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11
Sentry Express Digital Temperature Controller
Sharing your passion for making jewelry.
Products. Service. Know-how.
Controller Power Input Test Result: less than 20 volts
Did you recently replace the transformer? It may be
the wrong voltage. The voltage is below 20, which is not
enough power for the controller. To find out the cause of
low voltage, continue below:
Controller Input Test #2
The back of the board is still
facing you and the kiln is
plugged in. Remove the
INPUT plug, which is the
white, orange, and blue wires,
from the back of the control-
ler. Touch a voltmeter probe to the white wire and the
other probe to the orange wire.
Input Test #2 Result: Less than 20 Volts AC
There are two possible reason: 1) Low voltage at the
wall receptacle; 2) defective transformer. If wall recep-
tacle voltage is correct, replace the transformer.
Input Test #2 Result: 20 - 24 Volts AC
The transformer is sending correct voltage to the con-
troller. Yet when the INPUT plug was connected to the
controller, voltage was less than 20. This means the con-
troller is draining the voltage and is defective. Return
the controller for repair or replacement.
Problem: Controller display turns on.
No heat in kiln.
Is the relay making its normal clicking sound?
Yes, the relay is clicking
Test the elements with an ohmmeter.
Element Resistance Test
1. UNPLUG kiln/disconnect the power. Open the
kiln’s switch box. Make sure the wires connect-
ing the relay to the elements are secure. If con-
nections are okay, continue to step 2:
2. Touch the ohmmeter leads to the two element
connectors of each element. A no-needle-
movement reading on an analog meter, or
OPEN on a digital meter, indicates a broken
element.
If the elements check out okay, replace the relay.
Note:
To replace relay, see your kiln’s instruction and
service manual.
No, the relay is not clicking.
We know the controller is receiving voltage, because
the display lit. But the voltage from the transformer may
be too low to power the relays. Perform the “Controller
Power Input Test,” page 10. If your controller passes the
Input Test, perform the “Controller Power Output Test”:
Controller Power Output Test
Is the controller sending voltage to the relay? Test
OUTPUT with a voltmeter:
1. UNPLUG kiln/disconnect the power. Remove the 4
screws holding the controller faceplate to the switch
box. Lift faceplate out of box and let the controller
hang on the outside of the box with the back of the
board facing you. Then plug the kiln back in. Program
the controller to fire to 1000°F at FULL rate in Ramp-
Hold mode. Press
START
.
2. Put the voltmeter in DC mode. (It must be in DC
mode when testing OUTPUT voltage.) Touch probes
to the red wire and black wire connection. Measure
voltage when the relay clicks on.
Output Test Result: No voltage at red and black wires
The controller is not sending power to the relay.
Return the controller for repair or replacement.
Output Test Result:10-14 v. at red and black wires
The controller is sending correct power to the relay.
Unplug kiln/disconnect power. Remove the kiln switch
box. Look for disconnected wires between the control-
ler, relay and elements. Check the wiring diagram to be
are connected to the correct terminals. Be sure connec-
tions are tight. If the wiring is okay, replace the relay.
Note:
To replace relay, see your kiln’s instruction and
service manual.
Problem: Kiln switch box ½ amp
fuse keep blowing.
What size fuse are you using?
Correct fuse: AGC ½ A 250V AC
If the fuse is correct size, perform the following test:
Kiln Switch Box ½ Amp Fuse Test
1. UNPLUG kiln/disconnect the power. Remove the 4
screws holding the controller faceplate to the switch
box. Lift faceplate out of box and let the board hang
on the outside of the box with the back of the board
facing you. Disconnect
both wire plugs form
the back of the control-
ler. Then plug the kiln
back in. Apply power to
kiln. If the ½ amp fuse
blows, replace the
transformer. (If the fuse does not blow, the problem is
the board or relay. Go to step 2.)
2. Connect the INPUT plug (orange, blue, and white
wires) to the board again. Leave off the OUTPUT
wire plug (the one with the red and black wires).
Program the controller to fire at 1000°F at FULL rate
in Ramp-Hold mode. Press
START
. If the fuse blows,
replace or service the board. (If the fuse does not
blow, the problem is caused by a short in the coil of
the relay. Go to step 3.)
3. UNPLUG kiln/disconnect the power. Reconnect the
OUTPUT wire plug Reinstall the board in the switch
box. Replace the relay.
