I recently got a new Raspberry Pi 3 Model B+ and I managed to flash the OS. But the problem seems to happen when I try to boot it. I do not have the official adapter, but I tried the following:

  1. with a USB to Micro USB Power supply by connecting the USB to my Mac.

  2. I had another power adapter that I was using on my mobile phones. It is rated at OUTOUT: 5V 1A

With both the options, I get a constant red light after a couple of seconds of connecting the Pi to the power source. Is this some problem with the Power source? How can I resolve this? I have tried to flash my card atleast 5 times, but to no success. I then came to the conclusion that this could be a problem with the Power source. Can anyone throw some suggestions on how I can make this work?

  • 5V at 1A is sufficient as long as there are no power-hungry USB devices. Perhaps not even a WiFi adapter. Certainly no Arduino expecting power. 2.5A would be better, in any case. I'm not sure what this question is asking. For instance, why is a couple of seconds distressing? Also, the crux: Does the thing boot? The more information you supply in your question, the better the answers it will attract. (from review)
    – SDsolar
    Commented Apr 21, 2018 at 0:01
  • You seem to think the red LED is a problem; this means voltage is OK. You CANNOT power a Pi from USB on a PC. Some just supply 5V, which should be limited to 500mA. The Mac will only supply 100mA unless a higher current is negotiated, which the Pi CANNOT. If the 1A PSU is an Apple it will run a Pi3 B+ (without peripherals).
    – Milliways
    Commented Apr 21, 2018 at 1:37
  • I'm not sure what this constant red light is about? Is it because of the Power Source? How can I verify what is going on in the Pi when I boot it up?
    – joesan
    Commented Apr 21, 2018 at 4:04

5 Answers 5


Seems there is no problem at all with your Raspberry Pi. A constant red light, the PWR led, indicates that your raspi is properly powered up. With a bad power supply it would flash below 4,63 V. So you do not have to worry about your power supply with 1 A output. It's enough in this case. For further information look What do system LEDs signify?. With a display and keyboard attached you should see that your raspi properly boots up.


As pointed out earlier the problem is not with the power supply. 1 A is enough to run a RPi.

Here are some ways to revive an RPi

Try the pin method

sometimes the SD-card reader on the pi gets deformed over time, so applying some pressure on the SD-card with a pin or folded paper could work, also cleaning it with a brush works sometimes. refer to this for further explanation

how a deformed SD-card looks

You could try booting from a USB

(assuming your USB ports are in a good shape)

Flash a USB disk or you can just insert your SD-card into a USB SD-card reader
Since you are using an RPi-3b+ you only need to write
In config.txt then try booting.

If it doesn't work (USB disk doesn't get powered) then measure the voltage between PP-2 and PP-27 or PP-7 and PP-27 ideally it should be around 5V if it isn't then you could connect PP-2 and PP-27 like this over here or you could replace C97 and U13 like done over here.


if USB does get powered but you can't boot then either

the Device is not supported or
the Device takes longer than 2 seconds to power up or respond.

Here are some supported USB Drives

  • Sandisk Cruzer Fit 16GB
  • Sandisk Cruzer Blade 16Gb
  • Samsung 32GB USB 3.0 drive
  • MeCo 16GB USB 3.0

If you are not using one of these, there is still a good chance that your USB drive is supported.

If all fails

If Nothing works then probably your RPi is RIP, if it is really dead then it will not read any 'Mass Storage Device' give any HDMI output, and have a cold Soc, some 5V GPIO sources may work, like for a fan.

If your pi isn't cold then there is some CPU activity but no storage to read so in this case you should replace the SD-card slot or USB slots however it's risky and might damage your pi, though it is worth a try since a working pi is better than a dead one.


You must remember that an RPi is a small computer the size of a credit card for $35 not some super-expensive gaming rig if it is dead then toss into a bin or replace it. Don't waste your time tinkering with an expensive red LED.

Hope this helps!


Buy a better power source. The recommendation is that a Raspberry Pi 3 B+ needs a power source rated for 5V at 2.5A so one that is only going to output 1A is definitely not enough. Standard USB ports only provide 500mA (USB 2) or 900mA (USB 3).

  • 5
    You DEFINITELY CAN run a Pi3B+ with a decent 1A supply - I do it regularly. Just don't expect to power any peripherals. Of course most PSU are NOT decent, and the cables are even worse. See Raspberry Pi Power Limitations
    – Milliways
    Commented Apr 21, 2018 at 1:41

Whoa, Whoa, Whoa!!! Dont give up just yet. I been where you been. Its a sad day when a raspberry pi die's. However I got good news for you. Speaking from personal experience. I have resurrected raspberry pi's from the dead. Yes the solid red light of Doom!!! of Doooom!!!. Promise me two things your gonna do before you place your raspberry pi in a shoebox and bury in the back yard. Yes Ive done this yes its sad. Ok down to business first.

  1. Try a new raspian image on a fresh new sd card.
  2. Buy the raspberry pi standard power cord on Amazon for $10. This is not the problem but it will cause problems down the road without the right power cord. FYI the low voltage message and lightning bolt will lead to madness.

" Do these two things my friend, before throwing in the towel and all hands are lost".. Note, make sure you download the official and current image from the raspberry pi website. Cloning a bad image from github will force you listen to very sad music. So try those two things and I promise you your Pi will be ok. Unless, shorted, microwaved, stepped on,act of cat or act of soda. Save a Pi, Save the World!!! and possible your sanity.


I had the same problem when I used my laptop as power source without a power source supplied to the laptop. As soon as I had my power attached to the laptop and rebooted the pi ungracefully everything worked like a charm. Regarding the power source I had the same problem when not using the official power source vs. the official one.

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