Emerson Keystone Figure 637, Service Manual

Page: 15 / 37

p
Emerson Radio
Figure 5-7— Location o f Alignment Points
AUDIO I-F ALIGNMENT: (Table V ) .
STEP
SIG N A L GENERATO R IN P U T M E A SU R IN G
IN S T R U M E N T
A D J U S T
PROCEDURE
RESPONSE
CURVES
C O N N E C T IO N
FREO U EN CY
1
Marker generator
through .001
mfd. to pin 2 of
V 4. Low side
to B— .
Marker-—4.5
MC.
Connect v.t.v.m.
Connect v.t.v.m.
to junction of
R38 and C27.
Low side to B— .
C79 Peak for maximum re­
sponse. Adjust generator
input to produce one volt
reading on v.t.v.m.
2 99
Marker— 4.5
MC.
99
T5
(Top and
bottom)
Peak for maximum
response
3
Connect sweep
generator in
parallel with
marker gen.
Sweep— 4.5
MC. (450 KC.
sweep) Marker
— 4.5 MC.
Replace v.t.v.m.
with scope con­
nected through
10K resistor to
junction of R44
and C31.
T 6
(Bottom)
Position 4.5 MC- marker
at center of S-curve, by
adjusting secondary
bottom.
'• * •
♦150 KC.
4.5 MC. /
4
99 99
99
T 6
(Top)
Peak primary for maxi­
mum amplitude and
linearity. Repeat step 3.
^ - / ^ - I 5 0 K C .
b. V ID E O I-F A L IG N M E N T :
1) Retain the control settings used for audio i-f
alignment.
2) Connect a 3 volt bias battery from the junction
o f R l, R6, and R l l (negative terminal), to
chassis (positive terminal) for step 5.
3) Shape the overall response curve, after indi­
vidual peaking of stagger-tuned and over­
coupled i-f transformers.
Maintain output of
the sweep and marker generators at a mini­
mum, to prevent distortion of the response
curve.
15
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