GE Superadio User manual

Re-typed in HTML format, remaining as faithful as possible to the original.
MODEL
7-2880A
FM/AM
PORTABLE RADIO
FILE TAB 7
CAUTION: THIS MANUAL IS DESIGNED FOR USE BY QUALIFIED ELECTRONIC TECHNICIANS ONLY. CONSUMER
USERS ARE URGED TO CONTACT QUALIFIED FACTORY AUTHORIZED SERVICE FACILITIES FOR REPAIRS.
FEATURES
Tuned RF on FM and AM improves reception
38" swivel whip FM antenna
7 7/8" ferrite rod AM antenna
4 IF tuned circuits on AM
AFC (Automatic Frequency Control) reduces FM drift
AFC defeat switch for fine tuning of adjacent stations
Precision vernier tuning
6 1/2" high sensitivity speaker
700mW RMS audio output
Separate bass and treble controls to personalize sound
Loudness control boosts bass at low listening levels
2-Way power with built-in AC cord
Automatic switching from AC to batteries
SERVICE SPECIFICATIONS
ELECTRICAL 120
9Volts AC, 60 Hz Volts DC Battery
BATTERIES (6) D Size Batteries
TUNING RANGE AM
FM 530 kHz - 1610 kHz 88 MHz - 108.3 MHz
IF FREQUENCIES AM
FM 455 kHz 10.7 MHz
POWER OUTPUT
10% DISTORTION 700 mW RMS Minimum
SPEAKER IMPEDANCE 8 Ohm
SENSITIVITY AM Better than 150 uV/M for
20 dB quieting
FM Better than 25 uV (IHFM
Sensitivity
SELECTIVITY AM 65 dB (Minimu) for 2 ACA
Selectivity
FM 50 dB (Minimum) for 2 ACA
Selectivity
MINIMUM VOLUME
HUM 5 mV or Less
CURRENT DRAIN
IDLE CURRENT AM FM 20 mA Maximum 26 mA Maximum
ALIGNMENT PROCEDURE
AM ALIGNMENT - FUNCTION SWITCH IN AM POSITION
AM Generator - RF Radiated Signal Modulated 30% at 400 Hz
GENERATOR
FREQUENCY RADIO DIAL SETTING INDICATOR ADJUST REMARKS
1. 455 kHz Closed
Output Meter
Across Speaker
T4, T5, T6, T9 Adjust for maximum. Repeat until no further improvement
is noted.
2. 1630 kHz Open C1L Adjust for maximum
3. 510 kHz Closed L5 Adjust for maximum. Repeat steps 2 and 3 until set will tune
to both band end frequencies.
4. 1400 kHz Tune to Signal C1J, C1K Adjust for maximum
5. 580 kHz Tune to Signal T10, L6 Adjust for maximum. Repeat steps 4 and 5 until no further
improvement is noted.
FM ALIGNMENT - FUNCTION SWITCH IN FM POSITION
High Side of FM Sweep Generator thry a 0.04uF capacitor to TP1, Use only enough Marker Signal for Indication.
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GENERATOR
FREQUENCY RADIO DIAL SETTING INDICATOR ADJUST REMARKS
1. 10.7 MHz Open Scope at TP2. Use Pad (See
Figure 1) T1, T2, T3 Adjust for maximum gain and
symmetry. Repeat as necessary.
2. 10.7 MHz Open Scope at TP3. Use Pad (See
Figure 2) T7, T8 Adjust for maximum gain and
symmetrical S-Curve
FMGenerator - Modulated RF Radiated Signal
3. 109.0 MHz Open
Output Meter
Across Speaker
C15 Adjust for maximum.
4. 87.5 MHz Closed L4 Spread or compress coil wind- ings slightly to raise or lower
frequency. Repeat Steps 3 and 4
5. 108.0 MHz Tune to Signal C1G, C1H Adjust for maximum.
