PLAN B analog blog

The following are directions on how to locate R51 on a Model 11 board
set.  The intention of this post is improve the self-oscillation of
the M11.  Note:  If your M11 self oscillates already there is no need
to do this.  It won't improve it if it's already there.

Hold the module so that the faceplate faces away from you and the two
VC attenuatros are on the left side (component side up of the main board).

Rotate the module slightly away from you so that the face of trim pot
on thebottom board comes clearly into view.

About 3/4 on an inch behind that trim pot you'll see three parts.  Two
are electrolytic caps (both 10uf).  To the right of those is a single
resistor.  It may be 5.1K (green/brown/red bands) and on later modules
shipped it's 3.9K (orange/white/red bands).  Underneath the part is
printed R51.  That's the one you need to concern yourself with. 

If you Model 11 does not self oscillate, then replace the 5.1K wth a
3.9 K.  You can do this by either desoldering the part that's
installed and replacng that with a 3.9, or using a pair of cuters
simply cut the 5.1K out and solder the 3.9K on the backside of the
board to the two pads the 5.2K was soldered to.

Hi Peter,

I'm looking at doing this mod on my rev 1.1 Model 11. Based on your description, I'm 
seeing a 5.6K resistor (green/blue/red) to the right of the caps. Is that possible or am I 
looking in the wrong spot? And should the replacement be 3.9K .25w?

Thanks,

Adam


--- In PLAN_B_analog_blog@yahoogroups.com, "(i think you can figure that out)" 
<peter@...> wrote:

>
> The following are directions on how to locate R51 on a Model 11 board
> set.  The intention of this post is improve the self-oscillation of
> the M11.  Note:  If your M11 self oscillates already there is no need
> to do this.  It won't improve it if it's already there.
> 
> Hold the module so that the faceplate faces away from you and the two
> VC attenuatros are on the left side (component side up of the main board).
> 
> Rotate the module slightly away from you so that the face of trim pot
> on thebottom board comes clearly into view.
> 
> About 3/4 on an inch behind that trim pot you'll see three parts.  Two
> are electrolytic caps (both 10uf).  To the right of those is a single
> resistor.  It may be 5.1K (green/brown/red bands) and on later modules
> shipped it's 3.9K (orange/white/red bands).  Underneath the part is
> printed R51.  That's the one you need to concern yourself with. 
> 
> If you Model 11 does not self oscillate, then replace the 5.1K wth a
> 3.9 K.  You can do this by either desoldering the part that's
> installed and replacng that with a 3.9, or using a pair of cuters
> simply cut the 5.1K out and solder the 3.9K on the backside of the
> board to the two pads the 5.2K was soldered to.
>