Troubleshooting electronics resources

1-30-20   I updated this blog post to include a video on how to isolate a thermally unstable electronic component using a heat gun and cool spray.

When a problem develops with your XPS or AES spectrometer and you contact RBD Instruments for assistance, we frequently hear the same question – “What could be the source of the problem?”. The troubleshooting electronics tips below may help to find out.

Most problems on XPS and AES spectrometers can be broken into two broad categories – Optics problems and electronics problems. Optics (electron optics) are parts of the system that are installed on the vacuum chamber and include things like spherical capacitive analyzers, cylindrical mirror analyzers, sputter ion guns, x-ray sources, neutralizers and so on. Electronics include units such as power supplies and controllers.

Optics can generally (but not always) easily be tested by simply measuring the resistances on the electrical feedthroughs as specified in the optic’s manual. For example, a 04-303 ion gun should have contact between pins 1 and 2 (the filament) only. All other pins should be open to each other and to ground. By open, we mean that the electrical resistance is infinite. If pin 3 were shorted to ground, we would know that the objective lens inside the ion gun has a flake that is shorting it out, and the ion gun needs to be taken apart and rebuilt. But an optic component can have correct resistances and still have a problem (such as an open contact). Sometimes a short in an optic can also cause a failure in an electronic unit.

Electronic units are the source of problems with XPS and AES spectrometers more often than optics. Most of the students who use XPS and AES spectrometers in a university environment do not have enough training or experience with electronics to really dig into the electronic circuitry, but there are still a number of simple steps that can be taken that may result in a successful repair.

First of all, make sure that all power is off to any electronic unit that you work with. Measurements of voltages should always be performed by personal who have been training to work with electronic components and (often) high voltage. Potentially lethal voltages are present in these types of systems. If you are not properly trained, do not attempt to measure voltages in electronic units.

But, as long as the power is off and the unit is unplugged, you can safely visually inspect the unit and the boards inside of the unit for obvious signs of damage. For the most part, these are indicated by discoloration of the circuit boards, melted traces, melted transistors, dried up capacitors, and burnt resistors. If you find some components that are visibly damaged, then replacing them may solve the problem. Or, there may also be additional problems and the damaged components are just a symptom.

Some things to look for include:

Heat damage to a circuit board: Discoloration of the board which indicates that a component has been running very hot.

Melted components: Transistors (the plastic type) can actually melt when overheated. This is easy to spot.

Cracked capacitors: When capacitors dry out (after say 20 years or more) they can fail. See the links below for detailed instructions on how to test a capacitor. Be careful with larger value capacitors as they can hold a charge for a long time. Just to be safe, discharge capacitors before you measure them by clipping a resistor (a few hundred to a few thousand ohms is typical) across the contacts. This is not necessary for small value low voltage capacitors.

Burnt resistors: Resistors that burn up can turn to carbon and be difficult to identify without a schematic and board layout. Measure the resistance of suspect resistors with an ohmmeter. Sometimes you need to lift one end of the resistor (desolder one end of the resistor from the board) when measuring resistors in circuit as other components that may be in parallel with the resistor can affect the reading.

Shorted diodes and transistors: You can use a DVM in the diode check mode to test diodes and transistors for shorts. See the links below for detailed instructions on how to do that.

Dullness on transistor housing: If a metal housing (cover) transistor overheats often the finish on the transistor housing may be dull as a result of overheating. You can compare the finish to other similar transistors and then use a DVM in the diode check mode to test the suspected transistor. Plastic housing transistors that have melted are readily apparent.

Below I have listed some links to troubleshooting electronics resources. If you can’t fix the problem on your older Physical electronics (PHI) electronic unit yourself after following the steps in this post, we can provide you with technical support, repair services, loaners or exchange units. Contact us for more info at

 Troubleshooting Electronics resources;

How to isolate a thermal problem:

Video on how to test a diode:

Article on how to test a diode;

Video on how to test a transistor:

Article on how to test a transistor:

Video on how to test a capacitor:

Article on how to measure a capacitor:

 General troubleshooting information:



Auger Electron Spectroscopy Tutorials

RBD Instruments’ microCMA is an affordable compact Auger Electron Spectroscopy (AES) cylindrical mirror analyzer package which is small enough to add to existing vacuum chambers.  For applications which require elemental information on the top most mono layers of specimens, AES can be the perfect solution. More information…

Following are links to a variety of Auger Electron Spectroscopy tutorials which explain in detail the principles of AES, the instrumentation, and the applications.

Wellesley College AES  (pdf)

Eagle Analytical Labs AES Theory

Hong Kong City EDU AES (pdf)

University of Delaware AES (pdf)

Johns Hopkins University Principles of AES

Auger_Electron Spectroscopy (Powerpoint)

MicroCMA Sample Data (pdf)


EMO box push button switches


The EMO box (Emergency OFF) used on many PHI systems has switches that can become noisy, stick or fail to operate at all. These switches are used to turn on and off the card rack power, main electronics console power, vacuum console power, bakeout power and to turn off and reset all power.

Another very common issue is that the light bulbs in the switches tend to burn out on a yearly basis.  This blog post will describe where to get replacement parts for the EMO boxes.

The round red EMO button switch is still available but the original square push button switches that were produced by Cutler-Hammer (now Eaton) are very difficult to find. Honeywell equivalents are listed below.

There are two styles of EMO boxes.  The 32-005 style has a Bakeout switch and the other style has a Vacuum Console power switch.

EMO box
EMO box
32-005 EMO box
32-005 EMO box

Equivalent replacement switches produced by Honeywell are listed below.

EMO box switch
EMO box switch
EMO button McMaster-Carr PN 7403K42  
Main Power ON/Reset   Honeywell PN #: AML21CBA3AC
Allied Electronics Stock #: 70119090
Main Power / OFF Honeywell PN #: AML21CBA3AC
Allied Electronics Stock #: 70119090
Electronics  Console Power Honeywell PN #: AML21CBE2AD
Allied Electronics Stock #: 70119866
Vacuum Console Power Honeywell PN #: AML21CBE2AD
Allied Electronics Stock #: 70119866
Card rack power Honeywell PN #: AML21CBE2AD
Allied Electronics Stock #: 70119866
Bake Out Power Honeywell PN #: AML21CBE2AD
Allied Electronics Stock #: 70119866

Original lamp –

T1 3/4 Wedge lamp
T1 3/4 Wedge lamp

Lamp; Incandescent; T-1 3/4; Sub-Mini Wedge; 28V; 40mA; 0.3MSCP; 7000 Hrs

Manufacturer #: 85

Allied Stock #: 70013004

Recommended LED replacement lamp –

T1 3/4 LED wedge lamp
T1 3/4 LED wedge lamp

Lamp; LED; T-1 3/4; Sub-Mini Wedge; White; 28V; 40mA; 0.3MSCP; Lamp life 30,000 hours.

Manufacturer #: LED-24-T1.75 WEDGE-W Allied Stock #: 70012994

These LED lamps are more expensive but will last for almost 4 years compared to about 1 year for the regular tungsten lamps.

Mouser PN 560-LE-0509-01W is a white LED that would work for all of the switches and it costs less. Made by JKL Components

Bonus – EMO box schematics are shown below

32-005 EMO box
32-005 EMO box
EMO box
EMO box