"Shoot from the hip" Electronic trouble

Report
Mass Spectrometry
Fault finding and trouble shooting
Or: Giving the bullet to those pesky
faults
Disclaimer
Mass spectrometers can cause pain
Hot soldering
irons can burn
3000 volts can kill
230 Volts can kill
Please beware that any work on the instrument
is carried out at your own risk. Isomass Scientific
cannot be held responsible for injury or damage
caused by following these techniques.
Protect your eyes
Mental pain!
Salesman’s view of solving instrument
problems
New!
Reality
• Budget shortfalls
– Not enough money to buy a new instrument
– Not enough money to pay for service
What to do
• Learn how to look after your own instrument
– Go on the manufactures training courses
– Ask questions during the installation and any visit
made by an engineer
– Regularly attend ASITA
– Read the manual and other books
– Take an electronics course
Fault Finding
• Use the instrument supplier as a resource
– The engineers are trained on the instrument
– The engineers want to help
– The engineers will have access to more
information
• Take your time
– Fault finding is not a race
– More intervention usually leads to more damage
– Take notes and pictures
Fault Finding
• Beware of dangerous voltages that might be
present in the unit under investigation
– The 230 volt supply into most units can be fatal if
touched
– Source supplies are usually at high voltage, > 3kv
• Be careful when connecting or disconnecting
meter probes
– A badly placed probe can cause a short and further
damage
• Double check connections and meter setting
before turning on the unit under test
Fault Finding
• Check power supplies first
– Fuses, check with a meter on resistance not just
visually
– If a supply voltage is less than expected it could be
that the supply is damaged or the load is pulling
the supply voltage down
– Regulated supplies should have very low a.c.
ripple
– All electronics can be seen as either a supply or
load
Fault Finding
Think before acting #1
5 minutes thought can save hours of work
Fault Finding
Think before acting #2
Think about the problem before acting
Art is a science
• Learn to draw
– Draw a block diagram of the fault area
– Write down the inputs and outputs of each block
– Make a list of possible causes
My block diagram
Power Block Diagram
A few simple techniques
• Swap
– Exchange the suspected part
• Measure
– Compared the measured parameter with the
expected value
• Observe
– Look to see what’s happening
• Write
– Keep good notes
Swap
Pirani reads atmosphere
Pirani reads 1e-3mbar
Simplify
Use a blank at point 'A' to
test the sub- system within
the instrument as a whole
Pirani showing
atmosphere after
10 minutes pumping
Voltage Measurement
Voltage Measurement
• Multimeter set to a.c. or d.c. voltage as required
– Black lead in common socket
– Red lead in V socket
• Voltage measured across one component
measures across all components in parallel
– Voltage is measured in parallel
– Circuit is powered
• Connect red probe to one lead of the component and
the black probe to the second lead
– If meter is auto-ranging note the displayed multiplier
Current Measurement
Current Measurement
• Multimeter set to a.c. or d.c. current as required
– Black lead in common socket
– Red lead in mA or A socket as required, if in doubt start in A
socket
• Multimeter must be in series with the component
– If necessary unsolder one lead from the board
– Circuit is powered
• Connect red probe to the lead of the component and the black
probe to the point the lead was previously connected to
– If meter is auto-ranging note the displayed multiplier
• Often easier to measure voltage across a resister and use V=IR
Resistance Measurement
Resistance Measurement
• Multimeter set to resistance
– Black lead in common socket
– Red lead in Ω socket
• Component must be measured in isolation
– Circuit is not powered
– If necessary unsolder one lead from the board
• Connect red probe to one lead of the resistor and the
black probe to the other lead
– If meter is auto-ranging note the displayed multiplier
Start with the obvious
If a light does not work....
Check the light bulb before dismantling the
light switch, changing the fuse in the basement etc.
Start with the obvious
If two light bulbs do not work....
Two bulbs might have blown but it's more likely that there is a
fault common to both e.g. the fuse in the basement
Fault Finding
Take good, clear notes when the instrument is working correctly
and notes during any fault finding procedure
Don't forget, "RTFM" !
Power Control
230 Volts
Control
Relay
Switched outlet
Vacuum control
Vacuum parts
Vacuum Start-up
Quick Rotary Pump Test
Penning Gauge
Turbo Pump Faults
Vacuum Service
• Rotary pump
– Change the pump oil every 6 months
• Turbo pump
– Change the oil wicks yearly
Ion Source Control
Ion Source Electronics
~4.2A
1.5mA
~4A
~800µA
~700µA
Ion source
Exploded Ion Source
Source Cleaning
Magnet Supply
Magnet Screwdriver Test
Inlets
Dual Inlet Valve Control
GC Combustion
EA
GasBench
GasBench
#140, 5700 – 1 Street S.W.,
Calgary, Alberta T2H 3A9
[email protected]
Tel: (403) 255-6631 . Fax: (403) 255-6958
Toll Free: 1-800-363-7823

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