Soldering Techniques; Disassembly Procedures - HP 8481H Operating And Service Manual

Service
HP 8481H/82H
Caution
The RF connector bead inside the Type N connector deteriorates
when contacted by hydrocarbon compounds such as acetone,
trichlorethylene, carbon tetrachloride, benzene, ...
Soldering Techniques
The Power Sensor is a high-sensitivity device, and is affected by very
small differences in temperature between its components. Therefore,
after the performance of any soldering in the unit, severol hours must
be allowed for the unit to reach thermal equilibrium before it is used
or tested
Capacitors A2C2, A2C3, A2C7, and A2C8 (figure 2) require
low-temperature soldering techniques. The connections to these
capacitors are a gold film deposited on a ceramic base. Molten solder
results in the gold forming an amalgam with the solder, and the
consequent removal of the gold from its ceramic base. Soldering must
be done quickly, and a low-temperature soldering iron and solder
must be used. The capacitors must be discarded if unsoldered. If
integrated circuit A2U1 or transistor A2Q1 is replaced, two of these
capacitors must be removed, and therefore must be replaced with
new ones,
a. Use a temperature controlled 600°F (311°C) soldering iron with a
zero crossover tip.
b. Low-temperature solder RMA flux, SN62.
Disassembly Procedures
CAUTIONS
«
Disassembly must be performed in the sequence described below,
otherwise damage may be caused to the two gold wires between the
A1 bulkhead assembly and the A2 input amplifier assembly. If these
wires are damaged, the A1 bulkhead assembly must be returned to
the factory for repair.
Each Power Sensor has an individually prepared graph on the
housing. If more than one Power Sensor is disassembled, be sure to
use the proper housing for each when they are reassembled.
Disassemble the Power Sensor by performing the following steps:
Caution
«
The gold wires connecting the A1 Bulkhead Assembly and the A2
Input Amplifier Assembly are extremely delicate and may be easily
broken. Be careful when working around them.
1. Insert the blade of a large screwdriver between the two-piece
plastic shell at the rear of the Power Sensor. Gently pry the
sections apart. (See figure 5.)
2. Proceed to the other side of the connector and again pry the cover
sections apart. Remove the shells and magnetic shields.
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