This listing describes the conversion of Lucas Machines equipped with General Electric 'radio-tube-type' Electronic Speed Sensing Relays to a Lucas Precision printed circuit board.The older units are G.E. part number CR7511B11 'Voltage Sensitive Relay' (wired to G.E. Blueprint M-5119288) and are equipped with radio tubes, part numbers 6SN7GTB and GL2050.While radio tubes may still be purchased for repair of these units, several of the other parts that are used on this assembly are no longer available from any source. It is strongly suggested that a conversion to a more modern solid-state Lucas Precision replacement unit be performed instead of attempting repairs to the original unit.This unit may also be used to replace the slightly more modern versions of the 'ER' unit that are 'built up' on terminal strips with discrete components.
Materials Required:
1 108769-C Printed Circuit Board, consisting of:
1 109779-C (4028-41-01) PC Board
1 910297 Relay
1 912088 Potentiometer
1 912320 Capacitor
1 911737 Resistor
1 912596 Rectifier Bridge
1 912647 Terminal Connector
1 910718 6 Inch Piece, Board Mounting Track
1 910211 4-Pole Allen Bradley Relay
1 108769-C Blueprint ONLY
1 Copy, This Listing
The conversion of a Lucas Machine to remove the older, obsolete 'Tube-Type' 'ER' relay unit is accomplished as follows:
INSTALLATION:
- Remove the existing unit containing the radio tubes, being certain that all wires are well marked with the appropriate wire numbers.
- Remove the separate transformer that supplies power to the tube unit if your machine is equipped with one.
- Remove ALL 110 volt supply wiring related to the tube-equipped unit and the supply transformer.
- Install the new, solid-state replacement unit. (Be certain that the mounting screws for the plastic track cannot contact the back of the printed circuit board of the new sensor assembly.)
- Install the new relay.
- Connect 110-volt power to terminal (7) on the solid-state replacement unit.
- PLEASE NOTE that terminal (5) is 'skipped' on the new unit.
- Connect 110 volt common to the new relay coil.
- Connect the (2) input wires from the tachometer to terminals (1) and (2) on the solid-state unit.
- Connect the contacts of the new relay into the existing machine tool control circuit at the same locations that the relay of the tube-equipped unit was connected.Be careful to observe if the contacts were Normally-Open (N.O.) or Normally-Closed (N.C.) and wire the new relay the same way.
- Connect terminal (8) of the solid-state unit to the 'hot' side of the coil of the new relay.
- The additional terminal connections of the new, solid-state unit are not used.
- Be certain that all wires are labeled, and that any unused wires are safely removed all the back to the closest terminal point.
ADJUSTMENT:
- Select the SLOWEST Spindle Speed.
- Start and stop the Spindle Rotation several times and observe the reaction (during motor stop only) of the vertical splined drive shaft (the largest splined shaft) that carries rotational drive power to the machine headstock.
- Adjust the small control mounted on the new, solid-state unit so that the splined shaft stops without coasting or 'kick-back'.Please note that as spindle speed is increased; coasting of the shaft is normal.
