XPS analyzer control non-linearity problem

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.

80-365 analyzer control notes

This blog post is a compilation of notes which are helpful when troubleshooting or calibrating the 80-365 (and 80-366) SCA analyzer control.

The 80-365 SCA analyzer control provides all of the voltages to the SCA (spherical capacitive analyzer) used on older PHI XPS (X-ray photoelectron spectroscopy) systems. Those include the retard voltage, the pass energy, the lens voltages and the electron multiplier voltage.

To troubleshoot or calibrate the 80-365, follow the calibration procedure in the 80-365 manual. Note that high voltages are present on the 80-365 boards, always refer these types of measurements to technicians who have been properly trained in working with high voltage!

If are unable to repair the 80-365 yourself, please contact RBD Instruments and we can repair the boards for you.

80-365/66 Lens Board DAC bit test

To test individual bits:  Write out on DR11 A CSR 1   

Note:   Write the low order byte out first, then the high order byte. If you get out of sequence you need to turn off the card rack power to reset the board and start over.

Lens 2

Measure from the left side of R62 to the right side of R94/G4

BitLow byteHigh byteDAC voltage

Lens 3

Measure from the right side of R70 to the right side of R94/G4

BitLow byteHigh byteDAC voltage

80-365 Lens board calibration notes

For XPS and AES, the output voltages are positive, and the fine supplies are negative.  Make sure that you set the polarity before programming on dual polarity boards.

1310 is + polarity for L3

1320 is + polarity for L2

Common data values

L2            Output C53/G5                  Fine Supply    – lead ground side R143   + lead right side R142/G5

1801,1800 – Adjust R45/A3 for -20V on fine supply

1800, 1808 – Adjust R77/B4 for – 20V on fine supply           Adjust R67/G3 for +409.6V on C53

18D4, 1830 – Adjust R67/G3 for +2500.0 V on C 53 output.  Readjust R77/B4 for -20V on fine supply

1800, 1800 – zero

L3            Output C41/E5                   Fine supply         – lead ground side R127/E5  + lead left side R120/E5

1601, 1600 – Adjust R52/C3 for -20V on fine supply

1600,1608 – Adjust R87/D4 for–20V on fine supply      Adjust R59/E3 for +409.6V on C41

16D4, 1630 – Adjust R59/E3 for +2500.0V on C 41 output. Readjust R87/D4 for -20V on fine supply

1600,1600 – Zero

NOTE:    If you have issues with the +5V supply dropping and voltages not loading properly, look at the local power supply board.  You may need to replace the 3524 regulator on the local power supply board.

80-365/66 Pass Energy board DAC bit test

To test individual bits:

Pass energy range = is 0 to 10V on the DAC = 1920 or 2145 depending on the model number of your analyzer control.

Write out on DR11 A CSR 1   

Note:  Write the low order byte out first, then the high order byte. If you get out of sequence you need to turn off the card rack power to reset the board and start over.

To set the DAC back to zero between bits, write out 1a00 twice

The following table shows the voltage on the DAC measured from TP24 / C2 to TP24B /C2  

