5-2. Auto-Adjust Routines; Description - HP 8642A Operating Manual

Adjustments
Model 8642A/B
5-1. ADJUSTMENTS
If a repair is done by the "Module Exchange" method, no adjustment of the HP 8642 or the exchange
module is necessary. If a component level repair is performed on a module, it will be necessary to
do its Manual Adjustments and/or Auto-Adjust Procedures to ensure its I/O spec's.
Due to the modular nature of the HP 8642, the adjustment of a module will not effect other modules
in the instrument. After the repair of a module, it is only necessary to adjust that module. Therefore,
the adjustments have been integrated into the Troubleshooting Information in Section 8.
For example: After two years of operation you find that AM distortion performance is at the extreme
limits given in Table 1-1. After using Module Substitution (see On-Site Service Manual) to isolate the
problem to A13, you turn to the A13 tab in Section 8. You perform the AM Distortion Adjustment
followed by the A13 Auto-Adjust Routine. The AM distortion performance is now returned to
nominal.
5-2. AUTO-ADJUST ROUTINES
Description:
In the service documentation for the HP 8642 there will be references to Self-Cal, Self-Calibration,
and Auto-Adjust. These three terms refer to the same firmware routines built into the HP 8642
that are used to regenerate module correction data (sometimes refered to as Cal Data). The Cal
Data is stored in EEPROM on the A3 board and is used to control the modules during instrument
operation. A back-up copy of the Cal Data is stored in EEPROM on the A20 board,which is located
under MP 65 on the rear panel.
The Auto-Adjust routines control external measurement equipment via HP-IB for the purpose of
regenerating A2, A6, All, A12, A13, and A14 module correction data, after a component level
repair of the module. External measurement equipment required includes; a voltmeter, printer, and
HP 8902A. In some cases an HP 890IB may be substituted for the HP 8902A. The printer must
have HP-IB capability (such as an HP 2225A). The voltmeter must also have HP-IB capability; an
HP 3478, HP 3455 or HP 3456 are some voltmeters that can be used. A list of equipment needed
for each Auto-Adjust Routine is given in Table 5-1. At HP 8642 power up, default HP-IB addresses
are assumed (see Table 5-2.) If the HP-IB addresses of the external equipment are different from
the default values, use the service special functions given in Table 5-2 to re-define the addresses the
HP 8642 will use.
Table 5-1. Required Equipment for Auto-Adjust.
Module
A2
A6
A11
A12
A13
A14
HP-IB Printer
Yes
Yes
Yes
Yes
Yes
Yes
HP-IB DVM
Yes
Yes
Yes
Yes
Yes
No
HP 8902A
No
Yes or HP 8901 A/B
Yes
Yes or HP 8901A/B
Yes
Yes
Table 5-2. Changing the Default HP-IB A ddresses.
("XX" = New two digit HP-IB address.)
Instrument
Printer
HP 8901 A/B, HP 8902A
DVM
Default
HP-IB Address
01
14
23
Service Special Function
Key Sequence
81 XX Hz
82 XX Hz
83 XX Hz