Re: [CAD_CAM_EDM_DRO] BEI encoder replacement

Dan Mauch wrote:

> Here is how I fixed my BEI encoder with a bad incandescent lamp
>
> Taken from my web page
>
>
>
> While disassembling the Y axis I noted there was a BEI incremental encoder
> mounted between the ball screw and the servo motor. I removed it and tested
> it. There was no output from channel A, B or the index. I called BEI tech
> support and relayed what I had found. They asked me how much current it
> drew. It was 70 MA. They told me that was too low and I would either have to
> buy a new one for $400 or send it in for repairs and that repairs could cost
> up to $200 if repairable.

Yeah, the 70mA is the electronics draw, it is normally about 200 mA.
The difference is
the light BULB! There is a grain of wheat light bulb in there. I don't
know this specific
BEI encoder, but it is often glued into a cutout in a piece of PC board
right next to the
glass disc.

If you use a 6 V bulb on a 5 V power source, it will run dimmer, and
last a LOT longer
than the rated life. You can probably even put a resistor in series
with it to dim it to
a medium red and it will still emit just as much IR, which is what the
photodiodes are
mostly sensitive to, anyway.

Working in close proximity to the glass disc and other sensitive stuff,
you have to be
REALLY careful, but these definitely can be repaired, assuming the bulb
is actually the
culprit - but if the bulb is actually burned out, you can be about 95%
sure that is the fault.

Jon