ibanez ad-9 bypass question

[nightingale]

i friend gave me an old ibanez ad-9 to fix,
the protection diode was smoked so i replaced it.

now when i plug it in,
if iturn up the vulome on my amp i can hear that the delay chip is working, i can hear a very faint ad-9 working correctly.

this leads to my question about the bypassing in these old pedals.

when i plug any cords into the input/output i hardly get any sound.
i get no sound when the delay is bypassed.

when i plug into the dry output i get a perfectly normal volume, so i know that the jacks are ok. i have inspected all of them.

my question is:

is there some sort of actives involved, that maintain the unity volume when the delay is bypassed?

i can only find an ad-8 schematic,
i suspect taht there is a problem in the part of the circuit that "modulates" the delay signal.
whch parts might be suspect?

schemmo: http://www.freeinfosociety.com/electronics/schematics/audio/ibanezad80.pdf

thanks in advance,