Sprint 400 on Novamill - interesting fault (and fix)

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DavidJ
Posts: 16
Joined: Mon 19 Aug , 2013 7:34 am
Hardware/Software: Novamill
Location: Teesside

Sprint 400 on Novamill - interesting fault (and fix)

Post by DavidJ » Sun 20 Mar , 2016 15:55 pm

After months of putting things off, I eventually sorted out re-using the opto isolated 0-10V output on the Denstep board to take a PWM output from Linux CNC (basically same approach as recently reported here in another thread).

However, despite this the spindle would not run at all. One clue was that the 0-10V signal measured at the Sprint board (carefully as it is not isolated from mains) was sending my auto-ranging DVM off scale, but was OK if I removed the mains fuse for the Sprint.

Checking out the Sprint Manual (downloaded from Sprint Electronics, more legible than the copies here), I noticed that terminal 2 (MIN) is connected on board to signal ground via a 5k trimmer pot. Measuring resistance between terminal 2 and COM, I found it to be open circuit (even when twiddling the trimmer). I simply moved wire 84 from terminal 4 to terminal 7 (other COM) on the Sprint, freeing up terminal 4 for the blue wire from Denstep board which had been on terminal 2.

I now have fully working speed control.

I'm assuming maybe a dry joint (terminal 2 to board, or trimmer pot to board). I may investigate further but I now have a working system. I thought I'd post my findings and maybe save somebody else a lot of head scratching.

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