Spindle Revs Behaving badly on X4 plus

[DAYG]

At any moment the revs can drop from programmed value to sometime 1/2 of programmed value, From 1-2 seconds before revs pick up again.
it does not matter if M/C is in Manual or CNC mode.
I have done a couple of jobs on the M/C and its Killing cutters.
The spindle revs have no integrity.......
Any ideas would be appreciated ?

[neilw20]

If you are running at maximum speed, and it happens in manual and CNC mode, I have seen this.

Reduce the maximum speed slightly.
Whether the machine is reading the front panel pot or the CNC pwm, the a/d converter overflows if input signal is too close to rail voltage,
causing the converted value to wrap to a small value.

Software bug. Little chance of fixing the firmware that causes this.
In CNC mode reduce your maximum speed slightly until it works reliably regardless of temperature and supply voltage.

For manual mode, put a preset potentiometer, 1K would most likely be OK, in series with the clockwise end of the pot. This allows you to reduce the maximum output of the pot.

I was not able to check the PCBs when I saw the fault, so I am not sure if any adjustments are possible.

If you find a circuit, (in your wildest dreams), post it, and I will know for sure the easiest way to fix this.

[DAYG]

Hi Neilw20, thanks for your reply, sorry its taken a while to get back. I've been away for a few days.
No the revs are not at full speed, the revs drop can occur from any rev setting.
It may sometimes go for a good long while with no change and then it can return with a vengeance.

[neilw20]

Search high and low for loose connections including earth screws, damaged wires, BAD CRIMPS, poorly fitting fuse clips, and examine the PCBs for suspect looking solder joints.
Also wiggle the terminals on the front panel speed pot. They are also of a crimped nature.
Hall sensor circuit board inside motor could also be a culprit.
Does this happen at any temperature?