Raspberry Pi Forums

Hi all,
I have a RPi2 that has been in use for some time without issue.

Last night we had a mains power failure - the Pi was up and running at the time - and now I have no output on the HDMI. I can see it is booting up ok from the green activity light (and have also tried other SD cards that had a working system on them), but nothing on the HDMI.

I guess it suffered in same way when the power went off - but is this a known weak point or I have I just been unlucky?

Get a new 8Gb SDCard and a USB reader.

Build a copy of Raspbian on the new card so you've got a bootable Raspberry Pi.
Mount the unbootable SDCard in the USB reader. Mount the USB reader in a socket on your RPi.

Open an LXTerminal window and run the following command

for i in a1 a2 a5 a6; do sudo umount $i;sudo fsck -f -y $i;done

Power off, swap the cards back and boot your normal system.

Hi,
Thanks for the reply.

The problem I have here is not that the RPi is failing to boot - from what I can see on the green activity LED, it is booting - but there is no video output on the HDMI port.

Just to be sure, I did create a new SD card, which boots up fine on an older Model B I have. But again on this RPi2, the green activity light looks fine, but no video is present on the HDMI. So it does really look like this output has failed.

...after a bit of digging around, I found a video cable that has the correct connector for the analogue output on the Pi and I can see from that it is booting up ok. Just nothing on the HDMI. Sigh.......

..me again.

I tried the 'hold key 2 on boot' to force HDMI safe mode - never knew about this until 5min ago - and it's working again on HDMI

How about that? I guess it got stuck in another video mode somehow... although I have made no changes to config.txt before or after.

rjmusto wrote: ↑

Mon Oct 02, 2017 4:15 pm

Hi all,
I have a RPi2 that has been in use for some time without issue.

Last night we had a mains power failure - the Pi was up and running at the time - and now I have no output on the HDMI. I can see it is booting up ok from the green activity light (and have also tried other SD cards that had a working system on them), but nothing on the HDMI.

I guess it suffered in same way when the power went off - but is this a known weak point or I have I just been unlucky?

When the Pi starts up it checks the HDMI port to see if there is a display present. If it does not detect a display at that point, it switches to the composite video port instead. In order for a display to be detected by the Pi, you usually need to select whichever port the Pi is connected to e.g. HDMI1, HDMI2, on the display itself.

Note that the Pi will only try to detect the display at the very start of the boot process - when power is applied. If you attach a display later, it will not be detected, and you will have to manually select HDMI output in some other way.

You can force the Pi to output on the HDMI port at boot time by adding the following line to the config.txt file:
This makes the Pi behave as though there is an HDMI display connected. Usually you will want the particular video mode to be selected as well. This can be done using the hdmi_group and hdmi_mode options. See https://www.raspberrypi.org/documentati ... t/video.md for the relevant documentation.

Hi,
Thanks for taking the time to write.

I am familiar with the Pi's behaviour with the HDMI output (but forgotten about the keyboard inputs) and have had it set to default to the HDMI output.

Annoyingly, although I had it working for a while last night, the problem has returned. It is booting up ok, but nothing I do results in any video on the HDMI output. So looks like my original suspicion that there is a hardware fault may be true.

Rats.

they display may not be the part that is failing
put
hdmi_force_hotplug=1
hdmi_drive=2
into the correct /boot/config.txt

Tried that - still nothing.