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Amp2 Not Working With 18V Power Supply in Headless Mode

Simon

February 20, 2021 14:27

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Hi all,

I bought the Amp2 last week and got it setup this week with my Raspberry Pi 3B+ and the latest Hifiberry OS. However, the 18v / 3.3A power supply doesn’t power up the device so that it’s visible on my network. A single Raspberry Pi LED comes on, but no LEDs light up on the Amp2 board, and the device isn’t visible from my iPad.

I finally got it to work by connecting a 7” Rpi screen which required using the Rpi 5V PS, and now I can see “Hifiberry” on the network, I can view the Hifiberry OS on-screen, and can stream from my iPad to the Rpi/ Amp2 no problem.

But in headless mode I.e. no screen connected, using only the 18v PS, I cannot get the Amp2 / Rpi to show up on the network even though the Rpi LED comes on. It’s as if there isn’t sufficient power getting to the Amp2/ Rpi.

Any suggestions to get it working with the single 18v PS?

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21 comments

• 0
  
  HiFiBerry team February 20, 2021 17:04

  I don't think this is a power issue, as there is no more power needed without a screen. However, I also have no idea what might be causing this.

• 0
  
  Simon February 20, 2021 19:56

  Hmmm... that would mean then that either the power supply or Amp2 are faulty. I’ve eliminated the possibility  that the Rpi is a problem: I tried another 3B+ and got the same results.

• 0
  
  HiFiBerry team February 20, 2021 20:40

  Could be some software bug. But without a screen connected there's no way to debug it.

• 0
  
  Simon February 20, 2021 21:50

  I have 7” Rpi screen as mentioned, and of course it requires the Rpi PS to run, but when I do this, the Hifiberry OS appears and seems to work no problem.  There’s music coming from the 4ohm speakers, but maybe it’s not boosted by the Amp2, just passing through it from the Rpi?
  I noticed in headless mode just now that there’s no lit LEDs. Again it makes me think there’s no power getting to the Rpi. Yet I can hear a very faint high pitched sound if I put my ear to the Amp2 board.

  I’ll try loading another streaming OS and see what happens.
  
  

   

• 0
  
  Simon February 21, 2021 03:41

  I tried Volumio and it seems there’s a voltage issue: https://imgur.com/a/P4rToHO

  I tested it in two different outlets and got the same result.

   

• 0
  
  Simon February 21, 2021 16:46

  Here’s a short video of the Amp2 getting plugged in to the 18v PS. Note that no LEDs light up. Volumio was used for the OS but Hifiberry OS has the same result, ie. it isn’t visible on the network, so doesn’t appear to be booting up. 
  If I remove the Amp2 and boot the Rpi with it’s 5v PS, the Rpi lights up, and is visible on the network, so no problem there.

  At this point it looks like there’s a Amp2 board issue.

  Edited by Simon February 21, 2021 16:49
• 0
  
  HiFiBerry team February 22, 2021 09:46

  While it might be a hardware problem, this wouldn't explain why it works with a screen connected. Did you buy this Amp2 directly from us?

• 0
  
  Norbert February 22, 2021 12:01

  BTW it is better to have the spacer rollers (if you only use 2) on the other side than on the side of the GPIO bar.
  On the video it looks like the AMP2 is crooked.

  - Is it correct that the AMP2 can play LOUD (!) with the display?

  If so, it sounds like you have a problem with an interrupted ground line (power -). When you connect the display, it re-establishes the interrupted connection.

• 0
  
  Simon February 22, 2021 12:55

  Hifiberry team: No, I bought it through Buyapi.ca.

  Norbert: True, I’ve been meaning to swap the spacer locations or add the other 2 back. I’ll do that today
  With the screen attached, the speakers can play pretty loud — though I haven’t cranked it to full volume. I’m not sure what loudness would qualify as LOUD, however, LOL. I’ll compare it to the un-amped Rpi.

• 0
  
  HiFiBerry team February 22, 2021 15:03

  @Simon: Nobert might be right about the ground connection. You might check your power supply with a multimeter.

   

• 0
  
  Simon February 22, 2021 19:35

  With my multimeter, I measured 18.37v at the power supply, so it would appear to be ok.

• 0
  
  Simon February 23, 2021 03:53

  Another short video showing the PS voltage reading. Plugging it into the Amp2 doesn’t boot the Rpi. 
  Does this mean the issue is with the Amp2?

  Edited by Simon February 23, 2021 03:55
• 0
  
  Norbert February 23, 2021 09:05

  You can do a test with the multimeter.
  
  Remove the power plug from the AMP2 (at point 1 in the picture).
  Find the external contact (power -) of the plug inside the socket of the AMP2
  Measure the resistance (range 200 Ohm) individually between
  1 - 2
  1 - 3
  2 - 3
  The resistance should in any case be around 0 (zero) ohms.

   

  
• 0
  
  Simon February 23, 2021 14:14

  Thanks Norbert, I get:

  1-2: 0.00

  1-3: -30.2 (only get a reading if (+) probe is on 1, (-) on 3)

  2-3: -30.2 (only get a reading if (+) probe is on 2, (-) on 3)

   

   

• 0
  
  Norbert February 23, 2021 16:12

  I also tested this with my AMP2 to be sure and have measured 0 ohms between 1 - 2, 1 - 3 and 2 - 3.
  What I don't understand is that you measured - values (-30.2). Resistance measurement has no + or -
  
  Anyway, I think the problem is the AMP2.

• 0
  
  Simon February 23, 2021 19:04

  Hi Norbert, I’ve retested the resistance (see video) and get:

  1-2: 0.00

  1-3: 3.3

  2-3: 3.3

• 0
  
  Norbert February 23, 2021 20:18

  Hi Simon,

  1st. Your are in the wrong range! NOT 200kOhm (as in the video) but 200 Ohms, means 1st.  position from the resistance settings

  2nd. You are measuring at the wrong pin. NOT the 1st one, but the 3rd one on the left side.

• 0
  
  Simon February 24, 2021 00:36

  Hi Norbert,

  My bad, re: settings. But I found your diagram a bit vague re: pin 3.

  However, in remeasuring I get the following:

  1-2: 0.00

  1-3: 0.00

  2-3: 0.00

  So, if the results are the same as yours, but your Amp2 works, what else can the issue be?

   

• 0
  
  Simon February 24, 2021 15:42

  Hifiberry team, do you have any other suggestions as to why the Rpi and Amp2 don’t boot up? Any other tests to try?

• 0
  
  HiFiBerry team February 24, 2021 15:43

  No, unfortunately I can't say. I think, it's best to try another Amp

• 0
  
  Simon February 25, 2021 03:21

  Ok, thanks to you and Norbert for the other suggestions anyway.