Electronics Trouble-Shooting Secret Weapon

The other day I was working on a particularly difficult electronics problem with an ion gun controller and to help figure it out, I needed to dust off my trusty Huntron Tracker. I don’t need to use it very often, but when needed, there is nothing better for troubleshooting electronics problems.

Huntron Tracker
Huntron Tracker

First introduced in 1979, the Huntron Tracker displays an analog signature, which is a combination of resistive, capacitive, inductive, and semi-conductive characteristics. This visual display is very helpful for comparing electronics components on a defective board. The Tracker is particularly useful for comparing components on a known defective electronics board with a known good one. The Tracker applies a tiny AC voltage to the probes so you can test components with no power applied to the board that you are testing.

Compare known good board components to defective board components
Compare known good board to defective board

You can usually find defective electronics components with a DVM (digital volt meter) by testing diodes and capacitors, then measuring resistance values. But there are times when all of the individual components check out as OK with a DVM, but you know that there must be at least one defective component because the board does not work properly. For those times, the Huntron Tracker works like a champ every time. By finding some components that read differently with the Tracker, you can get a clue and ultimately, find the problem. 

The early model Huntron Trackers had a little CRT display and three power level settings. Those models are still available on EBay for about $300.00. The Tracker that I use is one of these early ones and it still works well.

Over the years Huntron Trackers have evolved and today’s models include more power settings, automated testing, and software. For more info visit Huntron at –


If a new Huntron Tracker is out of your price range or you can’t find an older one, there are also inexpensive curve tracer kits available on eBay that provide Tracker functionality using an oscilloscope. To find those, go to eBay and search for Curve Tracer kit.

Curve tracer board

Research Gases for Laboratories

Laboratory gases are readily available in large cylinders from companies such as Airgas, Norco and local welding supply companies.

Large gas cylinders

But for small quantities of gases or specialty gases used in vacuum optics such as UV sources and Ion guns, it may make more fiscal sense to use lecture bottles instead of the larger size gas cylinders which are commonly found in laboratories.

Lecture bottles are small compressed gas cylinders that are typically 12-18 inches long and 2 to 3 inches in diameter.  

Lecture Bottle

They hold approximately 2 cubic feet of gas and are pressurized to as much as 1800 PSI.   High pressure gas cylinders require a regulator to step the pressure down.  The pressure required for the application will determine which regulator is needed.   For example, the Varian variable leak valve used on many 04-303 ion sources can take a maximum pressure of 500 PSI.  However, it is recommended that the argon gas pressure be set to 15 to 25 PSI for best results.    

Since lecture bottles are small, it costs less to ship them.  But most importantly, when you buy a lecture bottle you are buying the bottle as well as the gas.  Full sized cylinders are generally rented for a monthly fee in addition to the cost of the gas and delivery. Factoring in the monthly rental fee for the cylinder, a lecture bottle could be much less expensive over time. Especially for optics like UV sources where you may only use it a few times a year.

In the US, Matheson provides a wide assortment of specialty gases in lecture bottles.  Matheson also has a worldwide distribution network.




Ultra-high purity gases have 5 nines (99.999%) purity and Research grade gases have 6 nines (99.9999%) purity.   

Another provider in the US that carries Lecture bottles is Advanced Specialty Gases –


In Europe,  Messer can provide gases in small cylinders:



In the UK, CK Gas Products provides a variety of gases in lecture bottles:


Gas regulators are available from these companies as well as from Grainger. Be sure to specify the type of connection on the gas bottle when you order it and also to order the correct connection on the regulator. For best results, insert a valve between the regular and the outlet line. Finally, you also will need to pump out the line and regulator before opening the gas bottle as otherwise your gas will become contaminated with air.

Testing the fuses on the Card Rack power supply outputs

The fuse strip located near the hinge on the OEM supply door routes the +5, +15, and -15 voltages from the OEM supply to the card rack unit motherboards.

Each card rack unit has a dedicated section of fuse strip and specific fuse values.

