Thanks John! I really appreciate your reply.
You were dead right. It was IC3 that was preventing the synth from firing up.
I replaced it with a cheap 7805 from altronics and the unit is working fine.
Do you think it would be wise to replace all of the 7805's and also the 7905 as well - so that they're all new - or is it likely that IC3 only failed due to something further down (do you mean just within the power supply?) drawing too much current (I assume this equates to a failed component).
Is it normal (safe) for the 7805's to be dropping 7v and the 7905 to be dropping just over 8v?
Even after replacing IC3 IC's 2-4 especially are super red hot, despite a rather large heatsink being attached.
Someone mentioned to me that the 7805's and 7905 might be being used for current limiting rather than voltage regulation. Does this make sense? How do i know what the 7x05's are being used for?
Thanks again, Waz