PREAMP/AMP
TESTS AND ADJUSTMENTS
All adjustments should be made after a minimum of a
10 minute warm-up.
1 Remove the 12AX7 (V-9).
2 Measure the voltage at TP#3. Voltage should
be 0.7 volts positive. If it is not 0.7 volts, ad-
just R-8.
3 Do likewise with TP#4 and R-9, TP#5 and
R-10, TP#6 and R-11.
4 Re-insert the 12AX7.
5 Feed a 1 KC signal into AUX. Drive the amp to
full 30 watts output. Be sure all controls are
set for a flat response. Check to be sure the
channels have equal output with equal drive
from the audio oscillator. If channels are un-
balanced, adjust R-55, This control is found on
the left preamp printed circuit board. It will
vary the output of the left channel. The preamp
cover must be removed to gain access to this
control.
6 Measure harmonic distortion at 30 cycles. Ad-
just R-6 for minimum distortion on the left
channel and R-7 for the right. Distortion must
be less than 0.5%. The bottom cover must be
removed to adjust these controls. They have
blue plastic knobs.
7 Now measure distortion at 2KC and 20KC.
Must be less than 0.5% at full output.
8 Next, feed a signal thru the phono inputs.
Check for correct RIAA equalization.
9 Remove all inputs. Check hum and noise on
phono 1. Should be at least 60db below rated
output.
DIAL STRINGING
8
