Field Loss Relay take some time to close

Simon&Simon's · Oct 29, 2017

Hi guys, the 1966 module drive lathe is plug and run but I have a little issue. The Field loss Relay take 15 minutes after the timer go 60 second to close and keep the Power Contactor close.
The relay doesn't move before 15 minutes. Somebody have an idea? The relay do work since after this 15 minutes everything seem to work well. Button off work, THS work, Spindle switch work too.

Thanks,

Simon

labeeman · Oct 29, 2017

Measure your field voltage while the Field loss Relay is not closing then measure the field voltage after the Field loss Relay has closed.

rke[pler · Oct 30, 2017

You should have full field immediately after starting the lathe. The most likely cause of your issue is the C3J tube, the smaller tube on the tube panel. You should be able to find a NOS replacement for 20-50 bucks on eBay. Note that you need the one with the usual pin base, not any of the other pinout options.

9100 · Oct 31, 2017

Modulars have two mechanical timers, one for tube warmup delay and the other to hold field voltage on for braking after the armature is switched off. They are poor units and replacements are expensive. If the field timer stays on, the headstock will get hot enough to cause dimensional errors. I replaced both timers on the modular I maintain with modern solid state ones. The field timer on your lathe may be doing something funny. If so change to a good one.

Bill

Simon&Simon's · Nov 2, 2017

labeeman said:
Measure your field voltage while the Field loss Relay is not closing then measure the field voltage after the Field loss Relay has closed.

Voltage of the field should be 120v dc right? Where do I measure this? I have a hard time understanding this part of the electrical diagram.

rke[pler · Nov 2, 2017

Simon&Simon's said:
Voltage of the field should be 120v dc right? Where do I measure this? I have a hard time understanding this part of the electrical diagram.

F1-F2, either at the peckerhead or on the screw terminals at the bottom of the DC panel - 18 to F2 will give it there.

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