McIntosh MHT200, Service Manual

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T1
1
TUNER ALIGNMENT PROCEDURE
AM ALIGNMENT PROCEDURE
1.
Connect an AM Signal Generator to the RAA1 ”EXT
ANT” pin of the 5 pin connector. (Refer to Page 110.)
Connect a Distortion Analyzer to the MHT200 rear panel
TUNER INPUT RCA jacks. (These jacks act as the
Tuner Output.)
2.
Tune to bottom of band, and adjust T11 (AM OSC Coil)
for 3.0VDC at R46.
3.
Tune to top of band and adjust C64 (AM OSC Trimmer
Capacitor) for 26.0VDC at Connector R46.
4.
Repeat steps 4 and 5 as necessary for a Tuning Voltage
Range of 3.0 to 26.0VDC.
5.
Tune the Generator and Tuner to 600kHz, then adjust
Coils: T101 (AM ANT) and T12 (AM RF) for best sensitiv-
ity. Note: Coil T101 (AM ANT) is located on the RAA1.
It is labeled “L1”.
Note: Refer to Figure 1 while reading the below procedure.
FM ALIGNMENT PROCEDURE
1.
Connect an FM Signal Generator to Antenna Input.
2.
Connect Distortion Analyzer to the TUNER INPUT RCA
jacks. (These jacks act as the Tuner Output.)
3.
Remove Top Cover and AM/FM TUNER Cover. Turn On
the AC rocker switch. Press the red Standby button to
turn the unit On.
4.
Select Tuner with the Zone A selector knob. Put Tuner
into FM mode and tune to 87.5MHz.
5.
Adjust L5 (FM OSC Coil) for 3.5VDC at R46.
6.
Tune to 108.5MHz and adjust C59 (FM OSC Trimmer
Capacitor) for 24.5VDC at R46.
7.
Repeat steps 4, 5 and 6 as necessary for a tuning range
of 3.5VDC to 24.5VDC at R46.
8.
Tune the Generator and Tuner to 90MHz and adjust
Coils: L2 (FM MIX), L3 (FM RF) and L4 (FM ANT) for
best sensitivity.
9.
Tune the Generator and Tuner to 104MHz and adjust
Trimmer Capacitors: C60 (FM MIX), C62 (FM RF) and
C63 (FM ANT) for best sensitivity.
10.
Repeat 8 and 9 until no improvement in sensitivity is
noted.
11.
Tune Tuner to 90MHz with no RF Input and adjust T9
(FM DETector Primary) for zero volts between TP1 and
TP2 relative (connector J6).
12.
Tune the Generator to 90MHz and adjust the RF Output
to 1000uV and 100% MONO modulation at 1000Hz.
Then adjust T8 (FM DETector SECondary) for lowest
distortion.
13.
Reduce the Generator Output to minimum and detune
the Generator so the Receiver picks up only noise, then
recheck the voltage between TP1 and TP2 (connector
J6). Adjust T8 and C65 if needed. If it is not 0+/-
0.2VDC, repeat steps 11 and 12.If there is interference
from a station on this frequency, tune the Tuner to a
nearby frequency free from interference for this measure-
ment.
14.
Tune the Generator to 90MHz with a 1000uV output.
Then switch the Generator to stereo (left only) and adjust
T10 (FM IF Transformer) for the lowest distortion at the
TUNER INPUT RCA jacks.
15.
Switch the Analyzer to the right channel TUNER INPUT
jack and adjust R71 (MPX SEParation Pot) for best
separation (minimum output).
16.
Switch the Generator to the Right Channel and the
Analyzer to the Left Channel. Adjust R71 (MPX
SEParation Pot) and check for best separation (mini-
mum output).
17.
Disconnect voltmeter from TP1 and TP2 (J6). Reduce the
generator output to 5uV and adjust R73 (STEREO
SWITCH Pot) so the MPX light (Dot next to Signal
Strength number) just comes on.
6.
Tune the Generator and Tuner to 1400kHz, then adjust
Trimmer Capacitors: C106 (AM ANT) and C61 (AM RF)
for best sensitivity. Note: Trimmer Capacitor C106 (AM
AMT) is located on the RAA1. It is labeled “C1”.
7.
Repeat 8 and 9 until no improvement in sensitivity is
noted.
8.
Note the initial position of R70, and then adjust R70 fully
counter clockwise. Tune the Generator and Tuner to
1400kHz (20uV, 30% modulation), then Adjust T7 (AM
IF) for maximum signal.
9.
Tune the Generator and Tuner to 1400kHz (100mV, 30%
modulation). Slowly adjust R70 clockwise until the
MHT100 front panel signal strength display reads “9”.
10.
Check both channels for signal to noise performance,
and re-adjust R70 and as needed.
105 106
Figure 1