Strange problem with Mazak QT10N ATC/MC CAM T3

Hi all,

need some help here on pointing me in the right direction.
So I got this CAM T3 control on my QT10N, and out of a sudden it begans working erratically.

You turn on the machine, nothing wrong, no errors. You can home the machine, move the axes, but:

If I try to move the tail body back, it moves the tail body back AND begins to change the tools AND switches C axis. What the heck.
If I move the tail body forward, than it is working fine.

Ok, check the tailstock:
Move tailstock back, tailstock is moving back, AND Milling or Main spindle starting depending on position.
Moving tailstock forward no noticable errors.

On undeterminable switches it randomly drops rapid speeds to zero, rises spindle speed, switches to jog mode, and maybe some other things I have not noticed.

What can cause such an error ?

I have checked the voltages, they are some 11.05-11.15Volts on the control panel switches seems to be OK. (On the power supply it is 11.95V) On the encoder I can read 11.95V as well. All other voltages were well within range.
I have replaced some of the elco capacitors, but testing them afterwards showed good capacity, so this work was unneccessary.

So what can be the problem? Where should I begin to search on? Thanks everyone.

Open the operator panel by the CRT.
Should look similar to this:



You will see a small power supply here, I think there is +5 and +12 Volt outputs,
left side is the DC, right side is the AC input.

I have had broken wires in the cable from here to the CNC chassis that cause weird problems
on machines where the CRT panel slides back and forth like yours.

Does this machine have an air to air heat exchanger on the CNC enclosure for cooling?
There are problems unique to those that do not, and pump shop air through the CNC chassis.
Traces on the I/O boards rotting away,
and on machines with a circuit board holding the relays, the AC lines crossing over to other AC
stuff causing similar problems to what you have,
or over to the low voltage lines causing massive I/O board failures.

Some of these can be real hard to find the root cause.

Bill