Bridgeport R2E4 BOSS 9 Pulling Excessive Current - Help Narrowing Down Possibilites

Machine hadn't been powered on for 6 months, when I went to inspect it the owner turned on his RPC and about 2 minutes after the machine turned on, before being homed, the RPC almost stalled due to excessive power consumption. The owner claimed it worked up to that point.

Now the mill is in my shop and I've narrowed down the problem to the power supply for the servo amps (probably). I can get the machine to boot and pass all tests, but I can't get any axis to move.

With the VFD monitoring current and the power supply connected it will draw up to 15A, at which point my VFD faults due to overcurrent, no fuse is blown. If I disconnect either the 70 or 90 VAC input lines the drive won't fault; keeping the 70VAC line connected I get 1.8A load, 90 VAC is 3.2A.

I attached two relevant wiring diagrams and a picture of the circuit. Disconnecting line 214, 215 or 2 will prevent the fault. 215 is tied to 252 via a thermistor, 215 isn't actually connected to anything else, same story with 251 to 214.

I've disconnected every output from the power supply with no luck. Values aren't specified for any of the components, and I'm not familiar with the circuit, so I'm not sure what an acceptable range should be for the resistor, I measured it at .6ohms.

I'd like to get the machine running for testing purposes. I plan to convert it to LinuxCNC, so I'd like to make sure at least the servos are functional, and if possible, reuse the servo amps.

Diodes D5 and D6 are continuous, which would explain the problem. Ordered a new set and an extra just in case.

That boss control has got to be one of the worst controls ever made, I junked mine and put a Centroid on about 10 years ago. Best thing I ever did with this machine.

moonlight machine said:

That boss control has got to be one of the worst controls ever made, I junked mine and put a Centroid on about 10 years ago. Best thing I ever did with this machine.

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Agreed, I'd sooner do this than go LinuxCNC. Not very many DIY retrofits around that are actually functional (although you have a head start having no toolchanger or prox switches etc to worry about).

Are you running a VFD to power the main lugs on the machine? It's pretty likely that won't work as my understanding is a VFD responds poorly to being disconnected from the motor when live. I may be wrong though.

isaac338 said:

Agreed, I'd sooner do this than go LinuxCNC. Not very many DIY retrofits around that are actually functional (although you have a head start having no toolchanger or prox switches etc to worry about).

Are you running a VFD to power the main lugs on the machine? It's pretty likely that won't work as my understanding is a VFD responds poorly to being disconnected from the motor when live. I may be wrong though.

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Centroid can and most do support VFD speed control. I have a V2xT Bridgeport with the Centroid M420 control, It is WONDERFUL! Dead easy to program and reliable as well. It is so nice to be able to turn it on, home the axis and make parts with no bulshit what so ever. I used to be relieved when the boss control would boot up and home with no issues but after a couple of years fighting it and dumping thousands of dollars in EMI's bank account I had enough, I installed the Centroid myself, it replaced everything except the limit switches and the spindle motor. It made a real machine out of it.

isaac338 said:

Agreed, I'd sooner do this than go LinuxCNC. Not very many DIY retrofits around that are actually functional (although you have a head start having no toolchanger or prox switches etc to worry about).

Are you running a VFD to power the main lugs on the machine? It's pretty likely that won't work as my understanding is a VFD responds poorly to being disconnected from the motor when live. I may be wrong though.

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Yes, I am running a VFD to power everything right now, this is only for testing purposes though. The VFD will fault if the spindle is turned off while the machine is under power, but I'm re-wiring the machine controls for 240V, and keeping the VFD for just the spindle.

LinuxCNC will cost ~$350 compared to $2295 for the equivalent Centroid controls. I'll most likely spend 100 more hours on the retrofit for LinuxCNC, but I'm willing to make the trade.