Raspberry Pi Forums

Summary

Reasonably new TV set (Samsung HG28ED690AB ) worked with previous versions of the Raspberry Pi without issues.

Now TV doesn’t detect signal from Pi 4 Model B 4GB, doesn’t display rainbow screen on first boot with NOOBS on the micro-SD, and doesn’t display the NOOBS installation options screen. Replacing the micro-HDMI plug in socket HDMI 0 allows me to see the options screen.

After installation, the same problem occurs, this time with the OS options screen. By the time I reconnect the micro-HDMI, the Pi has booted into Raspian, the first OS on the list.

I have done some internet searches on this, and studied the forum, but I have found no solutions.

I am looking for a permanent fix which doesn’t involve reconnecting, and which gives me the option of booting into another OS. I have kept careful notes on all this, and I can provide more details if required.

Its weird that unplugging replugging seem to fix the problem as the device does not support hotplugging.

Have you tried different sockets on the TV itself?

What resolution is the TV?

Thanks for the quick response.

I have tried all three HDMI sockets on the TV.

I can't find the resolution from the on-screen menu.

More Detail

A new SanDisk Ultra microSD 16GB card is used. It is formatted to FAT32 with gparted.

The NOOBS 3.2.1 zip file is downloaded and unzipped. The contents of NOOBS 3.2.1 folder are copied onto the card using Etcher.

The Raspberry Pi 4 is connected via a micro-HDMI to HDMI cable to a Samsung HG28ED690AB television. The port HDMI 0, next to the power socket, is used.

An official Raspberry Pi Power Supply is connected, and the Red and Green lights turn on. They remain illuminated with no flashing.

PROBLEM: The TV does not detect a signal. I cannot see the rainbow screen, or the NOOBS installation options screen.

I power down the Raspberry Pi, and remove the micro-SD card.

Inspection of the micro-SD card on my Fedora PC shows that NOOBS has created a partition named SETTINGS.

This contains two folders: cache and lost+found
as well as two files: noobs.conf and wpa_supplicant.conf

I return the micro-SD card to the Raspberry Pi and power up. There is no signal detected.

I remove the mini HDMI socket from HDMI 0 and replace it in the same socket.

I can now see the NOOBS installation options screen.

I select Raspian Full, LibreELEC_RPi4, and the Data Partition, and hit Install.


The installation proceeds to completion, and I reach the prompt to quit NOOBS and reboot into the OS boot menu. Upon rebooting, my television reports that no signal is detected. I cannot see the OS selection screen.

Repeated reboots and replugging the micrHDMI cable have no effect.

I decided to make some changes to the config.txt file on the boot folder on the micro-SD card.

After an internet search, I have uncommented the line

#hdmi_safe=1

On reboot, the TV fails to detect a signal, but replugging the micro-HDMI into HDMI 0 produces the Raspian desktop on my screen. This is a positive result, but of course I have not seen the boot option screen which would allow me to boot into LibreELEC_RPi4.

Inspecting the micro-SD card reveals that there are TWO config.txt files – one in the boot partition, and the other in System. The one in System is different. I add the lines

# uncomment if you get no picture on HDMI for a default "safe" mode
hdmi_safe=1

to the one in System, but on reboot this makes no difference. I can still see the Raspian desktop if I reconnect the microHDMI lead in MDMI 0.

I will be pathetically grateful if anyone has any suggestions as to how to resolve this issue.

I really don’t want to keep reconnecting the micro-MDMI to HDMI lead, and I would quite like to be able to chose which OS to boot into. I am exploring the possibility of buying an micro-HDMI to VGA lead, but that wouldn’t really be a very elegant fix.

I have enabled boot logging, but I suspect that as the issue manifests itself before the Pi boots into Raspian this may be to do with the EEPROM. I am way out of my depth here, so this idea may be completely stupid!

Apparently the resolution of the TV is: 1366, 768 px

John Fraser wrote: ↑

Mon Oct 21, 2019 2:20 pm

Inspecting the micro-SD card reveals that there are TWO config.txt files – one in the boot partition, and the other in System.

Just FYI...
You need to treat NOOBS and the other OSes you installed as separate OSes. They each have their own rootfs, boot/firmware files and configuration files etc.

By default, NOOBS does not have a config.txt file, but it is possible to add one.
Create and modify this file to control any unusual video settings that you want NOOBS to use, although it is not normally necessary. Without it, the firmware defaults will be used.

When you select the OS to boot in NOOBS, NOOBS will reboot the Pi into the OS you selected. Therefore, everything you did in NOOBS is now lost and the Pi will use the config.txt file, firmware etc, of the OS you boot into.

The config.txt file you found in the boot partition is for Raspbian. the one in system is for LibreElec.

If you need special settings in config.txt for your TV, you will need to modify the config.txt file of each OS respectively (incl. NOOBS).

Many thanks for that.

The benefit of problems like this, and helpful responses, is that they all help with the learning curve.

I have tried messing around with the config.txt, but beyong uncommenting

hdmi_safe=1

nothing seems to have pointed towards a resolution.

Maybe I should try adding a config.txt to NOOBS with just that line. My suspicion is that I would still have to reconnect the micro-HDMI, but I'll give it a go thisevening.

