Hi Barf. Thanks for your reply.

After more playing around with the IR transmitter, I have found out that PREV_SOURCE and DIM- only work if they are sent one after another, not as single commands. The VOL_DN and POWER_OFF work as single commands and interact perfectly with the device.

I have tried all the S combinations with D=38, F=84, 256 of them. Unfortunately, nothing more happened than what I already have posted.

Could it be that the device is working on a different IR encoding, but somehow reads MCE encoded signals?

Still did not find volume up command, all thoughts are welcome.