Piper Navajo PA-31 Service Manual page 769

PIPER NAVAJO SERVICE MANUAL
When troubleshooting the strobe light system. it must first be determined whether the trouble is in the
flash tube or the power supply. Replacement of the flash tube will confirm whether the trouble is in the flash
tube or the power supply. Replacement of the flash tube will confirm whether the tube is defective. A normal
operating power supply will emit an audible tone of I to 1.5 KHz. If there is no sound emitted, check the system
according to the following instructions. When troubleshooting the system, utilize the appropriate electrical
schematic in this manual.
a. Ascertain the input voltage at the power supply is 28-volts.
CAUTION
When
disconnecting
and connecting
power supply input
connections, do not get the connection reversed. Reversed polarity
of the input voltage for just an instant will permanently damage the
power supply. The reversed polarity destroys a protective diode in
the power supply, causing self-destruction from overheating of the
power supply. This damage is sometimes not immediately apparent,
but will cause failure of the system in time.
CAUTION
When disconnecting the power supply, allow five minutes of bleed
down time before handling the unit.
b.
Check for malfunction in interconnecting cables.
1. Ascertain pins I and 3 of interconnecting cable are not reversed.
2.
Using an ohmmeter,
check continuity
between pins I and 3 of interconnecting
cable. If a reading is obtained on the meter. the cable is shorted and should be replaced along with the power
supply.
NOTE
A fault of the type described in step I will not cause permanent
damage to the power supply but the system will be inoperative if
such a short exists. Avoid any connection between pins I and 3 of
interconnecting cable, as in step 2. this will discharge the condenser
in the power supply and destroy the trigger circuit.
c. Check interconnecting cables for shorts.
1. Disconnect the output cables from the power supply outlets.
2. The following continuity checks can be made with an ohmmeter.
3. Check for continuity between the
connectors of each interconnecting
cable by
checking from pin I to pin 1, pin 2 to pin 2 and pin 3 to pin 3. When making these checks,
if no continuity exists the cable is broken and should be replaced.
4.
Check continuity
between pins
I and
2. 1 and
3 and
2 and 3 of the
interconnecting
cable.
If continuity
exists between
any of these connections,
the cable is
shorted and should be replaced. (Refer to b-2 above.)
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