20-622 calibration

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Below are the DR11 commands use in the 20-622 calibration procedure. The 20-622 electron gun control is used on the Physical Electronics 660 scanning auger systems.

Command Structure

Use DR11 program or RBD 147 diagnostics  for computer control.

Function                                               Command/Data (hex)

Beam Voltage                                      1ddd

Emission                                             2ddd

Objective Lens                                     3ddd

Iso. Objective Lens                              4ddd

Obj Y                                                  5ddd

Obj X                                                   6ddd

Cond Y                                               7ddd

Cond X                                                8ddd

Reset Overcurrent                                9ddd

Cond Lens                                           Addd


Notes:    – the command and the data are combined in a 16 bit word

– the left-most digit is most significant in address position and data value

– “d” represents a data value in hex

– 000H = 0, 7FFH = 2047 (mid-scale), FFFH = 4095 (max)

Set the CSR (= 1) for proper communication.


 Beam Voltage and Emission

Take the readings from the High Voltage (HV) Programming connector on the back panel. The Beam Voltage reading is taken from pin A and the Emission reading is taken from pin B. The reference is to chassis ground. Note: the bit number in () indicates the only bit set (=1), for troubleshooting purposes.

Command/Data  BV ctrl voltage (V)

1000H                                .001

1100H   (bit 8)                     .625

1200H   (bit 9)                     1.25

1400H   (bit 10)                   2.50

1800H   (bit 11)                   5.00

1C00H                               7.50

1FFFH                              10.00

Check for increasing voltage as you enter the following values in sequence: 1000H, 100FH (bits 0-3), 1010H (bit 4), 1020H (bit 5), 1040H (bit 6), 1080H (bit 7).

Command/Data  Emission ctrl voltage (V)

2000H                                 .001

2100H   (bit 8)                      .625

2200H   (bit 9)                      1.25

2400H   (bit 10)                    2.50

2800H   (bit 11)                    5.00

2C00H                                7.50

2FFFH                               10.00

Check for increasing voltage as you enter the following values in sequence: 2000H, 200FH (bits 0-3), 2010H (bit 4), 2020H (bit 5), 2040H (bit 6), 2080H (bit 7).

Condenser and Objective Lenses

A 200 ohm 2W 10-turn potentiometer must be connected to the Objective Fine Adjustment connector on the back before checking the voltages (Unless it is connected in the electronics bay) . Connect pin D to the pot wiper and connect pins A and C to the pot limits (either order). Set the pot to midway (5 turns for a 10-turn pot).

Note: the bit number in () indicates the only bit set (=1), for troubleshooting purposes. The voltages across the resistors (RX) are taken behind the front panel.

Iso. Objective

 Command/Data  R1-R6 Voltage (V)

4000H                                .016

4100H   (bit 8)                     .304

4200H   (bit 9)                      .610

4400H   (bit 10)                    1.22

4600H                                 1.83

4800H   (bit 11)                     2.44

4A00H                                 3.05

4C00H                                 3.66

4F00H                                 4.58

4FFFH                                 4.88

Check for increasing voltage as you enter the following values in sequence: 4000H, 400FH (bits 0-3), 4010H (bit 4), 4020H (bit 5), 4040H (bit 6), 4080H (bit 7).


Command/Data  R7-R10 Voltage (V)

3000H                                 .021

3100H   (bit 8)                     .322

3200H   (bit 9)                     .645

3400H   (bit 10)                   1.29

3600H                                1.94

3800H   (bit 11)                   2.58

3A00H                               3.23

3C00H                               3.88

3F00H                               4.85

3FFFH                              5.17

Check for increasing voltage as you enter the following values in sequence: 3000H, 300FH (bits 0-3), 3010H (bit 4), 3020H (bit 5), 3040H (bit 6), 3080H (bit 7).


Command/Data  R11-R14 Voltage (V)

A000H                                 .018

A100H (bit 8)                       .469

A200H   (bit 9)                     .939

A400H   (bit 10)                   1.88

A600H                                 2.82

A800H   (bit 11)                     3.76

AA00H                                  4.70

AC00H                                  5.64

AF00H                                  7.05

AFFFH                                  7.50

Check for increasing voltage as you enter the following values in sequence: A000H, A00FH (bits 0-3), A010H (bit 4), A020H (bit 5), A040H (bit 6), A080H (bit 7).


Check for proper centering of the voltages at the Objective and Condenser Steering connector on the back panel.

Command/Data  Between pins, Voltage (V)

57FFH                                   F&H, 0V +/- .4V                  Obj. Y

67FFH                                   E&G, 0V +/- .4V                  Obj. X

77FFH                                   B&D, 0V +/- .4V                  Cond. Y

87FFH                                   A&C, 0V +/- .4V                  Cond. X


20-622 System Test

It is possible for a 20-620 or 20-622 to work on the bench but not focus properly on a system. That is because on the bench the Objective and ISO Objective supplies are tested separately but on the system the objective coil is actually two coils which are tied together. So one of the objective supplies may cave in when connected to the objective coil. You can do a quick test by measuring the voltage across the current resistors behind the front panel of the 20-622 or 20-620.

Voltages for the 20-622 are listed below. The 20-620 should show a similar trend.

20-622   3kV Beam voltage, COND set to 35%, OBJ set to 74.49%, and Objective fine pot set to midrange.

COND .856
OBJ 3.68
ISO OBJ 3.69


20-622   5kV Beam voltage, COND set to 35%, OBJ set to 83.49%, and Objective fine pot set to midrange.

COND 1.076
OBJ 3.85
ISO OBJ 3.47




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