VMC 1300 Pro spindle fails to rotate

[johnparker]

My VMC 1300 Pro has occasionally failed to turn the spindle on program start. The machine traverses XYZ with the spindle not rotating. Usually, homing and trying again resolves the problem.
The issue seems to be getting worse – happening more frequently and requiring machine power down/up to get the spindle rotating.
To diagnose the issue I plan to remove the rear cover so I can see the MicroFlex status LED and look for error blinks.
Any other suggestions? I did consider swapping the Spindle relay and the (unused?) Vacuum relay to see if the relay is getting old, but will await LED diagnostic.
H01093
Feb 2009
Spindle Motor 2.1 HP 1.6 kW 3 Ph
Electrics U0812150073

[Martin]

As you say it is worth checking the MicroFlex spindle drive. If it has a error it will have a red blinking where you count the number of blinks to determine the error.

[johnparker]

Writing up the conclusion of this problem in case others experience. It seems contacts on the door electromagnetic lock switch intermittently fail to close, causing the spindle not to turn. The door lock (Bernstein on my machine) has confirmation contacts (31 32, see circuit diagrams in this forum) that should close when the electromagnet locks the door. Sometimes mine don't - usually it works when the door next locks.

I was confused because V5Milling software Status says Ready, not Door Open, but this is because the software monitors contacts 21 22 which are controlled by the door open/close plunger, and are independent of the lock confirmation contacts.

[Steve]

The Bernstien Guard switch contacts sometimes bounce when the solenoid locks. This is generally the case with older switches and we made a change to the software to try and minimise this. The guard switch type has varied over the years and the earlier switches had contacts rated for higher currents but as the contact is used for signalling then any oxidisation on the terminals over time can make this an issue. The current switch used has gold plated contacts and was selected to prevent this occurrence.