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I ask for help in diagnosing the drive. The problem is that there are only 20 volts on the DC bus. I have removed the drive from the machine and am trying to find the problem. The question is, does voltage appear on the DC bus if the signal connectors are disconnected from the drive?
https://i.imgur.com/lF4FQXQ.jpg
Yes , it will appear , you can hear a sound of switching relay inside the drive after a precharging
circuit with mos transistor and a couple of charging resistors .. ( precharge of capacitors of DC bus)
I recently repaired one . I've repaired 3 total. Mine 2x and a buddies. Honestly , you can do it a few ways if you are a bit on the novice side in the EET space. a) inspect and test for damaged components. b) Then replace suspect components. c) while inside, if old, elect to uplift and refresh some of the the key power components like the 3 phase rectifier, the 2 power caps, the regen IGBT, and possibly the spindle IGBT's. It's not that hard to at least open up and look for hot, burnt, damaged parts and go from there. IMO. I know this post is late... but just adding some notes for future folks. I have a lengthy post over in PM on the rebuild I did on a 98 unit, and all parts needed via Digikey for the 15/20 white unit rebuilds are blowing $1200 and 2x back and forth for non-repairs.