When troubleshooting problems with card rack units it may be necessary to test the fuses in the fuse strip. With the card rack power OFF you can visually inspect each fuse to see if any of them look like they are blown. You can also use an ohmmeter to measure the resistance of the fuses (typically one ohm or less). In some cases it is helpful to measure the actual voltage on the fuses. It is possible that a fuse that looks good is actually blown. Or the voltage on the fuse may be loading down on the output side.

Since the +5, +15, and -15V OEM supply outputs are floating with respect to ground, you need to reference your meter to the correct place in order to measure the voltage. The card rack power needs to be ON when measuring the voltages on both sides of the fuses. The voltage should be very close to the same value on both sides of the fuses. One side is voltage in, the other side is voltage out to the card rack unit.

Fuses and reference points

The picture below shows the correct OEM supply reference point for the +5V, -15V, and +15V fuses.

For example, to measure the middle section -15V fuse you would need to put your DVM red lead on the left side of the middle fuse, and the black lead of your DVM to the CH3 white wires on the OEM supply. Then also measure the other side of the same fuse. The voltage on both sides of the fuse should be very close (within a few millivolts). Note that you may need to remove the protective plastic cover on the fuses in order to be able to measure the fuses.

Section number and fuse locations

There are up to 13 sections on the fuse strip and each section is typically dedicated to a particular card rack unit motherboard. Keep in mind though that the fuse locations are not written in stone and so units on your system may be plugged into other fuse sections. Also, some units are removed when an RBD software upgrade is installed. When in doubt, trace the power cables from the back of the motherboard to the fuse strip.

The fuse values (in Amps) and locations are shown below:

5400 XPS                                                                                                                                 

Section Unit Top +5V Middle -15V Bottom +15V
1 72-488 10
2 71-205 5 5 2
3 72-250 3 1 1
4 72-490 10 5 5
5 72-030 1 1 5
6 Not used      
7 Not used      
8 80-360 5 5 5
9 77-067 2 2 10
10 72-360 1 1
11 Terminator 1
12 Not used      
13 Not used      

5600 XPS

Section Unit Top +5V Middle -15V Bottom +15V
1 72-366 1 1 1
2 80-365/366 5 5 5
3 72-030 1 1 5
4 71-205 1 2 1
5 72-488 10
6 74-500 10
7 MCD Preamp 1 1
8 81-175 or 73-080 10 2 2
9 74-062 10
10 97 or 72-100 1 2 5
11 73-070 or 73-080 5 2 2
12 73-057 3 3 3
13 72-700 1 1 1

650 / 660 AES

Section Unit Top +5V Middle -15V Bottom +15V
1 79-170 or 81-175 10 2 2
2 74-062 10
3 72-150 / 96A 5 5 5
4 74-500 / Term 10 0 0
5 Not used      
6 Not used      
7 AES 72-100 / Term 3 2 5
8 97 SED / 72-100 1 2 5
9 Not used      
10 72-105 1 2 1
11 72-600 2 1 1
12 73-057 / Term 3 3 3
13 77-072 5 2 2

Here is an example: Lets say you want to measure the voltage on the 80-365 fuses on a 5600 XPS system. You would first locate the correct fuse section, in this case that is section 2. The top fuse in section 2 is the +5V supply and so you would measure from the left side of the top fuse in section 2 to the white ground wire on Channel 1 (the big lugs) on the OEM supply. Then you would also check the other side of the same fuse to make sure that you have the same voltage on both sides of the fuse. The middle fuse in section 2 is the – 15V fuse and it is referenced to the white wires on Channel 3 on the OEM supply. Finally, the bottom fuse is the +15V and it is referenced to the white wires on Channel 2 of the OEM supply.

By using the correct reference point you can easily measure the voltages on both sides of the card rack fuses when troubleshooting electronic problems with your older PHI XPS or AES system. As always, refer servicing to qualified personnel. The OEM fuse voltages are considered low voltage. However, most of the card rack units themselves generate high voltages and should be only worked on by technicians with the proper training to work safely with high voltage. If you need help troubleshooting a problem with your XPS or AES system, contact RBD Instruments for assistance.