Fisher 700-T - IF Amplifier Alignment Procedures; IF Alignment Procedure; FM Tuning Meter and Muting Adjustment

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IF ALIGNMENT
@ Connect 10.7-MHz (Mc) sweep generator to TP751 on front
end. Disconnect jumper between terminals 3F and 3G on IF
boord. Connect scope vertical input through 220K resistor to
TP301, :
NOTE: Connect ground lead of generator to ground near TP751
and ground of scope closest to scope input.
@ Adjust generator output voltage and frequency to observe IF
response curve. Use as low a generator output as possible.
Measure voltage at TP301 with OC VTVM during alignment
ond readjust generator output to keep meter treading from —] 4
to +~+2.0 VDC maximum.
@ Detune top core of 2303 outwards.
@ Align bottom core of 2303, top and bottom cores of 2302,
2301 and Z751 for maximum gain and symmetry ~see Figure 1. ;
Repeat alignment.
@ Reconnect jumper between terminals 3F and 3G. Disconnect
wire from TP302 (terminal 3N) and connect scope vertical in-
put through 220K resistor to TP302.
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1381-1 10.7 MHz IF AMPLIFIER
BOARD VIEWED FROM COMPONENT SIDE
®@ Align top core of 2303 for maximum gain and symmetry—see
Figure 2.
@ Disconnect scope ond reconnect wire to TP302. Connect
DC VTYVM to TP302.
© Set generator output to 10.7 MHz (Mc) with no sweep. Vary
generator voltage from minimum to maximum; reading on DC
VTVM should increase with Increase in signal.
@ Connect DC VT VM across resistor R4. Vary generator voltage
from minimum fo maximum; reading on OC VTVM should de-
crease with increase in signal,
@ Set generator voltage to 200mV. Adjust Meter Adjust Pot.
R14 for tuning meter reading of 4.
@ Connect scope vertical input through enth resistor to ter-
_ minal 3K.
© Set generator for sweep and adjust penureies output voltage
to observe ratio detector response, Use as low o generator
output as possible.
@ Adjust top and bottom cores of Z304 for maximum gain; re-
adjust top core for best linearity~sea Figure 3.
+19V test
AFTER IF
ALIGNMENT
MUTING
TEST POINT 30! = =
JUMPED
| FA TUNING HETER CALIBRATION |
@ Connect on FM generator to the NORM antenna terminals.
Use a 120-ohm composition resistor in series with each lead
from the generator.
@ Set FM generator frequency and TUNING dial pointer to 90
MHz (Mc). Set generator output to 20 mV, $22.5 kHz (ke)
devistion with 400 Hz {cps}.
@ Adjust top core of 2303 for maximum reading on tuning
meter.
@ Increase generator output to 200 mV. Adjust Meter Adjust
Pot. Rid for meter reading of 4.5.
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OUTPUT
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© “| AUDIO
ALL BOARDS
4 4 FOR VALUE
SEE SCHEMATIC
FM MUTING ADJUSTMENT
Set MUTING switch to OFF.
@ Connect an FM generator to the NORM antenna terminals.
Use a 120-ohn composition resistor in series with each lead
from the generetor,
@ Connect AC VT VM to LEFT or RIGHT CHANNEL RCDR
HIGH jack.
@ Set FM generctor frequency ond TUNING dial pointer to 90
MHz({Mc). Set generator output to 20 uV, 22.5 kHz (ke) de-
viotion with 400 Hz (cps).
®@ Adjust TUNING knob for maximum reading on tuning meter.
Note reading on AC VTVM.
@ Set MUTING switch to ON. Adjust Muting Adjust Put. R16
for reading on AC VTVM 1 to 5 db lower than thet previous ly
noted,
@ Reduce generator voltage to zero—no signa! (400 Hz modu-
lation) or noise should be indicated on AC VTVM ot RCDR
HIGH jock.