Hello,
-I'm trying to buy a mill however it has a Z axis problem. I have used several pointers from other posts to try to pinpoint the problem. When I reset the drives right away the Z-axis drops until the brake comes back on. The display seems to be keeping track of where the Z is located though (ie. X and Y are still at home 0,0 but everytime the z drops it records more in the negative as it should).
-I tried changing the homing sequence and swapping drive boards with no success. The machine is a 1993 with a B serial number control. I have a monitor hooked up as the CRT just went out too. Very low hours on the machine as it has been used only at a school for a few hours a year. I did notice when plugging the Z axis wires back onto the drive board I got a little spark hooking one of the wires up. This scared me enough to quit working with the electronics for now. None of the other boards or axis connections did that. Breaker was off and machine powered down (careful to stay away from the capacitors).
-I have to let the machine sit with the breaker off for about 20 minutes for the Z axis to drop upon hitting the reset button. I get the normal 450 error and press ESC and then hit the reset button. Once the Z drifts down it trips out to a 409 error. I cancel that one out and try to go into HDW, MDI, or HOME and I get the 449 error.
-Someone else checked voltages to relays and tested them out, they are said to be fine. The limit and home switch were also tested for continuity and said to be fine as well.
-I did notice a wire broken on a diode connected to one of the capacitors but opted not fix that yet as I'm unsure exactly how to do so safely.
Any tips?