No doubt you have found this page for configuring the video display: https://www.raspberrypi.org/documentati ... t/video.md

You could try configuring a lower resolution using hdmi_group/hdmi_mode. I read 1366x768 is a tricky resolution for the Pi4, but not sure that is related to your problem. Worth a try though.

The problem with display issues like this is that you can't see what's going on. Fortunately, it is booting and I presume the network is working fine after a replug of the hdmi lead gets the display working. So you could use ssh to get a terminal shell from the pi over the network and use a PC to diagnose what the Pi thinks it is connected to it (HDMI-wise).

Unfortunately, NOOBS does not support ssh, so you will have to wait until it boots into Raspbian. (Enable ssh with raspi-config or configuration from the gui menu). Or for more involved debug purposes, replace NOOBS with plain Raspbian, flashed with Etcher. This will make the debug/reboot cycle slightly quicker for you, but maybe offset by the time taken to rewrite the SD card (swings and roundabouts!)

See if the output of "tvservice -s" differs before and after replugging the hdmi lead to get it displaying. Apart from that, I'm not sure how much more I can help.

Thanks again for your input. Yes, I found that page in my research.

The Pi 4 is certainly booting , and the network connection is up, because I managed to update Raspian.

I will try tweaking the resolution next, and then I will try SSH (another learning curve!).

I am beginning to suspect that the issue may be down to some idiosyncrasy in the TV.

I will try with the TV in the lounge tonight.

That will involve kicking the teenager off his PS4 and suggesting that he does some homework, so it may take a while.

John Fraser wrote: ↑

Mon Oct 21, 2019 3:34 pm

Thanks again for your input. Yes, I found that page in my research.

The Pi 4 is certainly booting , and the network connection is up, because I managed to update Raspian.

I will try tweaking the resolution next, and then I will try SSH (another learning curve!).

I am beginning to suspect that the issue may be down to some idiosyncrasy in the TV.

I will try with the TV in the lounge tonight.

That will involve kicking the teenager off his PS4 and suggesting that he does some homework, so it may take a while.

The TV's native resolution is 1366x768 which is known to be problematic on the Pi 4. The manual at http://downloadcenter.samsung.com/conte ... G-0318.pdf lists the video modes that this TV should support (assuming the manual is accurate) - see page 10, and ignore the table on page 11 which lists the video modes for larger TV models in the same range as yours.

The mode that should be closest to the native resolution of the TV, and easiest to configure, is listed as VESA DMT 1280x720@60Hz. Based on that, the video mode selection table at https://www.raspberrypi.org/documentati ... t/video.md give the following settings for config.txt:
You also need to comment out hdmi_safe=1 to use these.

John Fraser wrote: ↑

Mon Oct 21, 2019 2:20 pm

The NOOBS 3.2.1 zip file is downloaded and unzipped. The contents of NOOBS 3.2.1 folder are copied onto the card using Etcher.

An official Raspberry Pi Power Supply is connected, and the Red and Green lights turn on. They remain illuminated with no flashing.

I'm sorry, but that makes no sense. You don't use Etcher to install NOOBS, and both LEDs illuminated with no flashing indicates the Pi is not booting (the green activity LED should flash when booting).


Try using Etcher to install a Raspbian image and let us know if it works.

Also, try PINN instead of NOOBS (NOOBS never was a good solution, and often causes more problem than it solves).

PINN also includes an Etcher'able version, for folks who can't understand the simple NOOBS instructions.
http://sourceforge.net/projects/pinn/fi ... te.img.zip

Sorry to HawaiianPi. That was a bad text edit on my part. I used Etcher to burn a LibreELEC_RPi4 image onto another micro-SD whilst wrestling with this problem. Just neglected to take the "using Etcher" phrase out when simplifying my notes and drafting the More Details.

Re: the LEDS, I didn't notice the flashing, because I was watching the TV screen, and I'm amongst the 6% of the male population who are Red/Green colour-blind. Wife who has normal colour vision has confirmed that green led does flash briefly. I perceive the red LED as being a LOT brighter than the green one.

I will try a Raspian Image with Etcher, and PINN.

andrum99: I tried commenting out the line hdmi_safe=1, and trying those settings, but I couldn't get a display at all.

DougieLawson: I had never heard of PINN, so thanks.

Thanks to everyone for their suggestions. I will try these things (and maybe a few more) tonight and report back tomorrow.

I should do more advertising!
Even though it's in the signature of every post I make.

By the way, PINN also includes ssh, so you could use that for debugging over the network instead, as per my previous post.

Well, I have spent a couple of hours exploring the delights of PINN, and I think that it's wonderful. I used the Etcher image, and everything went perfectly.

I have set up SSH too, so that is another learning curve to enjoy.

I have surrendered to the idiosyncrasies of my TV and used the VGA socket. It has meant using an HDMI to VGA adapter, and taking the audio directly from the Pi, but the set up works as it is.

At some stage I shall return to the task of getting the Pi's HDMI output to play with the Samsung TV, but for the time time being I am content.

Thanks to everyone for your support. Nice forum, this.

I encountered the same problem (no display signal) and for me it was a loose connection between the HDMI to HDMI-micro adapter. Have you tried this? The adapter seems to fit very loosely in both HDMI jack sockets, causing these loose connection issues.

Had the same issue...tried switching to another micro hdmi cable and it got fixed