Removal and Replacement of Transistors Q2 and Q3

11-6625-467-34

tension, remove the collector stud hexagonal nut

(3) Remove the lockwasher and fiber washer

(16) on transistor Q3 (4).

from the diode stud.

(4) Remove the solder lug (20) and wires (do

(4) Lift the diode up and remove it from the

not remove wires from solder lug) from the collector

chassis.

stud.

NOTE

(5) Remove the four machine screws (19) that

T h e insulating sleeve may stay in the

hold the blower air filter (2, fig. 3-27) to the front

chassis; if so, let it remain there for use

panel.

with the replacement diode.

(6) Remove the blower filter (2).

(7) Remove transistor Q3 (4) from the heat sink

b. Replacement.

(5) in the blower wall.

(1) Place the mica washer over the hole in the

b. Replacement.

chassis.

(1) Place the transistor on the heat sink in the

(2) Slip the solder lug over the stud on the

blower well ( guide pin on transistor prevents incor-

replacement diode and push the stud through the

hole in the chassis.

rect mounting of the transistor).

( 2 ) Hold the transistor on the heat sink with

( 3 ) Slip the insulating sleeve over the stud

from the bottom of the chassis and slide it into the

one hand and slip the solder lug (20) (with wires)

over the collector stud with the other hand.

chassis hole so that the diode stud is insulated from

the chassis.

(3) While still holding the transistor on the

heat sink, start the hexagonal nut (16) on the collec-

(4) Place the fiber washer and lockwasher on

tor stud and tighten thumbtight.

the diode stud.

CAUTION

Do not overtighten the collector stud hex-

Do not overtighten the diode nut; the stud

agonal nut (16); the stud threads may strip.

threads are made of a copper alloy for good

electrical connection, and they will strip

(4) Lift up the inverter transformer bracket

quite easily.

( f i g . 3-5) approximately inch; use a socket

wrench and extension to tighten the hexagonal nut

(5) Place the nut on the diode stud and tighten.

on transistor Q3.

CAUTION

(5) Replace the four machine screws (19) in the

When soldering the anode lead, place a

front panel and the four machine screws (19) in the

heat sink (such as long-nosed pliers) be-

r e a r panel that secure the inverter transformer

tween the soldering iron and diode.

bracket.

(6) Replace the blower air filter (2) and four

(6) Solder the wire to the diode anode lead.

machine screws (19) on the front panel of the test

3-12. Removal and Replacement of

set.

Transistors Q2 and Q3

NOTE

(fig. 3-5 and 3-7)

S e e soldering hints in paragraph 3-9b

Transistors Q2 and Q3 are mounted on heat sinks

before soldering the wires to the emitter

l o c a t e d on each side of the blower BL1 well

and base connectors of the transistor.

assembly (fig. 3-5). The stud nut on transistor Q2 is

accessible and can be removed without difficulty;

(7) Solder the wires to the emitter and base of

h o w e v e r , special procedures are necessary for

the new transistor.

removing and replacing transistor Q3. Follow the

3-13. Removal and Replacement of Filter

procedures in a and b below when removing or

Capacitors C1, C2, C3, and C8

replacing transistor Q3.

(fig. 3-3 and 3-5)

a. Removal.

Capacitors C1, C2, C3, and C8 are large filter capaci-

(1) Unsolder and identify the wires from the

tors mounted in plastic retainers in the extreme up-

transistor base and emitter terminals. (Do not un-

per right hand corner of the test set chassis. When

solder wires on collector terminal lug. )

removing or replacing these capacitors, follow the

(2) Remove the four machine screws (19) from

procedures in a and b below.

the front panel and the four machine screws (19)

a. Removal.

f r o m the rear panel that secure the inverter

(1) Remove the two screws along the top of the

transformer bracket (fig. 3-27).

front panel and the top screw on the right side of the

(3) Lift up the inverter transformer bracket

f r o n t panel (located between the EXTERNAL

(approx. inch) and, using a socket wrench and ex-

3-40