Assistance needed with troubleshooting a 1965 10 ' ee monarch lathe

THE 1965 10" EE MONARCH LATHE IN QUESTION HAS BEEN RUNNING FOR QUITE SOMETIME WITH NO PROBLEMS. RECENTLY, THE LATHE STARTED ACTING UP BY TRIPPING THE CONTROLS AROUND 60 RPMs. ALSO, THE SPEED OF THE SPINDLE DOES NOT MATCH THE ROTATION OF THE SPEED CONTROL KNOB. WE COMPARED BOTH LATHES, WE HAVE TWO THAT ARE THE EXACT SAME, AND IT TAKES SMALL TURNS OF THE SPEED CONTROL KNOB, ON THE LATHE THAT WORKS, FOR THE SPINDLE TO SPEED UP WHEREAS ON THE LATHE THAT DOES NOT WORK, IT TAKES MORE TURNS TO INCREASE THE SPINDLE SPEED TO THE POINT WHERE THE SYSTEM TRIPS. WHILE TROUBLESHOOTING THE LATHE IN QUESTION, WE FOUND THAT INCREASING THE SPINDLE SPEED, BEFORE THE TRIP POINT, WOULD CAUSE THE NORMALLY CLOSED AP RELAY TO CHATTER. THE LARGER THE SPEED INCREASE, THE LOUDER THE CHATTER ON THE AP RELAY, BUT THE CHATTER IS NOT CONSTANT WHEN THIS POINT IS MET. THE CHATTER GOES IN AND OUT UNTIL THE TRIP POINT IS REACHED. WE ALSO FOUND THAT WHEN A CERTAIN POINT WAS REACHED ON THE SPEED CONTROL KNOB, OR A CERTAIN SPEED WAS MET, THE POWER CONTACTOR AND THE DYNAMIC BRAKE CONTACTOR CONTACTS BEGAN TO CHATTER. ONCE THE SPEED CONTROL KNOB IS TURNED PAST THIS POINT, THE FL RELAY CONTACTS OPEN SHUTTING DOWN THE CONTROLS TO THE LATHE. THIS HAPPENS IN FORWARD AND REVERSE MOTION. ONCE THE SYSTEM CONTROLS TRIP OFF, THE DRUM SWITCH CAN BE PLACED BACK TO THE NEUTRAL POSITION WHERE THE SYSTEM RESETS THE CONTROLS. NO FUSES ARE BLOWING BECAUSE THE DRUM SWITCH CAN BE PLACED IN EITHER THE FORWARD OF REVERSE POSITION, AFTER RESET, AND THE SYSTEM RUNS UNTIL THE TRIP POINT IS REACHED AGAIN. ANY SUGGESTIONS AS TO WHAT COULD BE THE CAUSE OF MALFUNCTION?

Since Nobody has chimed in, Is it a original Monarch tube Module drive? Check your module/tubes. I don't have a Modular but there is plenty of info here(search) to troubleshoot a Module black box.

RHarman said:

ANY SUGGESTIONS AS TO WHAT COULD BE THE CAUSE OF MALFUNCTION?

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I would look at the C3J - many of the issues seem to center around field issues, and that's the component in that area that's most likely to age out. The C3J is the smaller tube on in the middle of the tube bay, and can usually be found NOS on eBay for not too much (I see one NOS now for $10 with $4 shipping)

RHarman said:

...ANY SUGGESTIONS AS TO WHAT COULD BE THE CAUSE OF MALFUNCTION?

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Stuck caps lock button?

IF YOU HAVE TWO MODULAR 10EES THEN:
Swap the modular boxes and test both lathes
Then swap the C3Js and test both lathes
Then swap the C16J pairs.

After that swap the lathes and you'll know where the trouble is. No, come back here and someone smart will tell you what to do next (not me).

John