Aiwa se211 unlock codes universal remote

Hi, bought a AIWA se211 tv without remote. Used a universal remote (worked just fine) until one day I pressed on the remote while it was lying upside down, after which a yellow key appeared. Since then I could no longer change channels. Does anyone know where I can find the code to unlock the tv again? I've been told that I could also use the codes for the original remote on my current remote so if anyone knows where to find those, that would be fine too.

thnx in advance