Dear Stephan,

so it is appears to be a faulty primary (lower) LFO which is located at the
lower control board, left side in the middle.

1) If the LFO is not running at all:

Check U11 (LM324) - eventually swap for a minute with e.g. U70 or U71
(TL084) and see if LFO is now running. Else check U2 (4053)- swap for a
minute with e.g U153 of upper LFO.


2) If LFO is running slow, but does not change frequency when twisting pot
on control panel or changing programs:

Check U43 (TL084) on lower control board - eventually swap for a minute
with e.g. U70 or U71
Then Check U45 (4051) on lower control board - eventually swap for a minute
with e.g. U46 or U50

3) Above all and in any case, always consider to check the Modulation Panel
(Bender and 3rd LFO) first. THIS is the HEART of the OB-Xa (also OB-X). If
something is wrong there, nothing will go right with modulation (LFO, S/H)
or tuning of the main section and voice boards.

BTW: Make yourself comfortable with the principal function of each element
inside the Obie, before making any adjustments or repairs.

Good Luck!!