AC at pins 4,5 and 9 with negative probe grounded to the chassis. Power tube heaters are pins 2 and 7.
     
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  3. KraftyBob

    KraftyBob Well-Known Member

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    No voltage to the heaters is your power transformer, or the wires coming off that tap.

    Be careful when inside a powered amps. Lots of lethal voltage in there.
     
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  4. Jon Snell

    Jon Snell New Member

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    The common issue is the T6.3A fuse goes open or gets so hot it gets a bad connection.
    Designated F4.
     
  5. tmingle

    tmingle Well-Known Member

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    Its probably some bad solder joints. THESE AMPS ARE NOTORIOUS FOR THIS VERY ISSUE!!! I had 1 & re-soldered the board 3-4 times in the 15 years I owned it.
    BE CAREFUL!!! EVEN WHEN UNPLUGGED, THE CAPS RETAIN SOME PRETTY HIGH SHOCK POTENTIAL.
     
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