The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)

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awemawson:
Now part of the delay in making this modification has been that I wasn't prepared to risk damaging my replacement RAM card, and I had been waiting until another one became available. This happened a couple of days ago, so I went through an exercise of backing up and restoring to the new replacement card and running it for a few days to prove it was OK.

Removing the "Button Cell" was easy enough, but then I had to attach a flying lead running to the new box while providing cable restraint and yet still be able to use the card extractor cover with which it is fitted. I say button cell, it's nearly the size of a beef burger ! I then used it's two negative plated through holes to mount a 'goal post' of stiff copper wire to act as a cable restraint, passing the wire through a hole that I drilled in the extractor cover.

awemawson:
Next it was the turn of the C size battery that (very oddly) slid into a holder in the rear of the VDU monitor and was wired from there to the back board :scratch:

I decided to solder wires to my spare battery tray, leaving the other wiring undisturbed, and in doing so revealed a totally undocumented fuse wired in series with the battery. My modification keeps this fuse still in circuit

awemawson:
So now we need somewhere to put the box. I made up a shelf that is suspended from the 'roof' of the metalwork that houses the Siemens controller, and is in such a position that the battery holders CAN be accessed from the removable service panel without totally removing the 820T controller, unlike the previous design.

Usual thing - drawn in Autocad, exported to SheetCAM, plasma cut on the CNC Plasma Table by Mach3 and given a zinc rich primer and matt black top coat. Drilling it's mounting holes was 'interesting' from within the small space, but I had installed hank bushes in the shelf, so screws could be accessed from above and outside the enclosure.

It was then a case of plugging it all together, doing (hopefully) one last re-load and testing that the machine still works (which it does).

Now, with the power on, I can remove either or both of the batteries and replace them, and if I need to totally withdraw the controller, the battery box can remain connected, and come with it still retaining RAM

The shelf has a front lip upstand to prevent the box ratting off, yet allowing it to be tilted for planned removal

awemawson:

--- Quote from: hermetic on May 26, 2019, 10:27:26 AM ---Very neat Andrew! Could you not (if needed) put another battery holder in parralell, or switched in, so that you could fit a new battery before removing the old one, or have you engineered out that memory volatility now?
Phil

--- End quote ---

Phil,

The original (Beaver) design precludes that, as you can't actually get at the batteries, but with my new layout I can easily get at them while the power is ON thus RAM data is retained.

RussellT:
Very neat! :clap: :clap:

Your problems with sticky backed baize reminded me of a technique I have used effectively a few times. I discovered this when attaching golf club grips to a dinghy tiller extension. Golfers use double sided carpet tape and stick that to the club and then wet the grip and tape with white spirit and that makes the glue really slippery so the grip just slides on. I have adapted this when trying to position sticky backed tape inside the dinghy centreboard case. Wetting it with white spirit makes it easy to slide into position. I wonder whether this would work with the sticky backed baize.

Russell

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