oliver7
Plastic
- Joined
- Jan 10, 2017
- Location
- Hutto, Texas
Our QT-15 lathe with a T-32-2 controller has lost it's ground on all 24Volt ground terminals.
When I measure voltage on the plus and minus of the power supply I get correct voltage, but when I measure positive to machine ground I get nothing,
and when I measure negative to machine ground I get 24Volts.
It literally appears that the electron flow is going backwards through the 24VDC power supply.
The Multimeter is showing negative 24V when my black lead is connected to machine ground and the red lead is connected to negative of the power supply.
I verified with all our other Mazaks in various condition (controller on/off. Machine on/off etc..) and the entire 24VDC system has constantly continuity to all grounds with a 0.2 Ohm.
The resistance of through the positive side of the 24V circuit is on all of my machines around 300 Ohms.
The resistance from the negative wire into my 24V circuit to ground on the faulty machine is 39 MOhm when connected with the positive clamp to the neg. wire and 16MOhm when I reverse it.
Some component of my 24V system is not getting ground and it pulls the power though the power supply "backwards".
I have never seen anything like it.
Anybody out there that has seen anything like this?
I replaced the 24V supply with three other units and had all systems isolated from each other, but cannot get ground into my G24 labeled terminals.
I am just about to exchange entire components like front panel of control, PCBs of junctions and mechanical relay board PCB.
I rejuvenated the entire ground bar at the bottom of the e-cabinet, I also had the 24V power supply isolated from the machine's 100VAC supply and ran it with outside 120VAC.
But when I take my Ohm meter to the bare wires plus and minus of the 24 volt circuit, my resistance is through the roof.
If anybody has a good tip to isolate the component that pretty much blocks my ground side of the circuit that would help a lot.
Now, additional information that might help, the transformer had cooked one leg coil so my spindle servo overloaded on two phase and blew a component .
I had the spindle control rebuild and use an identical transformer from an AJV right now for trouble shooting.
All in and output voltages are correct.
Also, when I run a separate wire from the ground bar to the negative of the 24V power supply, some machine ready and machine fault circuits are closing and the hydraulic power unit comes on.
But my control gives me a persistent NC alarm and a 128 Emergency Stop error, which I have extensively trouble shot through its circuits already.
I have re-initiated the control, I have had the NC send out to Mitsubishi (no fault found) and have triple checked all my spindle control parameters.
But after I was done with all of that, I could not ignore my 24VDC problem of not having ground connections on my G24 terminals.
Thank you for any input that focuses on my established main issue of not having connectivity on my 24V ground side.
Oliver