Welch Allyn Wall Transformer 76724

Disconnect wall transformer from mains before servicing

Unscrew six Phillips head screws on the back of the 767 using a Phillips #2 screwdriver with a 3" (minimum) shank

Position the 767 on its back and separate the MH-Front from the MH-Back

Ensure housings are not pulled apart abruptly to avoid pulling wires and connectors

Slide the wire tie off of the MH-Back standoff

Disconnect wall transformer from mains before servicing

Follow instructions in Section B-1, pg. 2 to remove MH-Front

Carefully unplug spade connectors of S1 wires from spade contacts of power switch using long nose pliers

Do not cut the wire tie; it is required to keep wires away from transformer body

Carefully unplug the two-pin connectors from the emitter and detector with long nose pliers

Refer to clock instructions in manual PN767036, pg. 5 & 6 for replacing clock battery and changing time.

Remove clock assembly from 767 and turn it over.

Remove three Phillips head screws using a #1 Phillips screwdriver.

Ensure clock module comes out of face-plate.

Check if set buttons have come off during disassembly.

Position buttons on module with holes in face-plate.

Align clock module with opening in face-plate.

Attach clock module with three screws.

Set time and date on the clock.

Resistance Application and Adjustment

Apply calibrated resistance to handle stud using a 5 ohm power resistor (5 watts) in parallel with a 5-10 ohm potentiometer

Adjust potentiometer until current delivered is 750 mA (4.66 ohm nominal load)

Measure output voltage (rheostat full on) using a true RMS meter set on DC scale. Expected: 3.5 VDC +/-.5 VDC

Measure third handle outlet output at slot jacks on right end of main unit. Expected: 7 VAC +/-1 VAC with nominal load of 9.33 ohms

Disconnect wall transformer from mains before servicing

Follow instructions in Section B-1 to remove MH-Front

Squeeze the plastic spring clips on the sides of the switch to force it out of the MH-Front

Align the lighted half of the switch rocker toward the cradles

Disconnect each wire from the old switch one by one and connect to the same terminal on the replacement switch

Press the switch into the MH-Front

Verify wiring conforms to Fig. 1.