Input Resistance Test Set-Up - HP 75000 C Series Service Manual

4-1 1. Input Resistance
This test checks the input resistance of the vertical inputs. A four-
jest Procedure
wire measurement is used for accuracy
at
50 R.
1. Connect the equipment as shown below.
Use the BNC-to-banana
adapters
to
connect one of each BNC cable
to
the four-wire resistance
connections on the multimeter, and connect the free ends of the
cables
to
a BNC
tee.
Connect the male end of the BNC tee to the HP
E1426A channel 1 input.
BNC TO DUAL
MULTIMETER
LO BNC CABLE COMMAND OSCILLOSCOPE
MODULE MODULE
Notes
Flgure 4-2. Input Resistance Test Set-up
2. Set the HP E1426A controls as follows:
Reset HP E1426A
...............................................
*RST
Channel
1
DC a t 1Mn
..........................
CHAN1:COUP DC
3. Verify the Multimeter reads 1MR flOkR.
4.
Set the HP E1426A channel
1
controls to 50R (CHAN1:COUP DCF).
5. Verify the Multimeter reads 5W
*0.5R.
6. Repeat steps 1 through
5 for channels 2,3, and
4.
When repeating the procedure, all references to channel 1 should be
changed
to
the channel being tested.
Failure of this test indicates a faulty attenuator if resistance is out of
specifications. One of the PCA's also may be a t fault if input resistance
cannot be changed. See troubleshooting in Chapter 8.
7. Disconnect test equipment.
4-6
Verification Tests