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GPIB
4-18
BOARD
TROUBLESHOOTING PROCEDURES
The GPIB troubleshooting procedures in this section apply only to
earlier through-hole board assemblies. Surface-mount GPIB
assemblies are not repairable to the component level. If defective,
the entire GPIB assembly must be replaced.
Troubleshooting procedures for the GPIB board and Front
Panel are given in the flow chart of Figure 4-6. The
procedures first ensure that the bias voltages for the GPIB
board circuits and the Front Panel display are correct. The
microprocessor clock, the RAM, and ROM circuits are then
checked. After these preliminary checks are made, signature
analysis tests are performed as described in paragraph 4-22
to determine which component is defective.
4-19 Test Setup
The following test setup allows access to the components on
the GPIB board:
a.
Disconnect the line cord.
GPIB
b.
Remove
the
paragraphs 4-3 through 4-6.
c.
Place an insulating material on the chassis and lay
the GPIB board on top of the material.
d.
Reconnect all cables in their proper locations.
e.
Connect the line cord.
The GPIB board is connected to the chassis ground with one PC
board screw and through the GPIB connector. When checking the
GPIB board with an oscilloscope, be sure that the scope's ground
is connected only to a ground point on the GPIB board itself.
Connecting the scope ground to any other point on the GPIB
board may result in damage to the supply.
AND
FRONT
PANEL
NOTE:
board
as
described
4-20 Post Repair Calibration
If the GPIB board is replaced or it is repaired by replacing
the EEPROM chip (U230 or U231), each output in the supply
must be recalibrated as described in Appendix A of the
Operating Manual. Since the EEPROM provides non-volatile
storage of the supply's Model number and GPIB address,
you must reassign these values before the calibration
procedures can be performed on the new (or repaired) GP
IB board. The GPIB address is set manually using the front
panel ADDR. key as described in Section III of the Operating
Manual. The supply's Model number is set as described in
the next paragraph.
4-21 Setting the Model Number
At turn-on, the supply's model number and letter suffix (e.g.
Agilent 6626A) are read out of the EEPROM along with
other constants which are required to program the supply
correctly. The model number constant specifies how many
and what type of outputs your supply contains and thus
establishes the programming limits for a particular supply.
in
The MODEL command is used to set the model number and
letter suffix of the supply. This was done before your supply
left the factory. However, when you replace a defective GP
IB board or repair an GPIB board by changing its EEPROM
chip, this setting may be lost and you must set the model
number using the MODEL command.
To assign a model number to your supply, the following
short program can be used with BASIC installed in an GPIB
controller. Note that in this programming example, it is
assumed that the GPIB Interface address is 7 and the
supply's GPIB address is 05 and your supply is an Agilent
Model 6626A.
4-11
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Table of Contents
Troubleshooting
