990 CLD Autoline™ Leak Detector
DR
AFT 2/2/04
4-13
4. Set the FILAMENT switch to the ON position to energize the spectrometer tube filament
and verify that the green FILAMENT indicator is lit.
5. Adjust R58 counterclockwise very slowly until the FILAMENT indicator turns off.
This turns off the ion source filament whenever the spectrometer tube pressure rises
above the top of the green band (0.25 milliTorr).
6. With a voltmeter attached to the general connector I/O pins 5 (+) and 6 (-), adjust R19
on the I/O PCB assembly in the rear of the unit for 4 V on the meter
.
7. Replace the safety shield on the main electronics and replace the cover when servicing
adjustments are completed.
8. Ensure to set the MAIN POWER switch to OFF. Remove the 50 MOhm resistor from the
SHV connector.
Amplifier Offset Adjustment
There are four amplifiers associated with the spectrometer tube and the leak rate display: a
preamplifier module in the spectrometer tube body and three amplifiers in the controller. If
the amplifiers require re-zeroing.
To re-zero amplifier offset:
1. Make certain that connectors JMP 1 and JMP 2 on the upper right-hand corner of the
I/O Control Board (the smaller of the two boards at the back of the Controller) have
jumpers across their upper two pins.
Make certain that connector J1 on the I/O Control Board (on the left side in the center of
the board) has jumpers across pins A and 1.
2. With the power shut off, remove the preamp connector on the rear panel of the
Controller.
3. Short together pins 8, 14, and 15 on the preamp connector mounted on the rear of the
Controller.
4. Connect a mV meter to the LEAK RATE pins GENERAL 110 connector.
5. Disconnect the plug from J3 on the soldered
side of the display PCB and turn on the
Controller.
6. Adjust R22 on the 110 Control Board until the mV meter reads 0 V ± 0.5 mV.
7. With the bargraph set to the most sensitive scale, adjust R77 on the display PCB so that
1 bar is lighted on the bargraph, then remove the shorts on the preamp connector, and
reconnect the plug to J3.
8. Calibrate the leak detector as described in “Calibrating the Leak Detector”.
9. Replace the safety shield and the top metal cover on the Controller.
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