Advertisement
CONTROL CIRCUITRY (continued)
ANY INTERRUPTION of the control circuit will disable K1 and open the AC circuit to the rectifier. In
addition to the above lamphead interlock switches, thermal switch TS1, mounted to the rectifier heat
sink, will open and disable K1 if the temperature at the heat sinks exceeds 190° F. (88° C.). The TS1
switch will automatically re-set when temperatures fall to safe levels.
POWER CONVERSION PROBLEMS
RECTIFICATION (AC to DC) is performed by bridge diodes CR1 - CR6. CR1, CR2, and CR3 are forward
diodes, and CR4, CR5, and CR6 are reverse diodes. The two types are not interchangeable.
AN OPEN DIODE will cause a pronounced flicker in the light output. Two or more open diodes will
disable bulb ignition. A shorted diode will trip the circuit breaker protecting the AC input line. See the
following DIODE TESTING & REPLACEMENT section.
BANKED CAN CAPACITORS C1A & C1B filter the rectified DC output. C1A and C1B capacitors also
store energy to contribute to the open circuit ignition discharge.
AC circuit breaker.
RELAY K2, in the presence of high DC open circuit voltage, will pull and place Resistor R2 in
series with Capacitors C1 and C2.
C1A & C1B to promote bulb ignition. If K2 relay fails, ignition may become erratic, and R2 may remain
in circuit. With R2 in circuit, ripple will increase to a level noticeable in light output, but not necessar-
ily enough to trip the AC line circuit breaker.
DIODE TESTING & REPLACEMENT
1. Disconnect the diode from its circuit. Inspect for discoloration, oxidation, or loose crimp at lead
junction.
2. A "shorted" diode will show low resistance in both directions. An "open" diode will have infinite
resistance in both directions. An Ohmmeter test is required.
3. a) Analog VOM: Select R x 1 Ohm scale. With meter leads connected in one direction, the
reading should be zero (or nearly so); reversing the meter leads should show very high resis-
tance. If the diode does not exhibit these characteristics, replace it. NOTE DIODE TYPE: forward
or reverse.
b) Digital VOM: Select "Diode Test." With meter leads connected in one direction, the reading
should be "OL" (overload); reversing the meter leads should display approximately .4 volt.
If the diode does not exhibit these characteristics, replace it. NOTE DIODE TYPE: forward or reverse.
4. Carefully clean the area of the heat sink in which the diode mounts. Apply heat sink compound
(Radio Shack #276-1373 or equivalent) using a wood or plastic spatula or stick. A thin layer is
adequate.
5. Install the new diode and tighten securely for maximum mechanical contact and electrical con-
duction. Clean and firmly secure the lead terminal to the buss.
16
This resistor limits the inrush surge and prolongs the discharge of
WARNING
HEAT SINK COMPOUND IS HIGHLY CAUSTIC.
Do not apply with fingers; keep away from
eyes. Carefully follow ALL the instructions
printed on the package.
A shorted capacitor can trip the
Advertisement