6. 88 MHz Tune to Signal L1, L2 Spread or compress coil wind- ings slightly to obtain optimum
alignment. Repeat Steps 5 and 6
FM AFC ALIGNMENT (R17 TRIM POT
1. Tune FM dial to a no signal area near the center of the FM Band (98 MHz).
2. With the AFC switch S2 in OFF position, connect a high impedance voltmeter (Triplett 630-NS or equivalent) to S2 pin A1 and
measure the D.C. voltage. Note: Voltemeter chosen must not cause noise in FM Band which would cause incorrect alignment.
3. Next connect voltmeter to S2 pin A2 and adjust R17 trim pot to the same voltage as measured in Step 2. Accuracy of voltage
adjustment to voltage measured in Step 2 should be better than +/- 5%.
CABINET DISASSEMBLY
Remove seven (7) cabinet back screws including
one (1) located in battery compartment.
1.
Remove Tuning, Treble, Bass and Loudness knobs.2. Depress ON/OFF Power knob to the ON position.
Separate cabinet front from cabinet back at the bottom of
the cabinet, then carefully lift cabinet front upwards to
exit ON/OFF knob. (Note: Failure to depress knob
during this step will cause switch shaft to bend).
3.
TO SERVICE CIRCUIT BOARDS
To simplify servicing, troubleshoot from component side of
circuit board whenever possible, using the component layout
top view. To prevent damage to cabinet front and speaker,
it is suggested that speaker leads be disconnected at speaker
TO SERVICE CIRCUIT BOARDS, Cont'd
terminals and an 8 Ohm external test speaker be connected to
earphone jack while servicing radio.
Chassis mounting bracket with circuit boards and dial
cord stringing assembly can be removed from cabinet back
by removing screws #1 thru #4 (See Illustration)
For gurthur ease of servicing the bottom side of circuit
board, disconnect FM antenna lead at whip antenna.
1.
Removal of IF / Audio board from mounting bracket may
be necessary to remove a defective component from
certain areas of the circuit board. To remove circuit
board, remove five (5) screws, #5 thru #9,
and tilt chassis to expose conductor side of board.
2.
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ALIGNMENT PADS
Click image to see full size version:
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REPLACEMENT PARTS LIST - MODEL 7-2880A
CAT. NO. SYM. DESCRIPTION
CAPACITORS
EA30X78 C1 Tuning Capacitor
EA1BX268 C2,10,18 75pf, 50V (C)
EA18X201 C3,5,6 15pf, 50V (C)
EA18X186 C4,58,59 100pf, 50V (C)
