Middleby Marshall PS220 Current pickup assembly - side view, Current pickup assembly end view

Figure 16

Current pickup assembly - side view

D. Controller/Motor Failure

When the conveyor speed controller fails, it is very pos- sible that a shorted conveyor motor caused the problem. Unless the motor is changed, the installation of another conveyor speed controller will simply burn up the new con- troller.

You are STRONGLY ADVISED to bypass the speed con- troller and install the tester unit shown in Figure 18 before replacing any speed controller that has burned out. This will identify the source of the problem - the speed controller or the motor. It is much less expensive to burn out the tester than another speed controller.

The components for this tester can be purchased at any electrical supply store. The tester is not as accurate or sensitive as the speed controller, and so should NOT be left in place on the oven after servicing!

SECTION 3 - SERVICING COMPONENTS

Figure 17

Current pickup assembly -

end view

Components needed for the field tester:

•Full-wave AC-DC bridge, 400V, 4A

•Light dimmer switch, 5A

•In-line 5A AC fuse enclosed in plastic case

•2 alligator clips

CAUTION: DO NOT turn the conveyor switch ON while the field tester is connected!

1.Disconnect the motor lead wires and attach to the field tester as shown in Figure 18. Depending on the oven model, you can simply use the black and red gear motor leads, or the remote leads at the terminal block con- nection.

To reverse the conveyor motor direction, simply inter- change the black and red leads.

2.To start the test, the dimmer switch should be turned until the motor begins to operate. The switch can then be turned down to the desired motor speed.

Figure 18

Field Tester for Conveyor Drive Motor

or circuit breaker

15