971B UniMag™
35
Operation manual
N: 970B-ANO
Service and Repair
When a Cold Cathode sensor is turned on and operated at pressures higher than 1.0E-3 Torr, the inside wall
of the ionization chamber can be sputtered by ions formed by the high energetic plasma. Inert gases like
argon are easier to ionize and consequently the sputter effect is more significant in such environment.
If the transducer is contaminated, the pressure measurement will typical be lower than actual pressure.
Sputtering can also be visually detected since the inside wall of the transducer changes color. When
operated in oil lubricated pumping systems, hydrocarbons can cause contamination of cold cathode
measuring cell. The cold cathode hour counter and pressure dose can be used to determine if service is
required. (See page 20.)
If sputtering or contamination occurs, the ionization cell kit or anode module can be changed from the
flanges side without disassembling the transducer electronics. The anode module (p/n: 970B-ANODE-FE
(1)
)
and cell kit (p/n: 970B-CELLKIT) is available as spare parts. The basic accuracy of the cold cathode sensor
can change after replacement of anode. The cell kit and anode module can also be cleaned by mechanical
polishing.
P/
DE-FE
(1)
P/N: 970B-CELLKIT
Do not touch cell kit, anode module, screen,
screws or clip ring by hand. If items are
accidental touched by hand, use alcohol to
clean items.
Changing the Cell kit
1. Turn power off and remove cable.
2. Dismount the transducer from the vacuum system.
3. Remove the clip ring (1) using a clip ring remove/insert
tool (p/n: 100017193).
4. Remove the screen (2).
5. Unscrew the Torx (T6) screws (3) at the rear screen (4).
6. Remove the rear screen (4).
7. Insert the new screen (Do not touch by hand).
8. Insert the Torx (T6) screw (3) and tighten.
9. Insert the front screen (2) and clip ring (1).
Changing the Anode
1. Remove cell kit point 1-6
2. Unscrew the 3 screws at the anode module.
3. Remove the anode module and clean module or insert new.
4. Insert the anode module screw and DO NOT tighten. After all screws are inserted carefully tighten
the screw a little and move on to the next one. Continue to tighten the screws one by one until all
tight.
5. Perform leak testing of the transducer.
6. Insert cell kit point 7-9.
Cleaning anode module and screens
Contaminated parts can be cleaned by mechanical polishing or ultrasonically cleaned followed by alcohol
degreasing. Make sure that all parts are clean and remove any discoloring of the stainless steel and titanium
parts. Alternatively, the anode module or screens can be replaced with new parts
.
(1)
For units with S/N: 1202347357 and lower use P/N: 970B-ANODE