PLAN B analog blog

Sounds like this is a used one, yes?

OK, unfortunately you have to open it up.  Not hard, just have to be
careful.   Remove the knobs (make sure you don't dent your faceplate
if you use a flat-blade screwdriver to lift them off).  The you have toremove the nuts for the pots and the output jack nuts and the 1v/oct,FM in, morph VC row.  do NOT remove the nuts on the fine fune, sync,VC PWM, PWM not and Wave B switch.

The carefully separate the faceplate form the back and you'l see it
open up like a book, with wires going from the main board to the
faceplate mounted components. The wires are long enough so the
faceplate will pay facedown next to the electronics.

First thing to do is check if the wires and soldered jumper is intact
on the fine tune pot.  looking at the back of the pot with the leads
on bottom, there should be a piece of buswire shorting the far left
lead to the center lead.  Then there should be two wires coming off
the pot as follows:

The one coming from the far righthand lead should go to pad FF1 on the
main board.

The second wire, which can come from either the center or far left
lead of the pot should go to a pad labeled FF2 on the main board. 
It's right next to FF1.

If the wires are all on in place, just look down them, inspect them to
see it there are any kinks or cuts in the wire, or places where the
insulation has ripped and exposed the wire strands.  If you see any of
this, replace that wire.

Last thing to check, but really - don't get your hopes up:  R11 may be
missing ( I would kiss your butt in Macy's window if it were).  I use
these to calibrate the tracking when they ship.  If it was missing,
I'd know about it. Anyway, R11 is the 680K (blue/grey/yellow bands)
right next to the FF1 and FF2 pads on the main board.

If all those are intact then you need to check the pot.  Basically I'd
just replace it.  It's a 100K linear Alpha type.  Not sure where you
get then in your neigborhood, but you can get them in the US from
Mouser (they only hace log in that config, but it'll work) or
Futurlec, who will have the pot you need but it may take longer to get it.

Then just slap that pot in place where the old one was.

Feel free to post any results you find here.  Sorry you're havng this
problem.

- P










--- In PLAN_B_analog_blog@yahoogroups.com, "gabu_004" <gabu_004@...>
wrote:
>
> Hello Peter,
> 
> I've just acquired a M15 v.2 where the fine freq pot doesn't do 
> anything at all, the guy who sold me assured me it was working, so it 
> must be the traveling that changed something... do you have any 
> possible diagnostic of what it could be, what I should check, and what 
> I coukld do to fix it?
> 
> thanks as usual :)
> 
> g.
>