Looking for a replacement or way to fix my smoked turret encoder on the CHNC II

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03 Oct 2023 15:58 #282170 by Loren
Found the CRT circuitry was fried so we replaced it with an LCD unit, then found the spindle and axes work nice but a whirlygig turret showed another problem. If someone here knows a way to solve this obsolete part problem, let me know? I have work for this machine if I can get it going. converting to gang tool was mentioned but with only 4-1/2" of X travel that seems awfully limiting. I think it's a 1990, it's a Hardinge CHNC II.
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03 Oct 2023 17:36 #282181 by tommylight
Seems like hal sensors, at least i can not see a slot for optical ones.
Should be easy enough to test and/or replace, they react to magnetic field.
3D printing another case/mount would also be an option, if you have to change it.

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03 Oct 2023 18:20 #282185 by Loren
Repair tech said they are reed switches? 

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03 Oct 2023 18:33 #282188 by Aciera

Repair tech said they are reed switches? 

unlikely as those would have bounce. Pretty sure those are hall sensors. I guess your options also depend on the situation like how much space do you have and whether you have a shaft to maybe couple another encoder model to. 

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03 Oct 2023 18:37 - 03 Oct 2023 18:55 #282189 by Aciera
Is this the same or similar situation?
forum.linuxcnc.org/30-cnc-machines/1276-...hnc-1-lathe?start=18

[edit]

looks like it might actually be the very same tantalum cap that shorted.
Last edit: 03 Oct 2023 18:55 by Aciera.
The following user(s) said Thank You: spumco

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03 Oct 2023 19:25 #282194 by spumco

Repair tech said they are reed switches? 

[assuming someone who'd been inside one of these things doesn't come along...here's my thoughts]

Either way, there's a magnet in the turret plate (sub-plate that engages the Hirth coupling) that triggers one of the switches when the plate is rotated to the correct position.  And likely one wire/conductor per switch, plus a power or ground wire.   My guess is that there's no 'encoding' function - just a simple one-to-one position per switch scheme.

Check your cable and see if there are 9 or 10 conductors.  If they're reeds you may even be able to do some continuity checks with a magnet (don't need power for reeds) and see which one(s) are dead.

If you don't want to try to dig out the dead switch(s), it looks like a circuit board potted in epoxy or similar.  Should be do-able to buy a PCB perf board & some hall switches (or reeds) and mount them at the same radius as the original part.  Wire/solder them to a header and connect a cable back to your control - can test the arrangement on the bench using a magnet and a power supply.

If it works, a 3d printed box or mount can be modeled/printed based on the potted board, and the whole thing coated with epoxy for oil/coolant resistance (3D printed parts aren't watertight).

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03 Oct 2023 19:34 #282195 by Loren
There is a  shaft that sticks up just past this to mount the magnet on. There's a bit over 1/2" room under the cover.

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03 Oct 2023 19:40 #282196 by Loren
Magnet mounts on the shaft through this, and above it.

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03 Oct 2023 19:41 #282197 by spumco
I think @Aciera nailed it.  Looks like the cap died and blew off the potting.

Maybe you can just replace the cap and be back in business.

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03 Oct 2023 19:42 #282198 by Loren
This tiny print on the phone is too hard to follow, I'll get back to you on the pc later, but there are 6 leads out of this unit.

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