SOLVED R-Pi 4: display issues, did I get a dud unit or am I doing something wrong?

[yangmusa]

I finally found a Raspberry Pi 4 4GB in stock at a local shop! So exciting, it's been sold out everywhere. My impression is it must be a well-deserved smash hit for the Raspberry company.

I've had no end of issues setting it up compared to the R-Pi 3 (insert card, turn on, done), and I wonder if it's because I'm doing something wrong or because I got a dud unit. All suggestions welcome..

It started out innocently enough - it booted to the rainbow screen and just stayed there. Eventually, I figured out the HDMI cable has to be plugged into the left HDMI port..

With that hurdle out of the way, I finally ran through the normal install process, which eventually ended up on the desktop. It looked normal briefly, correct 1920x1080 resolution.. for a fraction of a second, before the display went black. I tried restarting several times, tried editing the settings in the troubleshooting menu, nothing worked. I eventually gave up and decided to move the unit and tidy the cables - and weirdly when I plugged it back in it worked again. But now the resolution was set much too low, so I went to Display Settings - but only 4 resolutions are shown, the highest of which is something like 1280x800 (not at the RPi right now). Also the screen was really dim now, not full brightness as before.

• I tried running rpi-update to see if newer firmware would help - nope.

• I installed all available updates through apt get update/upgrade

• The screen has normal brightness immediately after boot. It only goes dim once it reaches the desktop

• The TV functions normally using smart TV apps, or other sources such as my HTPC

• I'm using a Samsung 1080p TV if that matters

• I tried reinstalling a fresh copy of Raspbian - no difference

• boot, install & recovery screens all run at 640x480 - is that normal? Maybe seems like the hardware isn't even "seeing" the tv?

• I tried installing Manjaro ARM - it's even worse and only sees a single 640x480 resolution, and the screen remains dim.

• tvservice -n reports "no device present"

Performance-wise I'm blown away, it's so much faster than the RPi3. I hope I can resolve these issues and put it to work! If not, I hope we can rule out all reasonable fixes fairly quickly, so I can try to exchange it for a different unit if it seems likely that there's something wrong with the hardware.

[yangmusa]

This turned out to be a combination fo two things:

• The Pi 4 didn't like my micro-HDMI adapter/cable combination. It works fine with another computer, but not with the Pi.. Tried the Pi 4 with the cable from my Pi 3 and it was able to detect the display and boot correctly to 1080p. Bought a new micro-HDMI to HDMI cable and all is good now.

• The dimming turned out to be an error with the TV's ambient light sensor. It was initially intermittent and by coincidence only happened with the Pi 4, so it seemed like a Pi 4 issue. Then it started happening with other sources and I realized it wasn't a Pi issue at all! Found a way to disable the TV's ambient sensor and now the Pi (and all other sources) displays correctly.

Long way of saying - problems resolved. Really enjoying the increased Pi 4 performance!