BBD delay : hi freq' tone on output?

[lazydog]

hi, i have a europsonic 802 BBD delay (the generic design used by monacor, BST,
and others) and have just noticed a constant high pitched frequency on the
output - is there an obvious cause for this fault? someone has suggested 'a cap'.

i have another one of these, no problemo at all

cheers

(and please suggest what mods can be done to this baby!)(anyone got a schem?)
D