Duke DSO 500, Service Manual

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25
SOLID STATE RELAYS
Five solid state relays are used. Three relays
(K1, K2, and K3) are used to control the heating
elements. Two relays (K4 and K5) are used to
control voltage to the magnetron high voltage
transformer primaries.
Location and Access
The five solid state relays, Figure 9, are located
on the right side of the oven. The right side panel
will need to be removed.
Figure 9. Solid State Relays
Safety Issues
• Electrical supply of 208/240 VAC to the
control transformer when POWER switch
is in ON position
• Main POWER switch has 208/240 VAC
present on the input side whenever the
oven is connected to the input power
source
Tools required
• Flat blade screwdriver to remove side
panel, relay attaching screws, and termi-
nals connections.
Operational Testing
The solid state relays are controlled by the control
board. Control board operation requires the oven
door to be closed. Each solid state relay has a
LED indicator that illuminates when the relay is
operated. Each heater is controlled separately by
either relay K1, K2, or K3. When the magnetrons
are to be operated, relays K4 and/or K5 will have
the LED illuminated.
Test Procedure
Disconnect output leads from the relay to be
checked. Set program to operate the relay. Check
for operating voltage across input terminals. If
operating voltage is present LED should be il-
luminated. Check for continuity across output
terminals. After checking, reconnect output
leads.
Replacement
Label and disconnect wires to relay input and
output terminals. Remove screws securing relay
to oven and remove relay. When installing a new
relay, secure to panel with screws. Connect wires
to input and output terminals.
RELAY CONTROL FUNCTION
K1 Upper Heater Coil
K2 Middle Heater Coil
K3 Lower Heater Coil
K4 HV Transformer 1 Left
K5 HV Transformer 2 Right
COMPONENT OVERVIEW