Model SR715 Model SR720 LCR Meters

MAINETENANCEBUILT IN FIXTURECLEANINGREMOVING LEADSSeveral times a year, both the radial and axial test fixtures should be examinedfor any build up of waxy coatings from lead material. If the contacts appear dirtythey should be cleaned. To clean both fixtures, use a thick piece of paper orcardboard moistened with isopropyl alcohol or a mild cleaning solvent. Slide itback and forth between the contacts. Repeat until no further residue comes off.Allow the fixture to dry before making measurements.The radial fixture has a lead catcher on the bottom so any leads or contaminantsthat fall into the the fixture do not fall inside the unit. Cleaning this requiresremoving the top of the unit and detaching the fixture.Removing the topTurn off the power and unplug the unit from the AC power. Remove any parts oradapters from the fixture. Next remove the four screws located on the bottomcorners of the unit. Place the unit right side up on its feet and gently slide theplastic top off of the metal base. It is necessary to slide the top gradually off of thefixture and the back panel since it fits tightly. When the top is removed, stand it onits left side near the unit to avoid damaging the front panel cables. To replace thetop, reverse these steps taking care to align the top over the fixture and rearpanel. Finally, replace the four screws.After the top is removed, remove the four screws that hold the fixture mountingbracket to the PCB (printed circuit board). Use a 1/4" wrench to remove the nutsthat hold the fixture to the mounting plate. Slide the plastic lead catcher down untilthe leads can be removed. Do this to one half of the fixture at a time to eliminateconfusion. Slide the lead catcher back up to the fixture and replace the nuts.Attach the mounting bracket to the PCB and replace the top.It may be easier to completely detach the fixture from the PCB before trying toremove the lead catcher. See the section on removing the fixture and then followthe directions above for cleaning out any leads.CHANGING RADIALFIXTURE CONTACTSIf the contacts become badly worn or too dirty to clean, it is necessary to replacethem. Contact SRS for replacement contacts. Changing the contacts will involveremoving the top and detaching the fixture completely from the PCB. Thisrequires several tools and soldering ability.Tools required:3/16", 1/4" and 9/32" wrenches or nutdriversPhillips screwdriverWire cuttersSoldering iron and solderRemoving the FixtureRemove the top of the unit as described above. Detach the two ribbon cables andlugged wire from the main board. Set the lid to one side. If present, remove theGPIB/Handler option board, including the rear panel bolts. (This requires the9/32" and 3/16" wrenches for the GPIB and Handler connector.) Remove the3/16" bolts for the RS232 connector. Next remove the 12 screws holding the PCBto the chassis and the two screws on the bottom right rear of the unit. Rotate thefront of the board up so the bottom is accessible. Desolder the leads that runfrom the fixture to the board. Turn the board right side up, remove the four screwsholding the fixture mounting bracket to the PCB and lift the fixture mountingbracket off.6-5