Hum from on board power supply in an old Ross Flanger... Help!

[Stompin Tom]

So, I have this old ross flanger that I recently fixed by replacing the electrolytic caps (http://www.diystompboxes.com/smfforum/index.php?topic=55292.0). I've been using it regularly since then and I've noticed this hum coming from the unit when I plug it into the amp. This happens both at home at at the practice space (with different amps and nothing else in the signal chain). The schemo for the very similar MXR flanger is here: http://www.shredaholic.com/mxrflanger.html. I upgraded what is the equivalent to c24 to a 1000uf 35v cap and replaced all the other electro caps. On my unit all the other electros are 10uf and the voltage regulator is marked 016 78L 1SA. I looked at various datasheets for the regulator and nothing seems weird to my uneducated eye... So, is there any suggestions to reduce this hum? I don't know too much about power supplies, but it seems like it's reasonably well filtered...