Emerson Keystone Figure 637, Service Manual

Page: 12 / 37

Emerson Radio
Proper adjustment of the H O R IZ O N T A L and
V E R T IC A L L IN E A R IT Y controls, and the SIZE
controls should result in test patterns in which the
circles are round and the wedges are linear and equal.
The test pattern circles should be concentric with the
curved sides of the mask.
955282
C H A N N E L
V ID E O
CARRIER
M C
A U D IO
CARRIER
MC.
2
55.25 59.75
3
61.25
65.75
4
67.25 71.75
5
77.25
81.75
6
83.25 87.75
7
175.25
179.75
8
181.25 185.75
9
187.25 191.75
10
193.25
197.75
11
199.25
203.75
12
205.25 209.75
13
213.25
215.75
TO
GEN
120
- A / W
50
TO
R E C E IV E R
Figure 5-4— Rear Deflection Adjustments,
*For chassis not equipped with wobble plate and
centering lever .
6. ALIGNMENT TEST EQUIPMENT — Proper
servicing and alignment of Chassis 120110B and 120-
113B requires the equipment indicated.
a. SW EEP G E N E R A T O R :
1) Frequency ranges of 18 to 30 MC., 50 to 90
MC., and 170 to 225 MC.
. 2) Sweep width variable to 10 MC.
3) Output of at least 0.1 volt, with an attenuator
for adjustment of output.
4) Constant output over sweep width, with flat
output on all ranges and at all attenuator posi­
tions.
5) Output impedance of 300 ohms, for r-f align­
ment, or matching network. See figure 5-5.
b. M A R K E R G E N E R A T O R :
1) Frequency ranges of 4 to 30 MC. and 50 to
225 MC., for i-f and r-f alignment. The mark­
er generator must provide an accurate (crystal
calibrated) frequency of 4.5 MC. for audio i-f
alignment, and accurate frequencies from 21.25
MC., to 25.75 MC., for video i-f alignment.
The required r-f requencies from 50 to 225
MC., as tabulated below, may be provided by
a calibrated signal generator or a heterodyne
frequency meter with crystal calibrator.
2) Output of at least 0.1 volt, with an attenuator
for adjustment of output.
GENERATOR FREQUENCIES: (Table IV ).
d.
e.
-------- 4------ V V \ /------------ -
120
USE CARBON RESISTORS ONLY.
Figure 5-5— Generator Matching Network
VAC U U M -TU B E V O L T M E T E R :
1) A diode .probe for high-frequency measure­
ments is desirable.
2) High input impedance with provision for low-
voltage measurement (three or five volt scale).
O SC ILLO SC O PE :
1) Vertical input should be provided with a cali­
brated attenuator and low-capacity probe.
2) Flat vertical amplifier frequency response, with
good low frequency response.
3) Adequate vertical sensitivity.
SCOPE D E T E C T O R : Required for alignment of
over-coupled first i-f T l. See figure 5-6.
TO TEST POINTS
IN RECEIVER
(KEEP LEADS SHORT)
Figure 5-6— Scope Detector Network
7. ALIGNMENT—
a. A U D IO I-F A L IG N M E N T :
1) Disconnect the antenna and remove the chas­
sis from the cabinet. Use an adaptor line cord
to operate the receiver.
2) Set the C O N T R A ST control at the center of
rotation and retain at this setting for all i-f
adjustments.
3) The waveforms shown in the response curves
may be inverted depending on the number of
amplifying stages in the vertical amplifier of
the scope being used.
4) When the marker signal is coupled in parallel
with the sweep generator, the signal should be
unmodulated and attenuated so that only a
small pip is visible. Use an accurate, crystal-
controlled marker generator.
5) Connect the sync sweep voltage from the sweep
signal generator to the horizontal input of the
scope for horizonal deflection. ^
6) Refer to figure 5-7 for location of alignment
points; figure 5-3 for the schematic diagram.
7) Set the receiver to Channel 3.
Scanned by mbear2k - Jan 20121/17