Tweaker's Asylum

• You will need an electronc multimeter - Benoit 01:28:35 03/17/03 (0)
  In Reply to: How do I test DC leakage from my SS integrated amp? posted by FCS on March 14, 2003 at 15:21:45:

  and the cheapests are digital...
  You are looking for voltages in the range 10-500 mV (a thousand of a volt).
  Switch on the amp. Disconnect speakers. Switch on amp. Set meter on DCV range. Connect meter in speaker output (polarity don't matter).
  Read results (wait for amp to warm-up before final reading).
  A few hundreds millivolts is tolerable, more is not. If you can adjust, target should be less then 50mV.
  
  

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• Re: How do I test DC leakage from my SS integrated amp? - John Escallier 19:54:26 03/14/03 (0)
  In Reply to: How do I test DC leakage from my SS integrated amp? posted by FCS on March 14, 2003 at 15:21:45:

  I think the correct term you are looking for is DC offset. It is a DC voltage present at the output terminals..

  I recall from my tigersaurus days, looking for offset in the 5 to 10 mV range.. Preferrably, use an 8 -10 ohm dummy load for tests, as, if an offset is present, you'll damage more..For these tests, you do not need large resistors, 10 watts should do..One on each channel..if an offset oveheats those? Bingo, go no further.

  With the amp on, with no signal, with a dummy load, look at the output voltage in DCV, across the terminals used to connect the speaker wires to the amp. Start in the higher range, say 50 volts, then work the meter down the ranges until you get a reading .

  Then, with the various sources active, but no signal, select each source, looking for output offset as a result of a particular source. Sometimes, the amp is DC coupled, meaning an small input dc signal will make it to the speakers. Run the volume control up and down, watching the meter.

  Do not connect the meter to the output terminals while the meter is set to amps...This may burn the meter, or possibly damage the amp.

  The last option I can think of is perhaps the amp, after long use, drifts as a result of thermal issues..

  How do you know the coils were burned?..And burned by dc offset?

  Smell?, loosness of coil wires, just open circuit? Sometimes a coil autopsy reveals the failure mechanism..

  Cheers, John
  
  
  

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