For some reason my C0 and A sockets have stopped recieving signals. What have I accidentaly switched off?

What is the set up of your S4?

When turning on, does it clear all memory (set to CLR JA)?
Maybe your memory space is full.

Which program do you use? Pr.3?

You don't receive any signal in your software or in your S4 directly?

Doc

i have it on Program 3 and the memory clears each time....For some reason I have just lost those inputs on the S4 itself

Your problem is likely a hardware or wiring problem.

By elimination, I would try those tests whith S4 only (no software):

-whith 2 short wires pluged in banana jacks c0, can I generate a start pulse by
manualy shorting them?

-same thing with c3 and c6? If so, the problem is in the hardwire of the mountain.
Do the "line test", like described on parag. 2.5 in the ALGE manual.

If not, it's a defect of the timer. Not a setup problem.

-likely as above, short the "A" photocell jack by using pins no. 2 (bottom right)
and 3 (bottom), with 2 little wires manualy. It should generate a stop pulse and
you should hear it. Do the same with "B" and "C" jacks. If not, it's a defect again.
If you got a signal from each jack, it's a cable problem from the photocell, or
the photocell itself.

But in fact, it's difficult to conclude that you had 2 cable problems at the same time
when using timer (start AND stop).

With the result of those tests, I would suggest others.

Doc.