Failed IR remote

[MartenR]

X1 might be something to stabilize the voltage, but I am not sure about it???
Btw did you see J1 (I first did not see it), is this a jumper?

[Sir George]

Yeah, J1 is something I thought of at first, too. But I rather think it's some kind of overvoltage protection (maybe a zener diode or rather a fuse), since it's right between the battery's positive pole and the circuit (except the IR diode's anode).

[Sir George]

Hi folks,
good news: the broken remote works again! 
I replaced the IR LED and now it works like a charm. Hannon from DALnet:#electronics noticed something yellowish in the old LED and advised my to replace it.
So for all of you with a broken remote, that might be a solution.
Thanks all of you for your help anyways! 

BTW, I used the IR LED part number CQY99 from Reichelt Elektronik, if someone needs to know (I had it lying around fortunately): http://www.reichelt.de/?;ACTION=3;LA=4;GROUP=A54;GROUPID=3045;ARTICLE=6832;START=0;SORT=artnr;OFFSET=16;SID=29ZjO496wQAR0AACntaSI18b46ac32b19a7cabe78262b44486880