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Class D Switching Power Amplifiers and Power D/A conversion

41hz Amp5 no sound
41hz Amp5 no sound
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Old 25th November 2012, 01:20 PM   #1
KrakBoem is offline KrakBoem  Netherlands
diyAudio Member
Join Date: Oct 2010
Default 41hz Amp5 no sound

I need some help with an Amp 5 of 41hz. I cannot post on their forum. Requested authorisation a number of times, but no luck.

The relay unmutes, but there is no sound. I measured the following
  • voltage on both rails (on the large capacitor) : 25,2v
  • DC voltage input cap (C150 ) to the +5V regulator : 21.9v
  • feedback: REF voltage (R42) : 1.2v
  • Voltage sensing first resistor R155 : 5.09v
  • relay coil voltage : 25.4v
  • The VN10 (charge pump, C34) should be 10V above the negative rail voltage: -14v /-25v
  • not sure if this is ok. 10v above negative rail = -14v
  • +2.5v on the chip side of both input caps to ground (Input caps are C35 & C36)
  • measured ~2.4v on the input
  • speaker out: no sound

During troubleshooting I shorted the mute / unmute wires and saw smoke coming from the side of the pcb with the input caps (or the input cap to the +5V regulator, or resistor for Current limiting for +5V or diode for +5V reverse discharge protection and the 5v regulator). I changed the input caps, but no luck.

I donít know how to troubleshoot from here. I assume that I should be able to measure a AC voltage after the input caps when there is an input signal?

Continuity from the RCA input to input caps is ok.
I donít understand the schematics well enough to check continuity for the whole circuit.
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Old 25th November 2012, 01:27 PM   #2
Tekko is offline Tekko
Join Date: Jan 2005
Most likely you toasted the audio inputs when shorting the mute/unmute wires.

These tripath amps seem to die for literally nothing, simply driving the input stage to clipping seem to be enuf to fry it, or simply even powering the amp on while given an audio signal.
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Old 25th November 2012, 02:10 PM   #3
KrakBoem is offline KrakBoem  Netherlands
diyAudio Member
Join Date: Oct 2010
"audio input", which items on the pcb would that be?
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