Servicing Etched Circuit Boards; Servicing Rotary Switches; Servicing Tuner Assembly - HP 652A Operating And Service Manual

5-58. SERV ICING ETCHED CIRCUIT BOARDS.
5·59. The Model 652A contains three plated·through.
double-sided, etched circuit boards. When working on these
boards, observe the following rules to prevent damage to
the circuit board or components:
a. Use a low·heat (25 to 50 watts) soldering iron with a
small tip.
b. To remove a component, clip a heat sink (long nose
pliers, commercial heat sink tweezers, etc.) on the compo­
nent leas as close to the component as p ossible. Place the
soldering iron directly on the component lead, and pull up
on the lead. If a componen t is obviously damaged or faulty.
clip the leads close to the component, and remove the leads
from the board.
Excessive or prolonged heat can lift the circuit
f oil from the board or cause damage to
components.
c. Clean the component lead holes by heating the solder
in the hole, quickly removing the soldering iron, and
inserting a pointed, non-metallic object such as a toothpick.
d. To mount a new component, shape the leads and
insert them in the holes. Clip a heat sink on the component,
heat with the soldering iron, and add solder as necessary to
obtain a good electrical connection.
5·60. SERV ICING ROTARY SWITCHES.
5·6 1 . The Model 652A contains two rotary type switches:
FREQUENCY RANGE and OUTPUT ATTENUATOR.
5-20
Spdion
V
When working on these switches, observe the following
rules :
a . Use a low heat (25 to 50 watts) soldering iron with a
small tip.
h .
When replacing components, attempt to dress them
as nearly to their original alignment as possible.
c. Clean excessive flux from the connection and ad­
joining area.
d. After cleaning the switch, apply a light coat of
lubriplate to the switch detent balls. DO NOT apply
lubricant to switch contacts or allow lubricant to contami­
nate components.
e. To eliminate excessive contact wear and oxidation,
the contacts may be lubricated with Electrolube 2G, ·hp·
Part No. 5060-6086. Only a very small amount of lubricant
is necessary. Note : Electrolube 2G will change to a reddish
brown color with time ; however, the lubricating properties
are not affected. A more detailed description on how to
apply Electrolube 2G is available at no cost from your local
Sales and Service Office. Ask for Service Note M45.
5·62. SERVICING TUNER ASSEMBLY.
5-63. When replacing the tuning capacitor, C l . make
certain that the tuner coupler and the frequency dial shaft
are aligned to prevent binding of the FREQUENCY dial or
VERNIER control. If necessary, remove the frequency dial
knob, frequency dial, and loosen the tuner drive assembly
(casting and spur gears) retaining screws ; then align tuner
coupler and frequency dial shaft. Tighten retaining screws
after tuner coupler and dial shaft are aligned.
NOTE
For correct alignment, refer to Frequency Dial
Calibration. Paragraph 5-29.
Mode1 652A