As ever, thanks Jerry.

I'm guessing, than, that the two wire plug is the UV LED (which looks
fine) and the three wire on is some sort of photo-sensitive
transistor? Trouble is this just looks like a bare header plug shell
- no sign of semiconductors. Maybe the sensor has fallen off. I
shall have to have a look-see what I can find.

If the worst comes to the worst, is there anywhere I can get new
components? Or should I just abandon the goto function and just point
the scope manually? As a beginner should!

Matthew

--- In Meade-DS-Telescopes@yahoogroups.com, Jerry <crazyj1251@...> wrote:
>
> Matthew,
> The encoder is what causes the motor unit fault. There
> is a light emitting diode that the encoder must spin
> near. When the encoder blocks the light the computer
> sees it as a turn of so many degrees at the motor. If
> the diode or encoder are not working correctly the
> computer doesn't see the motor spin and gives the
> message.
> Most of the time the encoder wheel itself is dirty or
> has grease blocking the windows in between the flats.
> Rarely but possible the diode will go out. It gives
> off ultra-violet light so don't look for it, you can't
> see it without certain filters.
> Clean and align the encoder wheel first and see if
> that fixes it.
> The diodes can be had at Radio Shack I am told but I
> have not gone and looked for them.
> Jerry in Arizona
>