When isolating faultsin the strobe light system,first determine if the faults is in the flash tube or power supply. Replacing of the flash tube will confirm if the faults is in the flash tube or the power supply. Replacement
of the flash tube will confirm if the tube is defective. A normal operatingpower supply will emit an audible tone of 1 to 1.5 kHz. If no sound is emitted, check system using the following instructions:
NOTE: When isolating faults in the system, use schematic 33-45-01 in PA-42-720 (Advanced Trainer) Wiring DiagramManual.
(1.) Ensure input voltage at power supply is 28 volts.
POWER SUPPLY INPUT CONNECTIONS,DO NOT REVERSE CONNECTIONS.REVERSED POLARITYOF INPUT VOLTAGEWILL PERMANENTLY DAMAGETHE POWERSUPPLY,DESTROYINGA PROTECTIVEDIODE,WHICH CAUSES OVERHEATING OF THE SUPPLY. THIS DAMAGE IS NOT ALWAYS IMMEDIATELY APPARENT,BUTWILL CAUSE SYSTEM FAILURE.
CAUTION: WHEN CONNECTING/DISCONNECTING
WHENDISCONNECTINGPOWERSUPPLY,ALLOWFIVEMINUTES BLEEDDOWN TIME BEFORE HANDLING THE UNIT.
(2.) Check for malfunction in interconnecting cables.
cable are not reversed. (b.) Using an ohmmeter, checkcontinuity pins1 and 2 of interconnecting (a.) Ensure pins 1 and 3 of interconnecting
between cable. Ifa reading is obtained on the meter, the cable is shorted and must be replaced.
NOTE:A short described in steps (1.) and (2.) will not cause permanent damageto thepower supply, but the system will be inoperative. Avoid any connection betweenpins 1 and 3 of interconnecting the
cable which discharges condenserin the power supply and destroysthetrigger circuit.
EFFECTIVITY:
040-999
33-40-00
Jan10/90
PIPERAIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCEMANUAL
A. Exterior (continued)
2. WingTip StrobeLights (continued)
(e) Fault Isolation(WingTip StrobeLights) (continued)
(3.) Checkinterconnectingcablesfor shorts as follows:
(a.) Disconnectoutputcablesfrom power supplyoutlets. (b.) Check for continuitybetweenconnectorsof each interconnectingcableby checking frompin 1 to pin1, pin 2 to pin 2, and pin 3 to pin 3. When makingchecks,if no continuityexiststhe cable is broken and mustbe replaced.
(c.) Check for shortsbetweenpins 1 and 2, pins 1and 3, pins 2 and3 of the interconnectingcable. If continuity existsbetweenanyof these connections,the cable is shortedand mustbe replaced.
(d.) Check for shortsfrompins 1, 2, and 3 to aircraft ground. (Pin2 is aircraftground in powersupply.)
(f) Characteristicsof an XenonFlashTube
(1.) A xenon flashtube canbe photo-sensitiveandsomecouldbecomemoredifficultto fire
whensubjectedto darkness. (2.) Xenonflash tubesbecomeharderto fire with age or when exposedto high temperatures. (3.) A hard firing tubesometimesfireswith an enginerunning,but will notfire underlow
battery conditions. (4.) Underhot andcold cycling,during normal operation,egg shelling of the glassenvelope canoccur,or leakscandevelopin the glassseal. (5.) Xenonflashtube canself-ionize(continuouslyglowinga light blue),renderingthe system inoperative.
NOTE: All the aboveconditionsrequirereplacement.
(6.) Installationof one newtube sometimescausesthe othertube to misfire or skip, indicatingthe endof its service lifeand replacementis necessary.
(7.) A fully functionaltube shouldfire on a reducedvoltageof 10 volts in a 14V system or 22 volts in a 28V system.
EFFECTIVITY: 040-999
PAGE 4 33-40-00
Jan 10/90
PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL
A. Exterior (continued)
3. WingInspectionLight
(a) Descriptionand Operation
The lightis mountedin the leftoutboardedgeof the leftnacelle,abovethe leadingedgeof the
wing. it is a sealedbeam, 24-voltunit,controlledfroma rockertypeswitch mountedin the
overheadswitchpanel. Thelight ispositionedin the nacelleto illuminatethe leadingedge of
the wingwhenthe switchis activatedin the cockpit.
(b)
Servicingof WingInspectionLight
Servicerequiredfor this unitconsistsof replacinga burnedout lampwith a newlamp,P/N 4593.
(c)
Removalof WingInspectionLight
(1.) Be sure switchisin the OFFposition. (2.) Removenacellesideaccesspanelwherelampassemblyis mounted. Disconnectwire connectionson the backof lamp. (3.) Removefourclips holdinglampto panel. Removelamp.
(d)
Installationof WingInspectionLight
(1.) Positiongasketandlampon panel.
(2.) Installfourclips. Securewith screwsandnuts.
(3.) Connectelectricalleadsto backof lampassembly.
(4.) Positionentirepanelon nacelleside. Securewith screws.
(5.) Activateswitchin cockpitto checklampoperation.
EFFECTIVITY:
040-999
33-40-00 Jan
Jan 10/90
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