echoplex woes- help...

[monk@fuse.net]

i'm having trouble with the 'plex. i just dusted it off for a tour and 
(having gotten it back from gibson repair) and finding that whenever i 
play a loudish note (not coming close to overloading the input) the 
feedback  light lights up and make a digi kind of noise. this ONLY 
happens when i'm recording or over dubbing. if i'm just playing thru 
the unit while not recording, it make none of this noise.  any help 
would be greatly appreciated.

thanks