Sequential circuits samplers

Hi everyone, first time poster here.  I powered up my old P2000 v3.0
today for the first time in years - it had a broken fuse holder and I
managed to source a replacement at last.  Lo and behold, it still
works (mostly)!  The disk drive isn't loading any old disks, but no
big surprise there - I'll go hunting for a new drive.

But the big disappointment - filter resonance is not working at all. 
Filter cutoff works, and everything else (including ROM presets and
all 8 voices) seems present and correct.  It's also sampling ok.  This
is a real shame, as the main reason I kept it was for the great filters.

Any help would be appreciated!

Cheers

Frank

>>filter resonance is not working at all.<<

will hunt out schemos this weekend. you a tech, or know one? seems to
me that something has failed that has 8 chennels, like a d>a or a
buffer amp chip of some sort. you wouldn't get identical failures in
all 8 analogue voices any other way, & still get noises out...

duncan.

Hi Duncan

Thanks for your reply!  Sorry about taking so long to come back here
and check...

> will hunt out schemos this weekend. you a tech, or know one? 

I'm not a tech, but I have been getting into repairing my own synths
in the past few months.  I have a small stock of chips and other
parts, a good iron, a scope and a multimeter.  I can replace
components and run tests, but I don't have enough electronics
knowledge to diagnose complex problems based on schematics, although I
can read a schematic.  And I do know a good tech...

> seems to
> me that something has failed that has 8 chennels, like a d>a or a
> buffer amp chip of some sort. you wouldn't get identical failures in
> all 8 analogue voices any other way, & still get noises out...

Unfortunately it's now worse than that.  I had a discussion going on
the Gearslutz forum where I was making some progress, but in the end
disaster struck, and while I was probing a pin on a chip (pin 6 of
U331), the probe shorted to an adjacent pin.  The P2000 is now out of
tune, and not sounding good at all...  I was planning to pass it on to
my synth tech this coming week, but in case you can think of anything
first, here's a link to the discussion:

http://www.gearslutz.com/board/showthread.php?t=329183

I have some 4051s, TL084s, and some 74HC174Ns, in case the problem
lies with U305, U330 or U331.  If you think it's worth a shot, I can
replace any or all of them, but I want to avoid unnecessary
desoldering on the board, unless it's recommended by someone who knows
more than I do about these things.  I would get immense satisfaction
from carrying out this repair myself though!

Cheers
Frank