Vintage Synth Repair

hey, i just got a wurltizer 140b but it's amp isn't fully functional,
and is noisey. the "phono" rca jack on the back is the only output
that works. 
i've read that i can reduce noise by replacing the lamp with an led.
anybody got any tips on how to do this and get the amp functioning again?

i'm trying not to let "vintage vibe" get all my money from me, so
maybe there's a hobbyist out there who has documented their work on
this (or similar) models?

thanks,
johnny