HPQ2-IP SP101009.102 – 10 October 2012
MKS Instruments, Spectra Products
29
All pins should show open circuit to all other pins EXCEPT pin 4 to pin 8, pin 4 to pin
10 and pin 8 to pin 10 which should show short as these are the filament
connections (see the next section). If any of the pins do show short to an other pin
contact your local service centre with the results of your testing and they will advise
you as to how to proceed.
7.6 Checking Filaments
If you suspect a blown filament, for instance the control unit shows filament fail,
carry out the following test before removing the analyser from the vacuum system.
1. Connect meter lead one to analyser feedthrough pin 8 which is the common
connection to both the filaments.
2. Connect the second meter lead to pin 4 (Filament 1). You should have a short
circuit, the resistance of the filament is about 0.5 ohms when it is cold.
3. Now connect the second meter lead to pin 10 (Filament 2) again your meter
should indicate a short circuit.
If either or both filaments are blown the meter will indicate an open circuit and the
filaments should be replaced.
If the meter reading suggests that the filament is good but the control unit shows a
filament fail the most likely cause would be a break down in electrical continuity.
Examine the RF/analyser connector on the front of the HPQ2-IP control unit, check
that none of the gold sockets are pushed out of place.
7.7 Changing Filaments
The HPQ2-IP quadrupole analyser is fitted with a dual, self-aligning filament
assembly. This assembly consists of a circular plate fitted with three small
feedthroughs. Between these feedthroughs on the under side of the filament plate
are attached the filament wires. When we talk about filaments and replacement
filaments it is this assembly to which we are referring. Changing filaments is
probably the most common maintenance procedure that has to be undertaken with
quadrupole analysers but the analyser has been designed to make the task as quick
and easy as possible.