Raspberry HDMI-Ausgang Monitor ohne Bild

[Dieter (Gast)]

Seit einiger Zeit verwende ich einen Raspi 3 mit Raspian als remotes 
Gerätchen. Seit einiger Zeit funktioniert aber der Monitor nicht.
(HDMI, über Adapter an DVI und VGA getestet und verschiedener config)

pi@raspberrypi:~ $ xrandr
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 4096 x 4096
VGA1 connected 1024x768+0+0 (normal left inverted right x axis y axis) 304mm x 228mm
   1024x768      60.00*+  75.08    75.03  
   800x600       75.00    60.32  
   640x480       75.00    60.00  
   720x400       70.08  
DVI1 disconnected (normal left inverted right x axis y axis)
pi@raspberrypi:~ $ tvservice -m DMT
Group DMT has 1 modes:
  (prefer) mode 4: 640x480 @ 60Hz 4:3, clock:25MHz progressive 
pi@raspberrypi:~ $ tvservice -m CEA
Group CEA has 2 modes:
           mode 4: 1280x720 @ 60Hz 16:9, clock:74MHz progressive 
           mode 16: 1920x1080 @ 60Hz 16:9, clock:148MHz progressive 
pi@raspberrypi:~ $ tvservice -s
state 0x12000a [HDMI DMT (4) RGB full 4:3], 640x480 @ 60.00Hz, progressive
pi@raspberrypi:~ $ xset q
DPMS (Energy Star):
  Standby: 7200    Suspend: 7200    Off: 14400
  DPMS is Disabled

pi@raspberrypi:~ $ cat /boot/config.txt 

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

# uncomment to force a console size. By default it will be display's size minus
# overscan.
#framebuffer_width=1280
#framebuffer_height=720

# uncomment if hdmi display is not detected and composite is being output
#hdmi_force_hotplug=1
#hdmi_force_hotplug=7

# uncomment to force a specific HDMI mode (this will force VGA)
#hdmi_group=2
#hdmi_mode=35
#hdmi_group=2
#hdmi_mode=35

# uncomment to force a HDMI mode rather than DVI. This can make audio work in
# DMT (computer monitor) modes
#hdmi_drive=2
#hdmi_drive=1

# uncomment to increase signal to HDMI, if you have interference, blanking, or
# no display
#config_hdmi_boost=4
config_hdmi_boost=8

# uncomment for composite PAL
#sdtv_mode=2

#gpu_mem=64
#dtoverlay=vc4-kms-v3d

Die verschiedenen Ausgaben zeigen jeweils ein anderes Bild, so dass ich 
vermute, dass über die Fernzugriffe mit Grafik (ssh -x, vncviever, 
x11vnc, tightvncserver) etwas "verstellt" sein könnte.