Encoder Fault

[jamesgates1000]

Hi all,

My Denford Cyclone has been out of action for a while and now I have some time to try and fix it.

It had an intermittent fault last year, (It would spin past the tool it is indexing too then do an extra rotation before stopping on it. Sometimes it would immediately move to the part other times it will wait for anything up to a minute then move and sometimes it didn't move at all. Occasionally it would just spin over and over.)
I solved this by replacing the nylon bumpers, locking proximity switch and cleaning a load of oil out of the encoder.

Now the problem has come back, any tool change apart from to tool 1, the turret just spins infinitely.

The encoder has 4 pairs of photoemitter/photodiodes inside and slots for the on and off positions. All of the bits are as they should be except bit 4 which is only meant to be high just for tool 8 but is constantly high. I have checked the others with a multimeter and they register 24v when over a slot and nothing when the beam is broken.

But the one which corresponds to bit 4 is 24v either way.

Does anyone have any idea what the problem could be?