Doepfer

Hi psm,

> i have an early no-mod 155 and the step button stopped working 
quite some 
> time ago (didn't last long).  i've never been able to find any 
broken 
> connections, i just assumed it was the tiny button contact that 
died.  while 
> we're looking at them, any idea how to troubleshoot this?

If the module still steps OK when a clock signal is applied, then 
your hunch is almost certainly right - the little switch is wired 'in 
parallel' to a transistor, and just manually does what the transistor 
does each time a clock pulse is received (it momentarily connects a 
signal to ground). Thus it appears the switch is no longer making 
contact when pressed. I could describe how to use a short piece of  
wire to test this hypothesis, but you'd have to be _real_ careful to 
connect the right points on the PCB.

> any possibility of the mod also coming along to aid in prolonging 
the life of the 
> step button circuit?  

The only option here would be to mount a beefier switch somewhere, 
which would hopefully last longer than the original. I'm surprised 
that the switch has failed - they look like the sort of thing you 
would find buried behind the faceplate of a VCR for programming it, 
so I would have thought they would have quite a high 'no. of presses' 
life expectancy. Maybe you just got a bad one.

(See my reply to next post on replacing switch.)

Tim