Pi doesn't boot correctly

[jvm3]

Hey guys,

We (my brother and I) got ourselves a Raspberry Pi model B and it isn't booting correctly. We connected it to a TV, using a samsung phone adapter as a power supply. The splash screen always shows up, but after some time the TV says there is no signal and then the Pi reboots and the splash screen shows up again. In some cases, the Pi gets further and starts installing, but eventually it will reboot each time.

After some reading on the internet we found out that the problem was probably the power supply. So we measured the voltage on the testing points and while the Pi was active, the voltage was around 4.6 V, a bit low. We then used some different phone adapters and some usb power adapters with some usb to micro usb cables. All these power supplies supplied 5 V and at least 700 mA, but we also tried one with 2A. They all had the same problem.

We are therefore not so sure that the power supply is the problem, but we have no clue what else could be the problem.

Regards

[FTrevorGowen]

Hey guys,
We (my brother and I) got ourselves a Raspberry Pi model B and it isn't booting correctly. We connected it to a TV, using a samsung phone adapter as a power supply. The splash screen always shows up, but after some time the TV says there is no signal and then the Pi reboots and the splash screen shows up again. In some cases, the Pi gets further and starts installing, but eventually it will reboot each time.
After some reading on the internet we found out that the problem was probably the power supply. So we measured the voltage on the testing points and while the Pi was active, the voltage was around 4.6 V, a bit low. We then used some different phone adapters and some usb power adapters with some usb to micro usb cables. All these power supplies supplied 5 V and at least 700 mA, but we also tried one with 2A. They all had the same problem.
We are therefore not so sure that the power supply is the problem, but we have no clue what else could be the problem.
Regards

Even with a "good" "5V 1A" power supply a poor quality connecting cable can have enough resistance to lead to too much "voltage droop" at the Pi.
Some details (model type, spec. weblink) of the PSU's you've tried would be helpful.
FWIW (and esp. if you're "UK-based") my measurements of a number of PSU's and cables can be found at:
http://www.cpmspectrepi.webspace.virgin ... plies.html ,
http://www.cpmspectrepi.webspace.virgin ... dPSUs.html , and
http://www.cpmspectrepi.webspace.virgin ... esChk.html
Trev.

[jvm3]

Hey guys,
We (my brother and I) got ourselves a Raspberry Pi model B and it isn't booting correctly. We connected it to a TV, using a samsung phone adapter as a power supply. The splash screen always shows up, but after some time the TV says there is no signal and then the Pi reboots and the splash screen shows up again. In some cases, the Pi gets further and starts installing, but eventually it will reboot each time.
After some reading on the internet we found out that the problem was probably the power supply. So we measured the voltage on the testing points and while the Pi was active, the voltage was around 4.6 V, a bit low. We then used some different phone adapters and some usb power adapters with some usb to micro usb cables. All these power supplies supplied 5 V and at least 700 mA, but we also tried one with 2A. They all had the same problem.
We are therefore not so sure that the power supply is the problem, but we have no clue what else could be the problem.
Regards

Even with a "good" "5V 1A" power supply a poor quality connecting cable can have enough resistance to lead to too much "voltage droop" at the Pi.
Some details (model type, spec. weblink) of the PSU's you've tried would be helpful.
FWIW (and esp. if you're "UK-based") my measurements of a number of PSU's and cables can be found at:
http://www.cpmspectrepi.webspace.virgin ... plies.html ,
http://www.cpmspectrepi.webspace.virgin ... dPSUs.html , and
http://www.cpmspectrepi.webspace.virgin ... esChk.html
Trev.

Thanks for the reply.

We used three samsung phone adapters, all of them are have the model number ETAOU10EBE
The USB power adapter which gave the best result was the adapter of our samsung tablet. It is a 5V, 2A adapter with model number ETA-P11JBE (I assume this is the standard tablet adapter)

To connect this USB power supply to the Raspberry Pi, we used a samsung ECC1DU0BBK cable. This cable is about 0.8 meters long.

We thought the 2A should be enough, but apparently it isn't.

[GTR2Fan]

We thought the 2A should be enough, but apparently it isn't.

Anything from 1A upwards is plenty if it's genuinely outputting 5V under load.

[jvm3]

We thought the 2A should be enough, but apparently it isn't.

Anything from 1A upwards is plenty if it's genuinely outputting 5V under load.

So probably the voltage isn't enough. We have had the tablet for a bit more than a year. Could it be that the adapter is no longer able to ouput 5V?

[FTrevorGowen]

We thought the 2A should be enough, but apparently it isn't.

Anything from 1A upwards is plenty if it's genuinely outputting 5V under load.

So probably the voltage isn't enough. We have had the tablet for a bit more than a year. Could it be that the adapter is no longer able to ouput 5V?

It's not that it's "no longer able to output 5V" but it may be designed to be a "charger" rather than a "true" PSU. Most batteries like/expect/require much less than 5V when they're "empty" and thus draw a higher (charging) current. This is to ensure that they don't overheat. For laptops and netbooks this requirement is met via the control circuitry embedded in the battery pack so their power supplies will provide a more stable voltage w.r.t. to "load" (current drawn). This is not necessarily true of other "mobile devices" and so a PSU/charger may well be able to supply 5V at low currents but (deliberately) at it's maximum specified current the voltage may be only be ~4V (or less). An example of this is the Samsung TC E250:
http://www.cpmspectrepi.webspace.virgin ... ng_TC_E250
Referring back to your O.P. - what USB devices did you have plugged into the Pi? Were any of them "wireless"?
Trev.

