Duke DSO 500, Service Manual

Page: 51 / 80

51
COMPONENT TESTING
MECHANICAL RELAYS AND
INTERLOCK SWITCHES
Mechanical relays K6, K7 and K8, Figure 19, are
part of the door interlock circuit and are activated
by door switches “P” (primary), “S” (secondary)
and “M” (monitor), Figure 20.
Figure 19. Mechanical Relays
Tools Required
• Digital Multimeter (D.M.M.)
Procedure
1. Remove oven right side panel to gain access
to the mechanical relays.
2. Disconnect and label the wires connected to
the relay output contacts of each relay. Leave
the coil supply voltage wires connected.
3. Actuate oven master switch to the “on”, pow-
ered position.
4. With the oven door in the “open” position
check for output contact closure at relay K7.
Check that relays K6 and K8 are inactive
with no output contact closure. If no output
contact closure is detected at relay K7 check
for presence of coil voltage. If coil voltage is
not present check for proper activation of door
switch “M” (monitor), Figure 19.
5. With the oven door in the “closed” position
check for output contact closure at relays K6
and K8. Check that relay K7 is inactive with
no output contact closure. If no output contact
closure is detected at relays K6 or K8 check
for presence of coil voltage. If coil voltage is
not present check for proper activation of door
switches “P” (primary) for relay K6 and “S”
(secondary) for relay K8.
6. If any mechanical relay fails to activate when
coil voltage is present, replace the relay.
7. Testing complete. Actuate oven master switch
to “off”, powered-down position.
8. Reconnect wires to the relay output contacts
of each relay.
9. Reinstall oven right side panel.
Figure 20. Door Interlock Switches (Left)