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.
Calibration
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).
Objective
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).
Condenser
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).
Steering
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 |
20-622 Coil voltage supply test points
There are three coil voltage supplies in the 20-622:
Condenser 30V DC
Objective 34.5V DC
Isolated Objective 40V DC
To measure the supplies, remove the 4 screws on the 20-622 front panel and drop the front panel down (it is on a hinge).
There are three fuses visible on the front center of the heat sink assembly.
The top fuse is the Condenser supply, and it has a value of 1.5A slow blow. Measure from either side of the fuse to the chassis and there should be approximately 30 V DC when the 20-622 main power is turned ON.
The center fuse is the Objective supply, and it has a value of 2A slow blow. Measure from either side of the fuse to the chassis and there should be approximately 34.5 V DC when the 20-622 main power is turned ON.
The bottom fuse is the isolated Objective supply, and it has a value of 2.5A slow blow. Measure from either side of the fuse to the ISO Objective test point (white wire) near the far-right hand current sense resistors. There be approximately 40 V DC when the 20-622 main power is turned ON.
The picture below shows the ISO Objective test point location.