0000 0000 0000 0001

bit 0

0.022 V

1a01, 1a00 = .0001525 V on the DAC

0000 00000000 0010

bit 1

.044 V

1a02, 1a00 = .0003052 V on DAC

00000 0000 000 0100

bit 2

.088 V

1a04, 1a00 = .000 6V on DAC

0000 0000 0000 1000

bit 3

.019 V

1a08, 1a00 = .00122 V on DAC

0000 0000 0001 0000

bit 4

0.35 V

1a10, 1a00 = .00244 V on DAC

0000 0000 0010 0000

bit 5

0.7 V

1a20, 1a00 =.00488 V on DAC

0000 0000 0100 0000

bit 6

1.4 V

1a40, 1a00 = .0097 V on DAC

0000 0000 1000 0000

bit 7

2.8 V

1a80, 1a00 =.019 V on DAC

0000 0001 0000 0000

bit 8

5.63 V

1a00, 1a01  =.039 V on DAC

0000 0010 0000 0000

bit 9

11.25 V

1a00 ,1a02  = .078 V on DAC

0000 0100 0000 0000

bit 10

22.5 V

1a00 ,1a04  = .156 V on DAC

0000 1000 0000 0000

bit 11

45 V

1a00 ,1a08   = .3125 V on DAC

0001 0000 0000 0000

bit 12

90.02 V

1a00 ,1a10  = .625 V on DAC

0010 0000 0000 0000

bit 13

180.03 V

1a00,1a20   =1.25 V on DAC

0100 0000 0000 0000

bit 14

360.06 V

1a00 ,1a40   = 2.5 V on DAC

1000 0000 0000 0000

bit 15

720.13 V

1a00 ,1a80  = 5.0 V on DAC

All Bits:

1A00, ,1aFF   = 10 V on DAC

1920 or 2145 VDC on the output across C56

80-365 / 366 Pass energy board range note

The 80-365 and 80-366 pass energies have different maximums.

The 80-365 is 1920V

The 80-366 is 2145V

Make sure that you have the correct procedure when you calibrate the board.

Measuring the Pass Energy output voltages

There are some scale factors involved when measuring the pass energy voltages.   

If you are measuring the pass energy voltage across C56 on the pass energy board, the scale factor is approximately X 1.34.  For example, if you set the pass energy to 187.85, the output voltage across C56 is 187.85 X 1.34 = 251.8 VDC.   You can calculate any pass energy actual voltage value by multiplying the pass energy in the software (set up an alignment or survey) by 1.34.

If you are measuring the test points in the filter box, the scale factor is to divide by 1.7.    For example, a pass energy of 187.5 divided by 1.7 = 110.3 VDC.  If you set up the pass energy to 187.5 in the software, you will see approximately 110.3 VDC between the IC and OC test points in the filter box. The resistors in the filter box divide the voltages so that they are correct on the IC, OC and MR contacts in the analyzer.

To summarize –

C56 output on pass energy board = Pass Energy X 1.34

Test points in filter box = Pass Energy divided by 1.7

80-365 Local Power supply board notes

Capacitor Voltage Comments
C33 22V +/1 1.5V   adjust R27 Transformer output before regulator
C35 +15 Pass energy board power
C36 -15 Pass energy board power
C34 +5V Pass energy board power
C9 22V +/1 1.5V  adjust R3 Transformer output before regulator
C10 +15 Lens board power
C7 -15V Lens board power
C12 +5V Lens board power
CR35 cathode to CR36 anode +225V Pass energy board power
CR 37 anode to CR36 anode -225V Pass energy board power
CR17 cathode to CR17 anode +150V
CR18 anode to CR17 anode -150

TIP: If the voltages are low when the pass energy or lens boards are installed, most likely the issue is a weak 3524 regulator. Replace it with a new SG3524N

80-365 Retard supply bytes

bitlow byte (hex) hi byte (hex)DAC V

80-365 Lens Board Single Polarity modification

The dual polarity lens board high voltage switching relays can breakdown at voltages above 1kV and cause a variety of intermittent problems.   Since most systems do not use the negative polarity, removing the high voltage switching relays and converting the lens board to a the single (positive) polarity can solve the breakdown problem and make the board more reliable.

Modification Procedure:

  1. Remove the red cover (3 screws) that shields the high voltage components.
  2. Unsolder and remove the two Kilovac high voltage relays (K1, K2)
  3. Jumper the relays as shown in the pictures below.
  • Solder a jumper on the back of the board on IC 22 between pins 2 and 3.
  • Solder a jumper on the back of the board on IC 21 pins 6 and 7.
  • Remove ICs U13, U21 and U22 (Note that some boards do not have sockets in which case you need to un-solder the ICs before putting the jumper in).
  • Cover the open sockets on U13, U21 and U22 with electrical tape.  That will make it easier if the board ever needs to be repaired again as it will indicate that those IC sockets are not used.
  • Check the Single Polarity box on the upper left-hand side of the board.

You can also remove these components as they are no longer used –

R54 (pot) 1k ohm


R67 (pot) 1k ohm


Q1, Q2  2N3704

Q10, Q10A    2N3725