Use a pair of diagonal cutters to remove the ferrule from
the new pin; then insert the pin into the old ferrule and sol
der the pin to both sides of the ferrule.
Maintenance—492/492P Service Vol. 1 (SN B030000 & up)
If it is necessary to bend the new pin, grasp the base of
the pin with needle nose pliers and bend against the pres
sure of the pliers to avoid breaking the board around the
ferrule.
Selected Components
Some components, such as microcircuits, are selected to
meet Tektronix specifications. These components carry only
Tektronix part numbers under the Mfr Part number column,
in the Replaceable Parts list.
Some circuits require a selected component value to
compensate for parameter differences between active com
ponents. These are identified on the circuit diagram and the
Replaceable Parts list. The Replaceble Parts list description
for the component gives either a nominal value or range of
value. If the procedure for selection is not obvious or com
plex, such as setting the gain or response of a stage, the
criteria for selection is explained in the Calibration or this
section of the manual. Where the selection procedure is ob
vious, such as establishing the frequency of an oscillator, no
procedure is given.
Installing Matched Crystals for the VR 100 Hz
Filters
The crystals for the 100 Hz filter circuit of the VR assem
bly are matched. The four crystals come with rubber tie
down straps. Plug the matched crystals into the two boards,
insert the rubber tie-down into the two holes provided on
either side of the crystal on the board and pull through until
the crystal is held in place by the tension of the rubber tie
down.
Replacing EPROM’s or ROM’s
Firmware for the microcomputer is contained in ROM’s
on the Memory and GPIB boards. Refer to the Replaceable
Electrical Parts list (Vol. 2) under these assemblies (A54
Memory, and A56 GPIB) for the versions and IC part
numbers.
Firmware Version and Error Message Readout
This feature of the 492/492P provides readout of the
firmware version when the power on/off is cycled. During
the initial power-up cycle, the firmware version flashes on
screen for approximately two seconds. The Replaceable
Electrical Parts list section, under Memory board (A54), lists
the ROM’s and their Tektronix part number for each
firmware version.
An additional feature is error message readout. The fol
lowing is a list of these messages and their meaning.
Error #
Meaning
57
Tune routine failed to carry from lower DAC.
58
Failed to phaselock.
59
Lost lock.
60
Failed to recenter when phaselock cancelled
or when going to an unlocked span.
Servicing the VR Module
The VR module requires mechanical support when it is
installed on board extenders. Mechanical support is pro
vided by moving the mounting plate at the upper side of the
module (Fig. 4-5A) to the bottom side. This allows installa
tion of a mounting screw through a support bracket into the
mounting plate screw hole as shown in Fig. 4-5B.
