HP 35601A Operating And Service Manual page 116

Model 35601A
Service
6 82. TROUBLESHOOTING THE DIGITAL CIRCUITRY OF THE A1 BOARD
This troubleshooting procedure should be used when the Digital Signature Analysis Test
(test 18 from the Automatic Tests and Adjustments) completely fails, or when the -hp-
35601A is not responding to HP-IB command. These symptoms indicate that the handshake
is not occurring; use the following procedure when this occurs. If all of the tests pass, the Al
Board should be able to handshake with HP-IB.
a. Disconnect the HP-IB cable and do the following:
1. Check that 'DIOl' through 'DI08', 'ATN', 'IFC, and 'DAV are biased at about
2.4v (TTL logical high).
2. Ground 'DIOl' through 'DI08' at the inputs of U7 and U14; check for the correct
levels at the output of U20.
3. Ground 'ATN', 'IFC, and 'DAV; check for the correct logic levels as far as
possible.
4. Switch each HP-IB select code switch and check for the correct levels at inputs of
U23andU31.
b. Cycle the power and check that the start-up sequence works by doing the following:
1. Check start-up pulse with scope at U34 pin 4.
2. Check address flip-flop (FF3) U25 pin 8 for a low.
3. Ensure that Ql is high and Q2 is low.
4. Check that the ADDRESSED indicator on the front panel is off.
c. Ensure that the address flip-flop (FF3) will set and that the handshake works by doing the
following:
1. Set the HP-IB address switches to 00001.
2. Ground 'DIOl', 'DI06\ 'DAV, and 'ATN'.
3. Check that Ql is low and Q2 is high (changed states).
4. Check that 'NRFD' is low and 'NDAC is high.
5. Check that the ADDRESSED indicator on the front panel is on.
d. Check that the address flip-flop (FF3) will stay set and that the rest of the handshake
works by doing the following:
1. Remove the ground from 'DAV.
2. Check that Ql is low and Q2 is high.
3. Check that 'NRFD' is high and 'NDAC is low.
4. Check that the ADDRESSED indicator on the front panel is still on.
e. Check ATN operation by doing the following:
1. Remove the ground from 'ATN'.
2. Ground 'DAV, then remove the ground.
3. Check that the address flip-flop (FF3) LED is still on.
4. Check that the latch state LEDs L0-L3 are 1000.
5. Move the ground from 'DIOl' to 'DI02'.
6. Repeat step 2.
7. L0-L3 should be 0100.
8. Move the ground from 'DI02' to 'DI03'.
9. Repeat step 2.
10. L0-L3 should be 0010.
11. Move the ground from 'DI03' to 'DI04'.
12. Repeat step 2.
13. L0-L3 should read 0001.
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