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Do I have a defective AMP2 module?

joe jasniewski

June 27, 2020 20:23

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Recently took delivery of one of these amps, which I connected to my already working RPi 3B loaded with MoOde. I initially powered it using a 19.3V PSU, one that I've successfully used to power another TAS chip amp previously.

No +5V. The board says 18V at the input terminals. So I tried a 16V PSU, figuring OVP on the little on board converter. Get +5V this time, but not for long.

The only way it runs with the 16V PSU is if I co-power it using the ordinary pi 5V input. In this case, the AMP2 plays correctly. If I remove the additional 5V PSU connected to the pi, it drops out dead within a few seconds.

Do I have a defective AMP2 module?

HiFiBerry says it's supposed to power the pi and then some from the amplifier power input. I know the TAS amps are good for 24V and HiFiBerry only warns against using >18V with 4 ohm speakers... Implying it should work with, oh, 19.3V input and 8 Ohm speakers (which I have) no problemo.

I'm using the screw terminals, versus the quick connect for the PSU connection.

Any help would be appreciated. Thanks!

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4 comments

• 0
  
  HiFiBerry team June 27, 2020 20:54

  Unfortunately I can't say just from some symptoms. Only way to say for sure if there might be a hardware problem is to test the board here. I recommend to get in contact with the dealer you bought it from.

• 0
  
  joe jasniewski June 27, 2020 23:35

  Thanks for the quick reply.  I bought it from Chicago Electric, via Amazon.  Quick delivery.

  1. It's supposed to power the Pi when supplied with DC within the range of ??  (guessing anywhere 12 - 24V is all OK)

  2. It's supposed to be plug/play, yes?  No jumpers to set - just connect and works, correct?

  Looks like I'm in a streak of bad luck.  I've already emailed them on the issue.  They'll probably want me to return the defective unit first - for another two weeks without a playing system...  FWIW, this is what happens to someone when a well intended circuit fails, due to design / manufacturing issue.  AFAIK, I didnt do anything wrong connecting the two different PSUs. 

  Was hoping for something like the connector is for single PSU operation, screw terminals for separate Pi and AMP2 power.  Didnt get lucky there either -

   

  Thanks again,

   

  Joe

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  joe jasniewski June 27, 2020 23:50

  Update - looking at the components around the +5V converter control chip, C29 is damaged / missing.  Looks like it goes between pins 1 and 8.  May I have the value, please?  At least that will allow me to assess whether I want to attempt repair myself, or wait the time for a new board.

  I'm an EE with 30 years experience in computer power supply test. 

• 0
  
  joe jasniewski June 28, 2020 00:03

  It's 0.1 uf.  I fixed it using a leaded part across pins 1 and 8.  Playing music from the 16V PSU as I write this...