Shure SR105 service manual Small Signal and Predriver Transistors, Driver Transistors

	Main Circuit Board
Letter	Wire Color	Letter	Wire Color
A	Blue	J	Yellow/Black
B	Black	K	Orange/Black
C	Gray	L	Orange
D	Green/Black	M	Brown
E	Violet	N	Yellow
F	Red	P	Green
G	White	R	White
H	White
	Filter Circuit Board
; "Yellow		1;	; "
			2Yellow/Black
	-	-	-

NOTE: Production variations may result in wire colors dif- fering from those in the table.

SMALL SIGNAL AND PREDRIVER TRANSISTORS

Transistors Q1 through Q6, Q13, Q14, and Q201 through Q203 are mounted on printed circuit boards. When re- placing these transistors it is imperative that proper lead configuration be followed. A minimum of soldering heat should be used to avoid damage to the transistor or printed circuit board. Refer to the Notes to Circuit Diagram (Figure 20, Page 23) for the transistor lead codes.

DRIVER TRANSISTORS

Driver transistors Q7 and Q8 (Figure 13, Page 13) are mounted on a bracket located on the top surface of the Amplifier chassis. Before removing these transistors, write down the lead color and location at each transistor solder junction. When replacing transistors, apply Wakefield Type 120 thermal joint compound to each side of the insulating wafer to provide good heat transfer from transistor to bracket. After replacement and before connecting transis- tor leads, check the transistors between case and chassis with an ohmmeter; there should be no continuity. Be sure that these transistors are not interchanged in the circuit; they are not identical devices. Q7 is an NPN transistor and Q8 is a PNP transistor. Refer to the Notes to Circuit Diagram (Figure 20, Page 23) for the transistor lead codes.

R 4 5 R46 R 3 0J 6

W I

F2

(XF2)

FI

TI

F3

R4

841

	Al	R27 PLI	R 3 7 C14	C15	R3
MPI	MP4				DII	MP5

*SR105A MODEL ONLY

FIGURE 14. SR105 POWER AMPLIFIER BOTTOM VIEW,

COVER REMOVED (SR105A MODEL SHOWN)