1952 RCA 21T176 - Early Television Foundation

JCTIONS
ORE ATTEMPTING ALIGNMENT
tl oscillator tube, (V18), from its socket.
of withstanding considerable current drain. Connect the positive end
junction of R95 & R96.
zontal input of the oscilloscope for horizontal deflection.
•JNECT
:OPE
'M
e to pqinKg>.
to chassis.
'
'
ADJUST
Al
A2
A3
A4
REMARKS
Set bias pot. to -IVoIt, Adjust for MINIMUM
deflection. Attenuate signal gen. to maintain
-IVolt reading.
Adjust for maximum deflection. Attenuate
signal gen. to maintain 1 volt reading.
F IG.4
11,
18.
ALIGNMENT IN
If the tuner is operating and requires only touch up alignment the
completely realigned pre-set all adjustments to the approximate
Pre-set A26 so the screw head is approximately 3/8 inch above t
Do not change any adjustments on the antenna matching unit.
Disconnect the coax link from terminal" A" of L24. Connect a 39S2
Connect a clip lead from the tuner AGC terminal, (terminal 3) to
During step 17 the signal generator is connected to the RF Amp.
and the tube replaced in its socket. Connect the generator to the
Set the fine tuning control 30 degrees clockwise from the mechan
Connect the synchronized sweep voltage from the signal generat
DUMMY
ANTENNA
1500MMF
See fig.e
SIGNAL
GENERATOR
COUPLING
High side to pin 7, (grid)
of 6BQ7, (VI). Low side
to chassis.
Across antenna terminal
SIGNAL
GENERATOR
FREQUENCY
Not used
Not used
MARKER
GENERATOR
FREQUENCY
43. SMC
(4001. mod)
227MC
unmod)
CHAN
2
8
A5
A6
19.
183MC
(10MC Swp)
181. 25MC
185.75MC
up. to point
side to chas-
A7,A8
Connect 330S2 resistor across R37, R38 and
terminals 'A1" and V'of M6. Adjust for response
curve similar to fig. I. Attenuate
sweep gen. to maintain . 5 volt peak to peak
response.
20.
Not used
129MC
6
np. thru de-
-obe, (fig. 2)
of6AU6 (V3).
; to chassis.
ASaAlO
Leave 330J3 resistors connected. Connect a
180n resistorbetween pin 5 of V3 and junction
of R29 and C40. Adjust for response similar
to fig. 3.
FIG.5
21.
22.
"
"
8 SMC
(10MC Swp)
Not used
83.25MC
87, 75MC
Not used
up. to point
side to chas-
Remove all damping resistors. Set IF bias
to -6 volts. Check for response curve similar
to fig. 4. If necessary retouch A4 and A5 for
proper response. Retouch A6 only if absolutely
necessary. Incorrect adjustment of A6 will
interfere with trap action.
23.
24.
"
Repeat step 18.
"
85MC
(10MC Swp)
83.25MC
87. 75MC
ator.
25.
Repeat step 19.
ADJUST
A14
REMARKS
Adjust for maximum deflection on VTVM. Adjust signal
gen. to obtain 10 volt reading.
2*. Repeat step 23, If necessary repeat steps 16, 17, and 20 until no fur
27. see Fig. 8 Across antenna terminal. Not used 257MC
13
A15
A16
A17.A18
A19
Adjust for MINIMUM 4001 indication on scope. Repeat
steps 10 and 11.
Check the voltage at poinK^). II the voltage exceeds ±
1. 5 volts, adjust A16 for zero voltage on VTVM between
positive and negative peaks. Repeat adjustment of A15
and A16 until VTVM reads less than 1 1. 5 volts with
A15 adjusted for MINIMUM 4001 indication on scope.
Adjust for maximum amplitude and symmetry as per
Fig. 5.
lent should not be attempted unless it has been definitely established
required equipment cons sts of a sweep generator capable of at least
nch. Misalignment of this unit can cause serious attenuation of the
will not effect the alignm ;nt,
mid be realigned,
of L8 is alignment Poin \Sy, as shown on the schematic.
mp. thru detrobe
to
>, Low side
A17
A18
A19.A20
Adjust for MINIMUM 400^ indication or scope.
Adjust for MINIMUM 400% indication or scope.
Connect a 3000 resistor from Point^to
chassis. Adjust for response curve similar
to Fig. 7. A19 controls the placement of the
shoulder. A20 is adjusted to give maximum
amplitude of .53MC marker consistant with
curve shape shown in Fig. 7 .
Repeat steps 14, 15 & 16 until no further improvement
can be made.
300-r
BALANCED
L-WV
FIG.6
TO 300j
28.
29.
30.
31.
33.
Repeat Step 20
Repeat Step 19
See Fig. 6 Across antenna terminal.
213MC 211.25MC
(10MC swp.) 215.75MC
207MC 205.25MC
(10MC swp.) 209.75MC
201MC 199.25MC
(10MC swp.) 203.75MC
195MC 193.25MC
{10MC swp.) 197.75MC
189MC 187.25MC
(10MC swp.) 191.75MC
183MC 181.25MC
(10MC swp.) 185.75MC
177MC 175.25MC
(10MC swp.) 179.75MC
85MC
(10MC swp.)
79MC
(10MC swp.)
69MC
(10MC swp.)
63MC
(10MC swp.)
83.25MC
87.75MC
77.25MC
81.75MC
67.25MC
71.75MC
61. 25MC
S5.75MC
55.25MC
59.75MC
57MC
(10MC swp.)
32. See Fig. 6 Across antenna terminal. Not used 257MC
Remove 39SJ Resistor and reconnect from
V 251MC
12
245MC
11
239MC
10
233MC 9
227MC 8
221MC
7
129MC 6
123MC 5
113 MC
4
107MC 3
link
101MC
tuner. Recheck
2
step
FM TRAP
If interference from an FM station is encountered adjust the FM
in the area, they should be checked to make sure the trap is not
13
12
11
10
9
8
7
6
5
4
3
2
13
F IG.8
F IG. 3