Service manual

FIGURE J.
SR110 TOP VIEW, COVER REMOVED
Fuse Replacement
The SRl10-2E (only) contains a 1/16A, Slo-Blo,
wired-in (pigtail) fuse which protects the power trans-
former. Be sure to replace this fuse only with one of
identical value and size.
Printed Circuit Board Removal
The SR110 chassis contains a printed circuit board
assembly (see Figure
J). The foil side of the board
may be made accessible for servicing by disconnecting
leads
K and L, and removing the eight knobs and
nuts securing individual channel Volume Controls
R1
through R8 to the front panel. The board may be com-
pletely removed by unsoldering the 17 wires fastened
to the board.
IMPORTANT: When disconnecting sol-
dered board connections, make sure each wire is
identified for proper reconnection. This may be done
by affixing a piece of masking tape marked with the
connection or terminal letter to each wire.
Replace cover after servicing.
CIRCUIT BOARD WIRE COLORS
Letter
I Wire Color I I Letter I Wire Color
A
B
C
D
E
F
G
H
NOTE:
6
Brown
White/Red
Orange
Yellow
Green
Blue
Purple
G rav
Orange (2)
Bare
Bare (Shield)
Red
Black
Red
Red
Blue
Production variations may result in wire colors dif-
fering from those in the
table.
Transistor and Diode Removal
All transistors and diodes used in the SRllO are
mechanically supported by their leads. When replacing
these devices, proper lead configurations must be fol-
lowed. Minimum soldering heat (preferably with a low-
wattage soldering iron) should be used to avoid
damage to the device. Transistor lead codes are in-
cluded in the Notes to Circuit Diagram (Figure
L).
Transistor and Diode Checking
Defective transistors and diodes may be located by
use of a standard ohmmeter such as a
Simpson 260.
Polarity of the ohmmeter must be verified before these
checks are made. Transistors and diodes must be
removed from the circuit before testing.
With a known diode orientation, measure the diode
resistance in the forward and reverse directions. The
lowest meter reading will establish the probe at the
cathode end (schematic symbol arrow points to cath-
ode) as the "minus" probe while the other probe will
be "plus." Some ohmmeters are not polarized in this
manner with relation to "volts plus probe" and "volts
minus probe." With the ohmmeter "plus" probe on the
anode end of
a diode, and the "minus" probe on the
cathode end, the ohmmeter should read approximately
2000 ohms or less. With the meter probes reversed, a
reading of about 10,000 ohms or more should be ob-
tained. If either of these conditions is not met, the
diode should be replaced.
To check transistors, the ohmmeter should be set to
the 100- or 1,000-ohm scale. If all conditions in the
following table are met, the transistor may be
con-