McIntosh MR 71

ALIGNMENT
ADJUST
TEST
LIMITS
REMARKS
Top (Secondary)
and
bottom (Primary)
cores of T1, T2,
T3, and T4
Maximum
possible
negative
voltage
Shunt to ground the winding not being adjusted with a .01MF capacitor
in series with a IK resistor. Attenuate signal generator until output
voltage at TP #1 is less than 1.5 volts with one IF transformer winding
shunted. IF transformers have terminal #1 marked with a green dot
and are numbered clockwise.
T5 Primary
(Bottom core)
Same as
above
'
T5 Secondary
(Top core)
Adjust for
0 volts
T6 Primary
(Bottom core)
Maximum
negative
voltage
If a distortion analyzer is available, omit this step at this time. Adjust
T6 primary after step 9. At that time, use a strong signal from FM
generator, modulate 100%, and use 75KC deviation. Adjust primary
for minimum distortion. Should be no greater than 0.5%.
T6 Secondary
(Top core)
Adjust for
0 volts
Oscillator
Trimmer
Maximum
negative
voltage
As output increases, attenuate signal generator to keep maximum output
at TP # 1 to a low level. By doing so, precise alignment can be achieved.
Oscillator
Coil
SAME
Repeat steps 6 and 7 until dial calibration is accurate.
Mixer trimmer,
RF trimmer, and
Antenna trimmer
SAME
Mixer, RF, and
Antenna coil
Tuning slugs
SAME
Repeat steps 8 and 9 until output is as high as possible.
Muting adj.
control
Turn muting switch to “in” position. Adjust muting control until
background noise just disappears.
IHFM
sensitivity
2.5 microvolt
for 3% total
noise and
distortion
Step 11 is an overall sensitivity check, and requires a distortion analyzer
and FM signal generator with attenuator.
With 2.5 microvolts input at the 300 ohm antenna terminals, TP #1
voltage should be 3.0 volts or more.