Personal web pages of

Tim Stinchcombe

A-151 Modification for a 2 or 3 Step Sequence

This a nice simple modification originating from Peter Grenader: it allows an old-style A-151 to be switched through just a 2 or 3 step sequence, as well as the default of 4 (this is now incorporated by Doepfer as standard in newer versions of the module). Details of the mod can be found at (the archived copy of) Peter's page of modifications here: I shall only give pictures of my modified module, as it is very simple to do!

This picture shows the location chosen for the new ON-OFF-ON switch, under the line of sockets:

The switch operates vertically, with 'up' for a 2-step sequence, 'down' for 3, and 'centred' for the default of 4 steps. I placed electrolytic capacitor C3 on the solder side of the PCB, to make room for the switch, as seen at the right of this bottom view (I built my module from a bare PCB and faceplate, but it is easy to remove the old one and solder a new one onto the bottom):

Here is a closer look: it is easy to identify pins 11 and 15 of the IC to which to solder the 1k resistors; likewise the 'res in' socket for the diode:

Finally a front shot showing that the switch doesn't look like it is that out of place!:

[Page last updated: 25 Jan 2014]