RCA AR-88 Instructions Manual page 13

6SA7 first det., and the Voltmeter to Terminal C on
last I,F transformer (L47, L48). Tune the generator
to about 7 k.c. off I,F resonance and adjust the crystal
phasing control C7S for minimum response.
Adjustment of Crystal Load Circuit - Make con'
nections as for the preceding adjustment.
(a) Place Selectivity switch in Position 3. Rock the
signal generator frequency back and forth
across the I,F resonant frequency and adjust
the crystal load circuit trimmer L3'1 for sym'
metrical round,top curve.
(b) Place the Selectivity switch in Position 4. Rock
the signal generator frequency and adjust trim-
mer C81 for symmetrical curve.
(c) Place the Selectivity switch in Position 5. Ad,
just trimmer C80 rocking the signal generator
as for (a) and (b) above.
The above three adjustments are very critical and
must be made carefully to obtain symmetrical curves.
Adjustment of Wave Trap - A wave trap is con-
nected across the broadcast band antenna primary to
increase the rejection of I·P signal frequencies. With
the range switch on Position I, apply a modulated I·F
signal to the antenna and ground terminals. Adjust
the wave trap trimmer U7 (See Fig. 3) for minimum
output. The wave trap should be adjusted before the
final R-F alignment on No. 1 band, or the antenna
coil alignment may be affected.
R·F Alignment - A signal generator covering a
range from 53 5 k.c. to 32 megacycles, and an output
voltmeter, are required. It is desirable to connect a
speaker across the output terminals. The output volt-
meter should then be connected across the speaker
voice coil. The output impedance is 2.25 ohms. Re·
move the cover from over the R·F unit by loosening
the four knurled screws and lifting off.
Output Meter Connections ...................................... , ............ Across speaker voice coil
Dummy Antenna ................................................................... See chart below
Generator Modulation. . . . . . . . . . . . . . . . . . . . . . . . . • . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 30% at 400 cycles
Position of Tone Control. ........................ " . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Fully clockwise
Position of Antenna Trimmer. . . . . . . . . . . . . . . . . . • . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . .. See chart below
Position of Power-Transmit-Receive Switch ..........•...........................• Position 3 (Rec. Mod.)
Position of Range Switch.. . . . . . . . . . . . . . . . . . . . . . . • . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. See chart below
Position of R·P Gain Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Fully clockwise.
Position of Audio Gain Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Fully clockwise
Position of Noise Limiter and AVC Switch ..........................
< . . . . . . . . . . . . . . . .
Position 4 (A VC)
Position of Selectivity Switch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . • . . . . .. Position 2
LOCATION OF PARTS AND ALIGNMENT ADJUSTMENTS ON CHASSIS
Oper- Range
anon Switch
No. Position Position of Dial
Generator
Frequency
Dummy
Antenna
1 Extreme low end 53 5 200 mmf
2 Extreme high end 1,600 200 mmf
Position
of Antenna
Trimmer
3 Repeat 1 and 2 until extreme end frequencies are as indicated.
4 1 1,500 k.c. 1,500, 200 mmf \ Max. output
5 I 600 k.c. 600 200 mmf Untouched
6 Repeat 4 and 5 until circuits remain in alignment over the band.
7 2 Extreme low end 1,570. 200 ohms
8 2 Extreme high end 4,550 200 ohms.
9 Repeat 7 and- 8 until extreme end frequencies are as indicated.
10 2 4,300 k.c. 4,300 200 ohms Max. output
11 2 1,700 k.c. 1,700 200 ohms UIA:ouched
Trimmer Adjustments for
Max. Peak Output
(See Figures 3 and S)
L51
C16
C37.C59
L2. Ll4, L24
152
C19
C38,C60
L4, Ll6, L26
12 Repeat 10 and 11 until circuits remain in alignment over the band.
13 3 Extreme low end 4,450 . 200 ohms L53
14 3 Extreme high end 12,150 200 ohms C22
15 Repeat 13 and 14 until extreme end frequencies are as indicated.
16
3
11,500 k.c. 11,500 200 ohms Max. output C39, C62
17 3 4,600 k.c. 4,600 200 ohms Untouched L6, Ll8, L28
18 Repeat 16 and 17 until circuits remain in align ment over the band.
*19 4 Extreme low end 11,900 200 ohms L54
20 4 Extreme high end 16,600 200 ohms CH
21 Repeat 19 and 20 until extreme end frequencies are as indicated.
22 4 16,400 k.c. 16,400 200 ohms Max. output C41, C64
23 4 12,100 k.c. 12,100 200 ohms Untouched L8, L19, L29
12
Trimmer
Function
Low end osc.
High end osc.
lst& 2ndR,P
Ant. &
Ist·
and 2ndR-P
Low end
osc.
High end
~sc.
1st &2nd R-P
Ant. & 1st
and 2nd R-P
Low end osc.
High end osc.
1st & 2nd R-P
Ant. & 1st
and 2nd R-P
Low end osc.
High end osc.
Ist&2nd R-P
Ant. & 1st
and 2nd R·F