--- 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.

Actually, the LEDs are infra-red, not ultra violet.
That means that you -can- "see" them, if you look at them
with a video camera's electronic viewfinder (a digital
camera's display screen will probably also work... i've
only tried it with a video camera)


> 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.

Simply having the LED or photosensors dirty can cause a MUF,
or having them knocked askew so that they're not seeing
eachother through the encoder vanes. The photosenors is
really -two- detectors (it's called a quadrature detector),
and can be swamped by ambient light if you're running it
in daylight... keep it in shadows when testing.

good luck
--dick