Adjustments; Introduction; Data Probe Threshold Voltage Check And Adjustments; Power Transformer Primary Line Voltage Change Procedure - HP 5004A Operating And Service Manual

INTRODUCTION

5-2. This section describes adjustments that may be made to the 5004A. Only two adjustable
functions exist. The power transformer primary is switchable to allow selection several different
line voltages, and the data probe input threshold voltage is adjustable to allow the exactly cor-
rect value to be set. The 5004A top cover must be removed to change the power transformer
primary (line voltage change). The data probe covers must be removed to set the threshold.
Refer to disassembly procedures in Section Vlll for cover removal information.
The data probe threshold voltage should be checked when any parts
are replaced in the data probe or when the power supply +5-volt
regulator is replaced.
DATA PROBE THRESHOLD VOLTAGE CHECK A N D ADJUSTMENT
Use the following procedure to check and adjust the data probe threshold voltage. Refer
5-4.
to the recommended test equipment listed in Section for units necessary in this procedure.
a. Refer to the disassembly procedures in Section
Refer to the parts location figure and schematic diagram in Section Vlll for other infor-
mation necessary for this procedure.
b. Connect the negative test lead of the DVM to the Data Probe U2(1), and connect the
positive test lead to Ul(7). Record this voltage (Vcc).
c.
Connect the positive test lead to Ul(5). Compare this voltage with the Vref voltage cor-
responding to the Vcc (step b) on Figure 5-7.
d. If necessary, adjust potentiometer R4 so the Vref voltage corresponds to Vcc voltage
b.
taken in step
Figure 5-7 i s a graph relating the U1 pin 5 voltage to U1
pin 7 voltage.
e. Repeat steps b, c, and d.
f. Disconnect the test equipment, and reassemble the data probe covers.
POWER TRANSFORMER PRIMARY LlNE VOLTAGE CHANGE
PROCEDURE
5-6. Use the following procedure to change the power transformer primary line voltage
switches settings.
a. Refer to the disassembly procedure in Section VIII, and remove the 5004A top cover.
DISCONNECT THE LlNE POWER CABLE F R O M THE 5004A.
SECTION V

ADJUSTMENTS

NOTE
and remove the data probe covers.
NOTE
WARNING
Model 5004A
Adjustments