Pictured is the power section of a midi controller mainboard. It's a PreSonus Atom SQ (The motherboard is labeled "BEEP_Main_Board_V3.0").

The sad story is that it was bought 2nd hand and unfortunately worked for a day. The sadder story is that it's probably my fault.

The device works with a USB 3 cable and not external power supply. I connected it to both my desktop and my laptop and it worked just great. I then wanted my daughter to disconnect from 'A' computer and connected the device to an iPAD via a lightning to USB cable designed for MIDI. Problem is (I guess) that the device drew more power then what the iPad can provide, and I needed to use the Apple lightning to USB3 adapter as it has an extra port for external power.

Long story short - the device will power on, but the screen flickers and no lights. Even more so, it will go into software update / recovery mode, with the screen fully functional and recognized by the computer, and finish a firmware update with no issue. I assume, the burnt-looking component is to blame (and me).

  • Any way to figure out what is the component value based on the circuitry around it?
  • I assume Q10 is the issue and should there be something in C76?

I have some basic understanding in electronics and got some equipment at home, like a multimeter and a very good soldering station, but reverse engineering a circute is above my abilities.

Also, contacted PreSonus and was not treated nicely as the device was bought 2nd hand and they will not support that. And the local distributor refused to fix this (very common in Israel) and said the company said that there are no more spare parts.

More hi-res images here

enter image description here

Detail of Q10

enter image description here

  • \$\begingroup\$ Welcome! Lift Q1 and measure source pad to ground resistance. \$\endgroup\$
    – winny
    Sep 28, 2023 at 18:33
  • \$\begingroup\$ So that's a USB power input and/or interface? Looks like a power enable for the rest of the circuit. Q10 might be a PMOS transistor. \$\endgroup\$ Sep 28, 2023 at 18:53
  • \$\begingroup\$ OK, so managed to read the writing on Q10 - It says "ADSL 19" Makes any sense? \$\endgroup\$
    – etgalim
    Sep 28, 2023 at 19:25
  • \$\begingroup\$ @TimWilliams It's both. Reading through the spec, it's a USB 2 bus \$\endgroup\$
    – etgalim
    Sep 28, 2023 at 19:26
  • 1
    \$\begingroup\$ @winny Thanks! I needed some Googling to understand what "Dead Short" is and why it's good that it's not the case. I'll definatly try to replace Q10 once I'll figure out what it is and source it. \$\endgroup\$
    – etgalim
    Sep 28, 2023 at 20:43

1 Answer 1


I think this could be a AO3413 P-FET.

The image markings documented here match exactly, including the two numbers at right angles. The idea of this being a PFET for high side switching, also fits the place on the PCB.

Here's an image of the part on Alibaba enter image description here It shows the fixed "AD", but obviously a different week and lot code.

  • 1
    \$\begingroup\$ ...a PFET for low-side switching? Why would you ever use a PFET for low-side switching? \$\endgroup\$
    – Hearth
    Sep 28, 2023 at 21:17
  • \$\begingroup\$ You are of course correct, I meant high side switching. I have corrected my answer! \$\endgroup\$
    – colintd
    Sep 28, 2023 at 21:21
  • \$\begingroup\$ Too many answers on NFETs, and a disengaged brain. \$\endgroup\$
    – colintd
    Sep 28, 2023 at 21:25
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    \$\begingroup\$ Thanks @colintd. I'll just have to take your word on this :) I'll try to source it locally to save time, but I'll also order a few, just in case. In the meantime, I removed the old one as suggested, and here's a photo of the inner side. (Not the greatest removal job, but it's what I have) photos.app.goo.gl/YN6yQxVVAZpjp64J7 \$\endgroup\$
    – etgalim
    Sep 28, 2023 at 21:52
  • \$\begingroup\$ What's your address? I'll ship flux and solder braid ;) \$\endgroup\$
    – MiNiMe
    Sep 28, 2023 at 23:24

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