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