EA18X283 C7,8,9,14,17 820pf, 500V (C)
RT6494 C11 1pf, 50V (C)
EA18X246 C12 47pf, 50V (C)
EA18X273 C13 5pf, 50V (C)
EA30X26 C15 Trimmer
EA18X151 C16,56 22pf, 50V (C)
EA18X301 C19,21,26,27,44 .0047MF, 50V (C)
EA31X187 C20,31 2.2MF, 50V (E)
EA20X79 C22,39 220pf, 500V (C)
EA18X299 C23,28,30,33,35,43 .047MF, 50V (C)
EA18X174 C24, 25 3pf, 50V (C)
EA18X307 C29 .0022MF, 50V (C)
EA18X203 C32 390pf, 50V (C)
EA31X211 C34 4.7MF, 35V (E)
RT5045 C36,37 220MF, 6.3V (E)
EA18X113 C38 8pf, 50V (C)
RT4635 C40,41 470MF, 6.3V (E)
RT5047 C42 220MF, 16V (E)
RT3860 C45,52 .1MF, 50V (P)
EA22X4 C46 .047MF, 50V (P)
EA31X204 C47 1MF, 50V (E)
EA23X2 C48 .1MF, 50V (E)
EA22X17 C49 .0033MF, 50V (P)
EA22X16 C50 .033MF, 50V (P)
EA22X6 C51,54,55 .01MF, 50V (P)
EA31X200 C53 1000MF, 16V (E)
EA18X224 C57 .001MF, 50V (C)
(C) CERAMIC (P) POLY (E) ELECTROLYTIC
COILS and TRANSFORMERS
EA36X144 L1 FM Antenna Coil
RT4722 L2 FM RF Coil
RT5370 L3 Input Choke
RV2291 L4 FM Oscillator Coil
EA35X160 L5 AM Oscillator Coil
EA83X128 L6 AM Antenna
RT5373 L7 Choke Coil
EA61X281 T1 1st FM IF
EA61X282 T2 2nd FM IF
EA61X282 T3 3rd FM IF
EA61X283 T4 1st AM IF
EA61X284 T5 2nd AM IF
EA61X285 T6 3rd AM IF
EA61X162 T7 FM Det. Primary
RS6795 T8 FM Det. Secondary
EA61X178 T9 4th AM IF
EA61X286 T10 AM RF
CAT. NO. SYM. DESCRIPTION
POTENTIOMETERS
RT2410 R17 AFC Bias Trim Pot, 50K
EA49X501 R24 Treble Control, 100K
EA49X501 R25 Bass Control, 100K
EA49X502 R20 Volume Control, 50K
CAT. NO. SYM. DESCRIPTION
TRANSISTORS and INTEGRATED CIRCUITS
Note: When replacing transistors and integrated circuits with
the type specified below, corresponding changes must also be
made.
CAT. NO. SYM. COMPONENT CHANGES
EA15X7244 Q1 R2 (470K)
EA15X7244 Q2 R4 (330K)
EA15X7244 Q3 R7 (270K)
EA15X7244 Q4 R12 (270K)
EA15X7244 Q5 R13 (56K)
EA15X7590 Q6 R14 (15K), R21 (39K)
EA15X8447 Q7 None
EA33X8525 IC1 R1B Omit
MISCELLANEOUS
EA36X4B3 CF-1 Ceramic Filter, 10.7MHz
EA39X328 SW1 FM/AM Switch
EA39X328 SW2 AFC Switch
EA39X196 SW3 Power ON/OFF Switch
EA95X143 LS101 Speaker 6 1/2", 8 Ohm
EA41X42 JK-1 Earphone Jack
5-1082 MS-1 Earphone, 8 Ohm
EA2X50 MS-2 Whip Antenna w/Sleeve
EA66X48 MS-3 Power Cord
RT2988 MS-4 AMP Connector f/Power Cord
EA69X92 MS-5 Tuning Shaft
EA6X348 MS-6 Tuning Drum
RT8129 MS-7 Spring, f/Dial Stringing
RS4675 MS-8 Pulley
RS2618 MS-9 Dial Cord
RS4556 MS-10 Battery Contact, Positive
RT7977 MS-11 Battery Spring, Negative
EA2X196 MS-12 Battery Spring, Neg/Pos.
