Un-lobotomizing a Maho MH600T

I also had that thought at first. But when I looked up the LS703 scale, I found that they should also have a ~100 mA bulb:
siebert-automation.com/wp-content/upload...ing-Instructions.pdf

You could maybe connect the scale without the ic-nv if you have a board like that and check the current draw. In that case, only the bulb in the scale should be taking some power/current.

I will do more checks for current draw..
These old heidenhain scales are more reliable than cheap chinese 5um quadrature ttl scales ?

I haven't really made any comparison. But I would for sure prefer old Heidenhains over new "chinese" 5 µm scales. For my mill, I do want the 1µm resolution. I could also imagine that the actual accuracy (over length) is better with the Heidenhain scales.

I got the original Heidenhain production calibration reports with my Maho. The worst of the three, had a worst deviation of 0.4 µm if I recall correctly. It would be interesting to calibrate a chinese 1µm scale and see how accurate they are. I would not be surprised if they easily exceed the accuracy achieved by Heidenhain 50 years ago.

According to the certificates of my three 5um glass scales from china the deviation is between 5 and 10 um (max length 400mm).
But of course the price for these is probably an order of magnitude lower as well.

With R2=1k & 10nF Vgate is 364mV (is not exactly the same in all 3 pcbs maybe due to different electric characteristics of zeners )
I have done 2 changes put 1uF multilayer cap parallel to 10nF cap
and put another 1k parallel to R2 so R2 now is 500R and Vgate reduced 250mV (with tic106 triac).
Also connected shield to ground this was the critical fix because the fuses burned when the servo drives enabled
and emf emited from servos maybe trigger the triac.
Now does not burn 0.5a fuses and system works perfect.

I think that i will remove the protection circuit with triac and use protection with p mosfet.

16x interpolation is SF0=high SF1=high ENCODER_SCALE=3200 ?

Tests with 5v supply:
5v1 zener 1k resistor -> 351mV
5v1 zener 470R resistor -> 240mV
5v6 zener 1k resistor -> 101mV
5v6 zener 470R resistor -> 55mV