Comm loss is driving me bonkers

[Stagecraft]

Have been running this older, upgraded Shopbot PRT Alpha and Colombo 5HP spindle for years with few issues. I've been controlling it with a Sony Vaio which has been absolutely bulletproof...until now. I retired 18 months ago and I kept one of my Shopbots for hobby work, I'm just getting it put back together now. Everything is grounded, I can power everything up and move/jog the gantry all over without issue except for when I start up the spindle. Each time I turn it on I get a comm loss message within 5 to 10 seconds. I've tried updating the firmware, checking all connections, ensuring my power and data cables are separated etc. The computer is a standalone and not connected to the net. The only way I can re-establish the comm is to do a hard boot of the PC...any thoughts???

[Brady Watson]

Make sure your 5 and 24v power supplies are working to full voltage and check the contactors for control and spindle.

[Stagecraft]

Thanks Brady. Forgot to mention this is a Colombo spindle without speed control through the control box. Will go re-check all connections and voltage next.

[SteveNelson46]

Try changing the usb cable with a good high quality shielded cable. It may not fix the problem but it's the easiest place to start and certainly can't hurt anything.

[Stagecraft]

Yup, that'll be next. There is a shielded cable on there now but things do wear out. This machine has been very reliable and at times has run for ten hours a day, five days a week.
When I closed my shop I disassembled the table and disconnected all wiring between the Shopbot and control box. The machine sat for about eighteen months while I waited for construction of my home workshop to be completed. I put everything back together the way it had always been. Everything is steady and works as it should right up until the spindle is rotating. After a few seconds of the spindle running, up pops the lost comm message. This isn't one of those random comm issues as it is repeatable and exhibits the same behavior every time.

[srwtlc]

You may need to have a filter on the spindle now due to some difference between building wiring from old to new shop. Make sure you have some separation between the spindle wiring and USB.

[Stagecraft]

Problem solved, thanks to all that offered suggestions. Turns out it was a harmonics issue with the PC and control box having the same power source. In the end it was our electrician that figured it all out; when he explained what was causing the problem I just looked at him and nodded my head like I knew what he was talking about. ;-)

[Brady Watson]

Turns out it was a harmonics issue with the PC and control box having the same power source.

Ground loop?

Glad you got it sorted.