Separating power from data micro USB to HDMI
The AMT630A chip inside the monitor is a chip for receiving analog composite video and conveting it to digital to drive the TFT panel.
There is no digital video that is compatible with MHL or HDMI.
You can of course make a cable that only provides the analog composite for connecting it to an older TV directly or using a converter box to make it HDMI.
So the manufacturer simply used a standard connector for non-standard purposes, and thus using existing cables it is possible to damage equipment - therefore standard connectors should never be used for non-standard purposes. The HDMI input of the monitor is now damaged.
Modifying and using equipment for purposes they are not meant for needs awful lot of research whether it can be modified or used for other purposes to prevent damage.