HP 35601A Operating And Service Manual page 74

6-20. Programmable Gain Steps Test
This test checks the circuits in the signal path shown in Figure 6-12. If the previous tests have
been performed, the only circuits checked are the relay K10, the switch S3, the 12dB
Amplifier, the 0-28dB Amplifier, the 6dB Attenuator, the 0-20dB Amplifier, the Integrator,
and the 6dB Pad. A signal is input into the 0-40MHz Input using an -hp- 3325A opt 001 set
at 5kHz. An -hp- 3455A Voltmeter measures the Channel A Output, then measures the 1MQ
OUTPUT to 3585A. The program checks that the Overload Flip-Flop is not set and the Out-
of-Lock Flip-Flop is set. If either of these conditions fails to occur, the user is given the op­
tion of trying the test again (after some troubleshooting) or discontinuing the test. The pro­
gram then selects all of the gains sequentially; for each gain change, the program adjusts the
level of the -hp- 3325A opt 001 a corresponding amount. So, if the attenuators and
amplifiers are working properly, a constant level should be maintained at the output. The
program confirms the output level for each gain step. In the next part of the program, the
user is asked to zero the DC offset of the 12dB Amplifier and gain stages. Finally, the pro­
gram prints the results of all the tests.
Initializing the Test
With the High Frequency Menu displayed, press shift SFK K2 (-hp-9836) or SFK K12 (-hp-
9845B) to initialize the test. After initialization, follow the instructions displayed on the
computer.
What if the Test Fails?
If the state of either flip-flop was incorrect at the beginning of the test, check the operation
of the detection circuits as well as the flip-flop circuits themselves. However, if the flip-flops
were in the proper states, and assuming that the previous tests have passed, the probable
causes of failure include the following:
• 12dB Amplifier
• 0-28dB Amplifier
• 6dB Attenuator
• 6-20dB Amplifier
• Integrator
• 6dB Pad
Using "SWITCH", vary the gain of the blocks (one at a time) and confirm that the gain
changes. Also make sure that the 12dB Amplifier, the 6dB Attenuator, and the Integrator
work by measuring the input and output of each. "SWITCH" should also be used to check
the operation of relay K10 and switch S3. Refer to Service Groups 2 and 3 for schematics,
component locators, and circuit descriptions.