Agilent Technologies 2712A A2 Digital Assembly to A3 or A10 Output Assembly Interface, Equipment

Service Model 8904A

A2 DIGITAL ASSEMBLY TO A3 (OR A10) OUTPUT ASSEMBLY INTERFACE

Description

The following procedure will help identify whether an instrument failure is due to the analog output circuits or their control inputs. Since the layout of the instrument board assemblies breaks the circuit assemblies along digital-analog lines, this procedure will also help determine which assembly (the A2 Digital Assembly or the A3 (or A10) Output Assembly) is at fault. It does this by checking signals on the interface between the two assemblies.

If the tests pass but the output is faulty, the A3 (or A10) assembly should be replaced. If the tests fail, trace the signal to the A2 assembly. Retest the line that was faulty to determine whether the fault is in A2 or its interconnection to A3. Refer to Table 8-2,A3 and A10 Interconnections to A2, at the end of this procedure for a cross reference of the signal interconnections.

Equipment

Counter	HP 5315B
Digital Multimeter	HP 3478A
Oscilloscope	HP 1740A or Tektronix 2235

Procedure

1.Preliminary Setup

a.If the instrument has Option 002 (a second output assembly, A10) and Output 1 (the output from the A3 Output Assembly) is to be checked, move the A10 Output Assembly out of the way. (Refer to Figure 8-11, How to Access A3 in Instruments Equipped with Option 002.)

b.Check that switches 1and 2 of the Service Switch, S1, on the A2 Digital Assembly are open and switches 3 through 10 are closed.

NOTE

The reference designators called out in the procedures are for the A3 or

A10 Output Assembly.

2.Power Supply Checks

Connect a voltmeter to the points shown in Figure 8-12,Power Supply Testpoints on A3 or AlO. The readings should be very close to those indicated.

3a. Clock Checks (Using an Oscilloscope)

NOTE

This procedure is adequate for most cases. Step 3b (which uses a counter), however, is more exact.

a. Connect a dc coupled, high-impedance oscilloscope to pin 3 of U2. The waveform should be a TTL squarewave with a period of approximately 150 ns (a frequency of 6.7 MHz).

b.Connect the oscilloscope to pin 2 of U2. The waveform should be a TTL squarewavewith a period of approximately 600 ns (a frequency of 1.68 MHz).

8-30 Troubleshooting (Digital/Output Interface)