EA9X418 MS-13 Main Chassis Mtg. Bracket
EA1X751 MS-14 Cover f/Power Cord Strain Relief
EA3X47 MS-15 Mylar Washer f/Handle
RT5361 MS-16 Nut f/Handle End Caps
RV1532 MS-17 Clip f/Whip Antenna
EA1X752 MS-18 Screw f/Bracket
EA1X752 MS-19 Screw f/Tuning Drum
EA1X754 MS-20 Screw f/Handle Caps
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EA88X129 T11 Power Transformer
DIODES and RECTIFIERS
EA57X14 D1, D2
RT5637 D3
EA16X193 D4
EA16X144 D5
CABINET and APPEARANCE ITEMS
EA98X697 CA-1 Cabinet Front w/ Insert
EA4X799 CA-2 Insert f/ Cabinet Front
EA98X698 CA-3 Cabinet Back
EA89X277 CA-4 Grille w/Holder and Insert
EA9X420 CA-5 Holder w/ Insert
EA78X92 CA-6 Handle
EA90X247 CA-7 Crystal
EA89X276 CA-8 Escutcheon
EA9X417 CA-9 Battery Compartment Door
EA6X347 CA-10 Pointer
CABINET and APPEARANCE ITEMS, Cont'd
EA4X798 CA-11 End Cap f/Handle
EA4X797 CA-12 Dial Insert
EA4X800 CA-13 Sleeve F/Whip Antenna
EA43X959 CA-14 Tuning Knob w/Skirt
EA43X960 CA-15 ON/OFF Power Knob
EA43X961 CA-16 Volume Knob w/Skirt
EA43X962 CA-17 Bass Knob w/Skirt
EA43X962 CA-18 Treble Knob w/Shirt
EA3X128 CA-19 Bushing f/Tuning Knob
EA9X419 CA-20 Cup f/AFC and Band Switch
Replacement parts may be ordered from; General Electric Co., Parts and Accessory Yervice, 1900 Bleecker St., Utica, N.Y. 13501
Note: CA and MS references are for factory use only
IMPORTANT
PERFORM THE FOLLOWING SAFETY CHECKS AFTER SERVICING THIS UNIT:
Remove all externally connected test equipment and wires
before safety testing this unit.
1.
Use RT6440 Safety Test Box or construct circuit as shown.2. Plug power cord at unit to be tested into Test Receptacle.3. Switch unit being tested to ON position.4. Connect VTVMacross 1K resistor in test circuit. Set meter on
high (140V AC) scale to avoid meter damage and touch the
following points with Test Probe.
Speaker Grille
Earphone Jack
Whip Antenna
Screw in Cord Compartment One (1)
5.
If meter reading indicates less than 3 volts on all test points, set
meter to low (3V AC) scale and repeat test.
Any reading greater than two tenths (.2) volt, indicates a
pgtential shock hazard. lf this occurs, determine the cause of
the leakage, correct the problem, and repeat safety test.
6.
DIAL CORD STRINGING INSTRUCTIONS
To restring dial cord, it will be necessary to remove chassis
from cabinet as outlined in circuit board servicing instructions.
Diol cord length 39 1/4".1. Set tuning drum fully counterclockwise2. Steps (1 - 11) indicate correct order and direction of dial3.
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cord installation.
Cement dial cord ends.4.
SERVICE SUPPLEMENT
THIS SUPPLEMENT CONTAINS UPDATED OR ADDITIONAL REPLACEMENT PARTS and SERVICE INFORMATION.
PARTS LIST REVISIONS TO DATE
CORRECT
CAT. NO. REF. NO. DESCRIPTION REVISION
EA82X50 MS-2 Whip Antenna Was EA2X50
EA49X520 R17 Trim Pot Was RT2410
EA36X509 L2 FM RF Coil Was RT4722
EA39X254 SW3 Power ON/OFF
Switch Was EA39X196
EA36X71 L8 RF Choke Add to Parts List
CORRECTIONS TO SCHEMATIC
C48 is shown as 47MF On the schematic diagram- Please change to 0.1MF as shown in the Parts List
SERVICE INFORMATION
This service manual contains the unique replacement parts list and partial schematic for the model 7-2880B AM/FM Portable Radio. The
remaining parts, as well as the schematic, wiring diagram, alignment instructions, are the same as those used in the Model 7-288OA. When
servicing this model, also refer to service manual 7-2880A, Pub. #37-6000-79.
UNIQUE REPLACEMENT PARTS LIST
CAT. NO. SYMBOL DESCRIPTION
EA98X728 CA-1 Cabinet Back w/External
Antenna Terminals
EA3X264 MS-1 External Antenna Terminal
EA83X135 L6 AM Antenna
EA13X218 R38 2.2 Megohm Resistor/Special
High Voltage Type
NOTE: CA and MS References are for factory use only
Replacement parts may be ordered from: General Electric Company, 1900 Bleecker St., Utica, N.Y. I3501
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