HP 33120A User manual

HP 33120A / Option 001
Phase-Lock Assembly
Installation Instructions for Retrofit Kit
Part Number 33120-90021
October 1998
©Copyright Hewlett-Packard Company 1994, 1998
All Rights Reserved.

This guide contains information to install the Phase-Lock assembly into
the HP 33120A. This assembly can be installed only in instruments
shipped after August 1994 with serial numbers US34004078 and above.
Refer to the HP 33120A /Option 001 User’s and Service Guide (included
with the retrofit kit) for complete details on using the assembly.
Installing the Phase-Lock Assembly
1 Remove the outer cover from the HP 33120A.
HP 33120A /Option 001
Phase-Lock Assembly
Installation Instructions for 33120-80001 Retrofit Kit
Loosen
Captive
Screws
Remove
Bottom Screw
Slide Off Outer Cover
b
a

2 Carefully cut two holes in the rear-panel label.
The Ref Out and Ext Ref In terminals on the Phase-Lock assembly will
extend through these holes in the HP 33120A rear-panel.
3 Connect the coaxial cable to the Phase-Lock circuit board.
Connect one end of the coaxial cable (included with the retrofit kit) to
the connector labeled P2 on the Phase-Lock circuit board. Position the
cable as shown.
2
Cut Out Holes
Coaxial Cable (33120-61603)
P2
P2

4 Install the Phase-Lock assembly in the HP 33120A chassis.
Before installing the Phase-Lock assembly, make sure that the red and
black wires for the instrument fan are clear of the rear-panel holes.
With the Phase-Lock assembly positioned trace side up, insert the two
BNC connectors through the holes previously cut in the rear-panel label.
5 Secure the Phase-Lock assembly in place.
As shown above, place one lock washer and one hex nut (included with
the retrofit kit) on each of the two BNC connectors. To prevent cross-
threading, be sure to hand-tighten the hex nuts at least one turn before
using a tool.
3
Lock Washer (2190-0699)
Hex Nut (2940-0256)
Trace Side Up
Top View
Side View

6 Connect the coaxial cable to HP 33120A circuit board.
First, slide the black ferrite bead to the end of the coaxial cable as shown.
Then, connect the coaxial cable to connector J401 on the HP 33120A
circuit board. Be sure to position the cable away from the heatsinks on
the circuit board.
7 Connect the ribbon cable to the HP 33120A circuit board.
Connect the loose end of the grey ribbon cable to connector J102 on the
HP 33120A circuit board. Press down firmly on the ribbon cable
connector and secure the cable in place with the locking clips.
4
Ferrite Bead
J401
Ribbon
Cable J102
Snap the Locking Clips
over the top of the connector
to secure the Ribbon Cable.

Calibration /Adjustment Procedure
After installing the Phase-Lock assembly, perform the frequency
adjustment procedure (CAL:SETup 0) on page 67 in the HP 33120A
Service Guide. Be sure to make the 1 kHz frequency measurement with
an accuracy of at least 8 digits (0.01 ppm). You may be required to
perform up to three iterations of the frequency adjustment following
initial installation of the Phase-Lock assembly.
For complete details on performing a calibration, see chapter 4 in
the HP 33120A Service Guide.
5