Faulty delay pedal

[944cabby]

A mate has given me a faulty chord dl50 delay pedal thats not working to have a look at.
Apparently it was ok but just stopped working.
I've opened it up and can't see any visible damage or loose wires, although when the leads are connected the LED comes on and off ok as you depress the footswitch.
Theres nothing from the "delay time" or "feedback" knobs however when you turn the "delay level" pot up you can hear a loudish clicking sound through the amp.
I'm guessing one of the chips is faulty - any ideas guys?