Lubuntu 18.04.1 LTS xrandr not detecting second monitor

Question

I want to connect my laptop to Samsung SyncMasterBX2350 (2 hdmi ports it has) via HDMI.

This is xrandr -q output:

Screen 0: minimum 320 x 200, current 1366 x 768, maximum 16384 x 16384
LVDS connected primary 1366x768+0+0 (normal left inverted right x axis y axis) 345mm x 194mm
   1366x768      59.99*+  40.00  
   1280x720      59.97  
   1152x768      59.95  
   1024x768      59.95  
   800x600       59.96  
   848x480       59.94  
   720x480       59.94  
   640x480       59.94  
VGA-0 disconnected (normal left inverted right x axis y axis)
HDMI-0 disconnected (normal left inverted right x axis y axis)

This is part of lspic -v output:

00:01.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Trinity [Radeon HD 7420G] (prog-if 00 [VGA controller])
    Subsystem: Hewlett-Packard Company Trinity [Radeon HD 7420G]
    Flags: bus master, fast devsel, latency 0, IRQ 35
    Memory at c0000000 (32-bit, prefetchable) [size=256M]
    I/O ports at 5000 [size=256]
    Memory at d6000000 (32-bit, non-prefetchable) [size=256K]
    [virtual] Expansion ROM at 000c0000 [disabled] [size=128K]
    Capabilities: <access denied>
    Kernel driver in use: radeon
    Kernel modules: radeon

00:01.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Trinity HDMI Audio Controller
    Subsystem: Hewlett-Packard Company ProBook 455 G1 Notebook
    Flags: bus master, fast devsel, latency 0, IRQ 36
    Memory at d6044000 (32-bit, non-prefetchable) [size=16K]
    Capabilities: <access denied>
    Kernel driver in use: snd_hda_intel
    Kernel modules: snd_hda_intel

And for all this time I've been trying with both HDMI 1 and HDMI 2 monitor inputs, and all the time it shows "Signalkabel prufen" for HDMI port which IS NOT connected. I am baffled. What am I doing wrong here? Is it cable problem, monitor problem or my OS problem?

Answer 1

RESOLVED:

Nothing is wrong with monitor or PC or Arandr, it was HDMI cable that was faulty. I bought new one and everything was fine (still had to activate monitor using arandr though).