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I just bought two raspberry 4s (1Gb and 2Gb of RAM) and am unable to get the slightest video signal out of them. I tried every combination of the following components:

  • Raspbian buster lite/desktop

  • 5V 3A USB-C power supply / 5V 3A micro-USB with USB-C adapter

  • Amazon Basics micro HDMI cable (mentioned as compatible on the raspberry website) / GoPro compatible micro HDMI cable (by JVC)

  • two different 7 inch touchscreens / a desktop screen (all three work fine with pi 3s)

  • Using HDMI ports 0 and 1

NONE of these produced any image, just a "no signal" on the display. The PI appears to boot normally with the green LED blinking intensively at first. Now I'm tempted to conclude that my raspberry's are defective but they are from two different vendors and the chances of that seem minuscule.

The config.txt has every line commented, except a few near the end :

# Enable audio (loads snd_bcm2835)
dtparam=audio=on

[pi4]
# Enable DRM VC4 V3D driver on top of the dispmanx display stack
dtoverlay=vc4-fkms-v3d
max_framebuffers=2

I can SSH into the PI but I see nothing unusual in the syslog. With my desktop screen on port 0, running "tvservice -l" gives me:

1 attached device(s), display ID's are :
Display Number 2, type HDMI 0

Running "tvservice -s -v 2" gives me the output:

state 0xa [HDMI CUSTOM RGB lim 16:9], 1920x1080 @ 60.00Hz, progressive

So if anyone could suggest other things to try I would greatly appreciate it.

schmop
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  • First thing first is to remove the two different 7" touch screens. There is 50% chance that the old stretch driver won't work with buster. – tlfong01 Jul 27 '19 at 01:08
  • post the content of your config.txt file – Jaromanda X Jul 27 '19 at 09:37
  • @JaromandaX I've updated the question – schmop Jul 27 '19 at 17:22
  • @tlfong01 I'm now only testing on a fresh raspian buster install and on a regular HD screen (that works fine on my pi 3s) – schmop Jul 27 '19 at 17:24
  • enable ssh, ssh into the pi with the monitor connected, and check the logs for any errors. and check tvservice -l - then using the two display numbers (2 and 7?) what's the output of tvservice -s -v 2 and tvservice -s -v 7 – Jaromanda X Jul 28 '19 at 02:23
  • @schmop, I am using Raspbian 10 buster 2019Jul10 version and have no problems with my Philips monitor. I checked my /boot/config.txt and found the [pi4] section same as yours, and other HDMI lines commented out. It is important to use Jul10 version or later. I have been using Jun26 version for some time and only yesterday found that some packages works only for Jul10 version. – tlfong01 Jul 28 '19 at 02:34
  • @tlfong01 I am indeed using the July 10 version – schmop Jul 29 '19 at 12:29
  • @JaromandaX I ran the tests and updated my question. – schmop Jul 29 '19 at 12:32
  • @schmop, I ran your two "tvservice" commands and got exactly the same output. My wild guess is that buster indeed talked to your monitor and got the parameters (16:9, 1920 x 1080) which I think are not default. I can use my scope to check the signals (I do have a HDMI connector breakout for troubleshooting). But it is only if you also have a scope, then we can compare and contrast. For now, I have no more brainstorming troubleshooting suggestions. – tlfong01 Jul 29 '19 at 13:07
  • I googled the following post but don't find any useful clue. https://www.raspberrypi.org/forums/viewtopic.php?t=245419. In the Desktop > Preferences > Screen Config, you can set screen config, but I do't think it helps, because you problem is "no signal", not any resolution problem. BTW, is your monitor really 1920 x 1080 60Hz? – tlfong01 Jul 29 '19 at 13:25
  • @tlfong01 Yes that is the native display of the monitor. Interesting that the pi would know this despite the blank screen. Does that strengthen the case that something is wrong with my cables? The screen works with whatever other model of raspberry I throw at it. I do have a scope but don't really care about fixing this specific device. This is looking more and more like a freak coincidence of hardware failures. I'll just order the most vanilla display cable, then power supply, then a new pi if all else fails. Thanks for the help. – schmop Jul 29 '19 at 14:24
  • @schmop, Yes, Rpi4 has a voltage regulator (a 3 leg thing near the HDMI connector) which connects to the HDMI monitor and checks the parameters of the monitor, even when the HDMI monitor is power off! And I also begin to suspect the micro HDMI cable, since almost everything else seems OK. – tlfong01 Jul 29 '19 at 14:33
  • Some references in case you still need to do troubleshooting: (1) HDMI power circuit on the Raspberry Pi 4 https://raspberrypi.stackexchange.com/questions/99963/hdmi-power-circuit-on-the-raspberry-pi-4

    (2) AN-1998 How to Meet the HDMI 5V Source Requirement http://www.ti.com/lit/an/snva412a/snva412a.pdf

    (3) LM2757 HDMI Power Regulator http://www.ti.com/lit/ds/symlink/lm2757.pdf

     – tlfong01 Jul 31 '19 at 06:05

0 Answers0