Model 185B Section V
Paragraphs 5-36 to 5-41
I
Figure 5-3. Disassembly for Power Transistor Replacement
5-36. TUNNEL DIODE REPLACEMENT. Tunnel b. Reheat solder around holes and quickly insert
diodes are more sensitive to heat than other semi- a toothpick to clean holes in preparation for inserting
conductors. Particular care is required in their new component. DO NOT use an awlor similar sharp
replacement. metallic object to ream the hole. Doing so may re-
move plating from hole.
5-37. SERVICING ETCHED CIRCUIT BOARDS. c. Preform new component leads to fit holes ex-
actly. Insert new component carefully, without forc-
5-38. GENERAL. Component miniaturization in this ing it.
instrument has resulted in the use of a board with
conductor material on both sides. Good conductivity d. Resolder by applying heat to component lead on
between sides has been assured by plating the inside component side of board. Use just enough solder to
of component mounting holes. This method of con- assure a good connection. Clean off excess flux.
struction presents the need for new techniques in
etched circuit board repair. 5-40. When heavy, multi-lead components such as
tube or transformer sockets must be replaced, good
5-39. Proceed as follows: practice is to remove component by clipping the com-
ponent pins one by one and unsoldering the pins
a. Using a clean soldering iron, so that good heat individually.
transfer is obtained, apply heat (near circuit board)
to one lead of component to be removed. Repeat for
other leads.
5-41. CRT REPLACEMENT.
CAUTION
WARNING
AVOID EXCESSIVE HEAT. Use a 25- to Handle crt with care. Wear gloves and
40-watt soldering iron. Excessive heat will
cause copper circuit to lift from board. Use plastic face mask or goggles.
a heat sink (e.g., pair of long-nose pliers) a. Remove instrument cabinet.
between soldering iron and component. See
paragraph 5-36 for special techniques in b. Remove four mounting screws from bezel, and
replacing tunnel diodes. remove bezel and graticule.
01255-1 5- 5 |
ACEC
