20-040 X-ray source power supply LOCAL REMOTE switch

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The 20-040 X-ray source power supply is used on some of the older PHI X-ray photoelectron spectroscopy (XPS) systems. There is a switch on the back of the 20-040 that needs to be set to the LOCAL position. When in the LOCAL position the high voltage is set by the user but the 32-095 or 32-096 X-ray source control turns the 20-040 high voltage on and off. Sometimes the LOCAL / REMOTE switch can become oxidized in which case the 20-040 high voltage may not turn on. This post explains how to remove the LOCAL / REMOTE switch and hard wire the board to the LOCAL position.

20-040 front panel
20-040 front panel

Make sure that the 20-040 main power switch is OFF and then unplug all cables from the back of the 20-040 and remove the 20-040 from the electronics console.

Remove the top cover (8 cross head screws).

Unscrew the nut on the LOCAL / REMOTE switch and also unscrew the two nuts on the 15 pin connector. Unplug the 3 pin connector on the top of the board, the larger bottom connector can stay attached.

On the back of the little board that the LOCAL / REMOTE switch is attached to you can see where the switch is soldered to the board. Un-solder and remove the switch. A solder sucker works well but you can also use some solder wick.

Solder some jumper wires between the pins as shown in the image below.

20-040 board with jumpers installed

Reattach the 3 pin connector and then insert the 15 pin connector back into the slot and use the two nuts to attach the board to the back chassis. I also added a plastic screw and nut to block the hole that remains after removing the switch. You can also just leave that hole open.

Plastic nut
Hole plugged

Replace the cover and tighten the 8 cover screws.

Make sure that the 20-040 main power switch is still OFF and then insert the 20-040 back into the electronics console and reattach all the cables to the back of the 20-040.

Below is a table that shows the pin outs on the control cable that goes between the 32-095/6 and the 20-040.

Removing the LOCAL / REMOTE switch eliminates the switch as a cause of lack of high voltage with the 20-040. If your 20-040 does not work and can’t be repaired, then RBD Instruments provides a drop in replacement, the 20-042.


32-095 and 32-096 X-ray source control faulty capacitor – urgent!

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Recently, I have seen the same problem on several 32-095 and 32-096 X-ray source controls which are used on older Physical Electronics PHI X-ray photo electron spectroscopy systems.

The issue is that C9, a 680 uF electrolytic capacitor blows out and the electrolytic material leaks out on the board.  Left unattended, the electrolytic etches and oxidizes the traces on the board.

If you have an older PHI XPS system that uses a 32-095 or 32-095 X-ray source control you should pull if out of the rack, remove the cover and inspect the board immediately.

If corrosion is present, then remove the board and remove C9.  Note the polarity of C9 as the + indicator on the board may be etched away.  Then, carefully clean the corrosion from the board as best as you can.   If in the shop I use some Alconox and let it sit on the board for a while, then rinse with DI water and let the board dry overnight.   In the field I have used isopropanol or methanol and cotton swabs.    Note that if the traces are corroded badly then they may come off the board as you clean it.  If so, you will need to use some fine copper wire to rebuild the traces.

Once the board is clean and dry, replace C9 with a new one.  I will dig into this issue some more and try to determine why this problem occurs so often and come up with a permanent solution.  In the meantime, I would recommend that the C9 capacitor be replaced every 5 years.

The pictures below show where C9 is located on the control board and what the corrosion looks like.

C9 removed
C9 location
C9 Neg towards connector

XPS analyzer control non-linearity problem

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The 80-360 and 80-365/366 analyzer controls provide all the voltages to the 10-360 spherical capacitor analyzer that is used on many PHI (Physical Electronics) XPS systems.

80-365 boards Retard board is third from left

The retard voltage is used to slow down electrons and is essentially the sweep voltage.  In conjunction with the pass energy supply, the retard voltage controls the energy of the electrons that are being passed through the analyzer and into the electron multiplier and counting circuitry.

I recently had an interesting problem with a retard board on an 80-360 analyzer controller.  The issue was that the retard board output voltage was not linear.   Part of the calibration procedure for the retard board is to test the voltage at 11 specific voltages ranging from 253.6 volts to 1253.6 volts in increments of 100 volts.  This is a convenient way to confirm that the retard supply is linear.  The table below shows the hex commands that are used to set the voltages and the expected results.

In this particular case, the output voltages were close to correct at some points, but way off at other points as shown below. This non-linearity would present itself as inconsistent peak widths in the data as a function of kinetic energy.

These results at first glance look like a bit problem.  That is, the digital to analog convertor (DAC) voltages are likely off.  The DAC used in the retard board circuit is a 16 bit DAC and the output voltages should follow the voltages listed  below.

DAC Voltages

However, the DAC voltages were fine.  The retard voltage circuit comprises the DAC which drives a precision operational amplifier that in turn drives a high voltage switching supply.  Some precision high voltage resistors are  used to provide feedback.  The next most likely component that might be non-linear was the OP07 ultra-low offset operational amplifier (op amp).  The OP07 was replaced but did not solve the problem.

The next most likely cause of the non-linearity problem was the feedback resistors.  There is a total of 5 of these SX3730 5 watt wire wound high precision axial resistors in series.  To accurately measure those resistors, you need to lift one end off the circuit board.  Using my Fluke multimeter, I tested the resistance of each resistor and they all checked out as OK.  Ideally you will see very close to 1.0 megohms, but it might be off by .05 megohms. When a resistor is bad it will be open or be off by as much as .5 megohms. So, it seemed that the feedback resistors were OK as well.

That left not much in the circuit other than a few potentiometers. After spending some more time retesting all the components, I came to the conclusion that it had to be one of those feedback resistors. 

To test that theory I removed all 5 of the SX3730 1 megohm feedback resistors and replaced them with a single 5 meg ohm resistor.  And that worked!   So now I knew for sure that one of those 5 feedback resistors was the problem.  I measured the resistance of each resistor, and they looked OK.  But then I realized that the non-linearity is a function of the voltage applied to the resistor. At some voltages the resistance was OK, but at other voltages the resistance was off. 

I then decided to measure the resistance value again using a megohmmeter.  The model that I used was a Protek DI-2000M.  This megohmmeter (also called an insulation tester) puts 500 V across the resistor when measuring the resistance. I hoped that by putting 500V across the resistor that I would be able to see a greater difference in the resistance values. And that worked out as expected.  One of the resistors showed only 965 Kohms with the megohmmeter and 995 Kohms with the Fluke. I replaced that resistor and the calibration was perfect.  😊

In hindsight, duh. Since the gain of the circuit was changing as a function of the non-linearity of one resistor, the lesson is that when checking the resistance of suspected non-linear resistors, always use a megohmmeter since that will put much more voltage across the resistor than what a normal DVM will put out. Better yet, if possible, use the highest voltage that the resistor is rated for.

If your 80-360 or 80-365/366 analyzer control is not functioning properly and you need some help, please contact RBD Instruments for assistance as needed.