Specifications

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(1). The lamp should not light. If the lamp does light, the SCR is shorted and must be
replaced.
(2). If check (1) was satisfactory, test the SCR for its ability to be turned on by the gate.
Connect positive through two diodes to the gate terminal. If the gate is operative, the lamp
will come on and remain on when the gate is removed. Some SCRs will operate correctly
even if the lamp does not remain on, particularly with a weak battery.
(3). If the lamp cannot be lit under step (2) the SCR is open and must be replaced.
NOTE:
If you do not have a test light to check the SCRs as described above, they may be checked
for shorts and opens by use of the VOM.
Measure resistance from anode to cathode (R x 100 scale). If SCR is shorted (zero
ohms), it must be replaced.
Measure resistance from the gate terminal to the cathode and then from the cathode to
the gate terminal (R x100 scale). If resistance reads either zero ohms (short) or infinity
ohms (open), replace the SCR. When reassembling SCRs, refer to TABLE 5.
Rectifiers (3REC, 4REC, Diode Blocks)
When checking diodes, disconnect battery and discharge capacitor 1C. When replacing
rectifiers, refer to TABLE 5. For 3REC and 4REC, disconnect one lead or flexible connec-
tion.
3REC and 4REC are diode with about 7 to 12 ohms in the conducting direction (anode to
cathode) measure on the R x 100 scale, and 10,000 ohms or higher, in the non-conducting
direction (cathode to anode) measured on the R x 10,000 scale.
Thermal Protector (TP)
Remove both the GRAY and BLACK wires from the Z plug that connects to the control
card. Read the resistance between these two wires with the VOM set on the R x 100 scale.
VOM should read 100 to 200 ohms if the 1REC heatsink is at room temperature (25C or
75F). Set the VOM to the highest ohm scale and read from each wires end to the 1REC
heatsink, reading should be infinity.