Working through an issue with a machine that sat for several months. Ran fine before but now getting a 350 Alarm for axis encoder issue. Diag 202 bit 4 is a 1 for a PHA issue. Machine will fire up and usually without error but when trying to jog, machine will typically only get .010-.020" and throw the Alarm.

I have verified with meter testing that the wiring does not have any obvious breaks as everything tests decent. Probably more resistance than I would like to see but very difficult to get good contact with the meter probes in the cable plugs.

I also verified a perfect 5V going to the encoder from the main control.

I removed and opened the encoder and there is nothing that stands out as 'totally screwed'. The glass disc appeared ok but the microscope told a different story and there was a foggy haze on it with particles on it. I very carefully cleaned the top and bottom with isopropyl, gauze, and very gentle contact. Because the encoder is built with the disc sandwiched between the Aluminum housing and the top PCB, getting at it is extremely difficult.

After cleaning, the machine will jog a little more and it was previously on a hard fault every time it was started and now will only Alarm when jogged. I do not feel my cleaning was adequate.

My questions are:
The disc seems to be glued to a shaft that goes through the bottom of the housing. On the bottom there is a bearing and the slotted driver lug. I have no idea how that comes apart? Obviously this would have to be a very delicate process. Any advice on this? The bearing does not feel good and really should be replaced anyway.

Also, I cannot determine where the actual reader head is located? there is a 4 pin ribbon that connects to a flat device that is glued into the housing and looks up at the disc. They probably run about .020" apart or less. On the PCB that sits above the glass disc, there is another device there. I suspect the top one is the LED light source and the bottom is the reader? The gap between the glass disc and the device on the PCB is quite a bit more. I would say .080".


For these reasons, my cleaning was limited to just the top and bottom of the disc, not the readers and such, as I have no way to get in there or even verify my work is lint free. It seems my option now is either try to go a step further and do it right, send it in for repair (idea on price?), or buy another.

I am also hoping that isopropyl is safe for this work? I was finding conflicting answers and I figured contaminates were better addressed with a mild solvent and did not think there would be a coating on the glass that could be damaged? Under the micro, I could certainly spot small imperfections in the glass. Many appear to be in the glass itself. Maybe these don't have to be absolute perfection to work right, or is this something to look more at?