Start Circuit; Fill Circuit; Wash Circuit - Dexter Laundry T300 Parts & Service Manual

Electrical Path Circuit Schematics

Start Circuit

Power travels into the machine on L1 & L2 & (L3, if 3 phase used). L1 and L2 provide 208- 240VAC to
the controls transformer which steps the voltage down to 120VAC for the controls.
tion at the controls transformer must be checked at start-up to coincide with machine operating voltage)
The 120VAC travels out from the transformer on either [X-1 red wire directly to the 1.5 amp fuse] or [X-1
black/red wire to TB-4 and then through the red wire to the 1.5 amp fuse]. The controls transformer also
creates a neutral on the X-2 black/blue wire that connects to TB-1. From the fuse holder, 120VAC travels
on the red wire to the #6 terminal on the terminal strip and then through the black wire to another step-
down transformer. From the terminal strip the blue wire will provide the neutral for solenoid, thermoactua-
tors and all valves. The white wire provides the neutral from the terminal to the step down transformer.
120VAC is stepped down to 24 VAC (blue wires), 24VAC (red wires), and a yellow center tap wire to the
P-7 power connection on the main controller PCB . With the main control PCB now powered, 5VDC will be
present between the (2) yellow wires and also the (2) brown wires for the coin switches. Both pairs will
now be ready to count coins through the P-2 connection at the control PCB. 26.8 VAC goes out on the
black wire of the P-4 connection from the main control PCB to the S5 door closed switch which mounted
on the hinge side of the front panel. Closing the door will engage the door closed switches, sending the
voltage to the red wire on the S1 door latched switch. Turning the door handle to the vertical latched
position closes the S1 door latched switch, returning the voltage to the main control PCB on the white/red
wire at the P-4 connection. 26.8VAC is now present at the S2 and S3 door locked switches.
26.8VDC is also at the black and white wires between P-21 at the main control PCB and the P-20 of the
relay PCB. This voltage signals the relay PCB that the door is closed and latched making 120VAC avail-
able to the relays controlling the door lock gear motor assembly, drain valve and water valves. A continu-
ous 5VDC is sent on the red wire from the P-1 connector on the main control PCB, through the (normally
closed) emergency stop button switch and returns on the second red wire back to the P-1 connector. After
selecting the temperature, payment is added and the display counts down on the main control PCB display
until the vend price is satisfied. The display will change to scroll PUSH START and the green light over the
start button will flash. Pressing the start button on the front of the main control PCB signals the relay PCB
to lock the door and 120VAC will go to the door lock gear motor on the white/red wire from the P17 con-
nector of the relay PCB. The door lock gear motor engages and pulls up on the door locking rod, locking
the door and closing the S2 and S3 door locking switches.
The S2 locking switch is a backup to the S1 latching switch so that once the cycle starts the S1 isn't criti-
cal. The S3 locking switch provides 26.8VDC on the orange wire back to P4 connector at the main control
PCB and the P15 connector at the relay PCB. This signals that the loading door is closed,locked and safe
to continue wash operations. This activates the P-13 and P-14 yellow enable wires to the inverter drive
to allow motion. If there is no signal on P-15 (orange wire) their will be no motion of the tub. S1, S2, S3
and S5 door switches are now closed . The green "On" LED and the door lock solenoid (discussed in start
circuit) will remain on throughout the cycle.
Fill Circuit-Warm
The relay PCB supplies 120VAC to the brown/yellow wire from P-17 to the drain valve which closes the
valve. The lock thermoactuator also receives 120VAC on orange/blue from P17 of the relay PCB. This
device prevents the door lock solenoid from dropping out and unlocking during the cycle in the event of a
power loss. The 120VAC will cycle on and off keeping the lock thermoactuator engaged until 70 seconds
before the end of the cycle. The main control PCB sends data commands to the VFD through the data
cable connected at P-6. These commands control the wash basket which will tumble one direction for 12
seconds, pause, and then reverse direction for 12 seconds.
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(The L1 connec-
The prewash or wash LED will illuminate at this time, powered through the white wires from the P-3 con-
nection of the main control PCB to the LED printed circuit board. Using the factory preset cycle as an
example: The washer fills the tub through the back of the machine with either one or both the C1 cold and
H1 hot water valves. From the P19 connection of main relay PCB, 120VAC is sent out on the white/brown
wire to the C1 cold water fill valve and the red/yellow wire to the H1 hot water fill valve depending on the
temperature selected. After a 90 second delay from the beginning of the wash cycle bath only, the deter-
gent dispenser flushes the detergent into the tub for 20 seconds. This is accomplished when 120VAC trav-
els through the red/orange wire to the H2 hot water valve solenoid. During the machine fill, a 5VDC signal
is sent on the red wire from the P5 connection of the main control PCB to the pressure switch contact and
returns on the yellow and orange wires to the P5 connection of the main control PCB. When the water
level in the basket reaches the preset level pressure, the switch moves the switch contacts to the full or
open position. This causes the main control PCB to signal the relay PCB to shut off the water valve coils.

Wash Circuit

Once the machine has achieved it's water level, the wash basket will continue to tumble one direction for
12 seconds, pause, and then reverse direction for 12 seconds. The time on the front display will count
down as the bath progresses. The time of the bath is programmable up 15 minutes per bath. Note: When
programming cycles, the wash bath must be programmed for 3 minutes or more.
Drain
When the program bath time ends the main control PCB signals the relay PCB to remove 120 VAC power
from brown/yellow wire at P17 going to the drain valve. The normally-open, spring-loaded drain valve
opens allowing water to exit the machine. This resets the pressure switch back to an empty level and
restores the 5VDC connection through the pressure switch from the red wires to the orange and yellow
wires.
Rinse 1 & 2
For Rinse 1 & 2, the rinse LED will illuminate, the drain valve will receive 120VAC and close. The basket will
fill and tumble the same as the wash bath for the programmed time. The rinse water temperatures are
programmable and factory default is cold.
Final Rinse Circuit
The final rinse LED will illuminate, the drain valve will receive 120VAC and close. The basket will fill and
tumble the same as the previous baths for the programmed time. The final rinse water temperatures are
programmable. Note: When programming cycles, the final rinse bath must be programmed and cannot
be set for less than 3 minutes. Also at the beginning of the final rinse bath, the main control PCB will sig-
nal the relay PCB to send 120V to the P-19 connector on the white/blue wire to the C2 cold water valve for
20 seconds to flush the fabric softener dispenser.
Spin Circuit
The spin LED will illuminate and the main control PCB sends a signal to the variable frequency drive via
the data cable at P6 to VFD RJ-11. The rotation as viewed from front during spin will be counter-clockwise.
(The 18lb washers will extract in a clockwise direction) The time of the spin cycle can be programmed.
Note: The final spin must be programmed into the final rinse bath and must be programmed for 1 minute
or more.
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