[jvm3]

It's not that it's "no longer able to output 5V" but it may be designed to be a "charger" rather than a "true" PSU. Most batteries like/expect/require much less than 5V when they're "empty" and thus draw a higher (charging) current. This is to ensure that they don't overheat. For laptops and netbooks this requirement is met via the control circuitry embedded in the battery pack so their power supplies will provide a more stable voltage w.r.t. to "load" (current drawn). This is not necessarily true of other "mobile devices" and so a PSU/charger may well be able to supply 5V at low currents but (deliberately) at it's maximum specified current the voltage may be only be ~4V (or less). An example of this is the Samsung TC E250:
http://www.cpmspectrepi.webspace.virgin ... ng_TC_E250
Referring back to your O.P. - what USB devices did you have plugged into the Pi? Were any of them "wireless"?
Trev.

There were no USB devices plugged in. We only used the power supply, the SD card, a HDMI cable and an ethernet cable.

To clarify the problem a bit more: when the Pi is booting, we measured a voltage around the 4.75 V limit. In the course of time, the voltage drops slowly to about 4.60 V. At this point, the voltage drops rapidly and the Pi will shutdown soon after this. This whole process takes place in about a minute.

[default_user8]

If your TV has a USB port try that instead of your power supply(not the service port). Or get a powered USB hub off the verified device list here:
http://elinux.org/RPi_VerifiedPeripherals

[jvm3]

If your TV has a USB port try that instead of your power supply(not the service port). Or get a powered USB hub off the verified device list here:
http://elinux.org/RPi_VerifiedPeripherals

We tried to power the Pi using my laptop. We did this using two different USB to micro-USB cables. Both of them had the same problem again. With the first cable, the voltage started at 4.2V, the second one started at 4.0V. Both times, the voltage dropped slowly and the Pi shut down after a while. Although the starting voltage was significantly lower than 4.75V in these cases, it took longer before the Pi shut down.

Since we have tried a number of different power supplies, could it be that the Pi is the problem?

[FTrevorGowen]

There were no USB devices plugged in. We only used the power supply, the SD card, a HDMI cable and an ethernet cable.
To clarify the problem a bit more: when the Pi is booting, we measured a voltage around the 4.75 V limit. In the course of time, the voltage drops slowly to about 4.60 V. At this point, the voltage drops rapidly and the Pi will shutdown soon after this. This whole process takes place in about a minute.

That is very unusual behaviour. Since a Pi can boot "totally headless" can you observe the led behaviour and measure the testpoint voltage with only the SD card plugged in and then together with either HDMI or ethernet (but not both). Also check if any component "feels hot" and then report back what happened. Oh, and just confirm that you're not using an unpowered HDMI-to-VGA converter.
Trev.

[jvm3]

There were no USB devices plugged in. We only used the power supply, the SD card, a HDMI cable and an ethernet cable.
To clarify the problem a bit more: when the Pi is booting, we measured a voltage around the 4.75 V limit. In the course of time, the voltage drops slowly to about 4.60 V. At this point, the voltage drops rapidly and the Pi will shutdown soon after this. This whole process takes place in about a minute.

That is very unusual behaviour. Since a Pi can boot "totally headless" can you observe the led behaviour and measure the testpoint voltage with only the SD card plugged in and then together with either HDMI or ethernet (but not both). Also check if any component "feels hot" and then report back what happened. Oh, and just confirm that you're not using an unpowered HDMI-to-VGA converter.
Trev.

We now used a laptop as a power supply.
We tried to boot without HDMI and ethernet, the voltage then starts at 4.9V, then drops to 4.0. It then stays around 4.0 because it needs an internet connection to continue the installation.
The same thing happened with only the HDMI cable.
With only the ethernet cable, quickly after the boot, the voltage was again 4.0V. It dropped slowly to about 3.8V and stayed at this voltage. Up to this point, all the led had been burning. After a while, only the red led was burning. To see were it was stuck, we inserted the HDMI cable. But after this, there was no signal on the TV. The voltage was at 3.5V after inserting the HDMI.

With all the tests, the part between the SD card and the power supply got really hot. There even seemed to be a faint burning smell.

We did not use a HDMI-to-VGA converter, only a cable with two HDMI connections.

[mahjongg]

sounds like you have a triggered polyfuse that has been given no chance to recover, feel if it gets hot (F1 on the underside of the board near the power input) be careful not to get burned.

[FTrevorGowen]

sounds like you have a triggered polyfuse that has been given no chance to recover, feel if it gets hot (F1 on the underside of the board near the power input) be careful not to get burned.

+1
I was coming to that conclusion myself, but wanted additional info. "to be sure".
Trev.

[rurwin]

+1

It isn't HDMI, since you tried to boot it without. It's unlikely to be Ethernet, but you tried that too.

Under about 4.6V, the RaspPi won't work at all. So at 4.0V it has already failed.

Either there is some fault on the board that draws too much current, or the fuse is triggering at the wrong current. Either way your Raspberry Pi is faulty.

Send it back and get it replaced.

... just a random thought, but you're not putting it down on a conductive surface are you?