S E R V I C E N O T E S
1)
REPLACEMENT OF POWER TRANSISTORS:
If it is necessary to replace power transistors, the
following diagram (Fig. No. 4) must be followed to
mount new transistors. Also, there is a colored num-
ber indicating the transistor gain group on the case
of the transistor. The replacement transistor(s) must
have the same number and color as the one removed.
After a new transistor has been mounted with the
mica insulating washer, check to see if its case is in-
sulated from the heat sink. To do this, check between
the transistor case and the heat sink, with an ohmmeter.
If there is a resistance indicated, the case of the tran-
sistor is shorted to the heat sink.
A N Y C H A S S I S T O
COMMON CONNECTION MUST BE DISCONNECTED
WHEN MAKING THIS MEASUREMENT.
OUTPUT ADJUSTMENTS
The output stages of the
coupled from capacitors Cl4
SAX100 amplifier are direct
and Cl5 through transistors
Q10, Q11, Q12, Q13, Q14, Q15, Q16 and Q17 to the out-
put transformer primary. Replacement of transistors in
this circuit will require a check of the output balance to
insure best performance.
Required Equipment:
1) 50 mi II ivolt D.C. meter.
2) A.C. voltmeter capable
less.
of indicating .003 volt or
Potentiometer RP-2 and RP-3 control the zero signal
bias for Q10, Q13, Q16 & Q17 and Q11, Q12, Q14, &
Q15 respectively.
1)
2)
3)
4)
5)
Connect the O-50 mi llivolt meter across one of th
a
0.25 ohm 5 watt output emitter resistors. (R64,
R66 or R63, R65).
Adjust RP-2 or RP-3, whichever is associated
with the side of the amplifier being adjusted, set-
the voltage to 10 millivolts.
=
= 40ma).
Adjust the opposite side bias pot for minimum hum
and noise at the output as shown by the A.C. volt-
meter.
Check emitter resistor voltages. All should be
within the range of 5 - 20 millivolts. Adjust up
or down as required until all emitter voltages are
within limits. There is no interaction between the
adjusting potentiometers RP-2 and RP-3.
Potentiometer RP-1 is factory set for lowest dis-
tortion at rated power output at 1KC, and normally
should not require adjustment.
CAUTION: To obtain accuracy and to prevent meter
damage be absolutely certain that there is no signal
while making output adjustments. Turn volume control
down and do not introduce transients or hum by ac-
cidentally touching low-level components.
W
RAULAND-BORG CORPORATION
3535
West Addison Street
Chicago, Illinois 60618
_
KI-0961-A
8/71
Summary of Contents for SAX100
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