Advertisement
To the Service Technician
PRODUCT SAFETY SERVICING GUIDELINES FOR A L L AUDIO AMPLIFIERS AND RADIO RECEIVERS
CAUTION: No modification of any circuit should be attempted.
Service work should be performed only after you are thoroughly
familiar with all of the following safety checks and servicing guide
lines. T o do otherwise increases the risk of potential hazards and
injury to the user.
S A F E T Y C H E C K S
S U B J E C T : Fire & Shock Hazard
1.
Be sure that all components are positioned in such a w a y
to avoid possibility of adjacent components shorts. This
is especially important on those chassis which are trans
ported to and from the repair shop.
2
Always replace all protective devices such as insulators
and barriers after working on a receiver.
3.
C h e c k for frayed insulation on wires including the AC
cord. Also c h e c k across-the-line components for damage
and replace if necessary.
4
All fuses and certain resistors and capacitors which are
of the flameproof type (shaded on the schematic di
agrams and parts lists) must be replaced with
exact
Zenith types to prevent potential fire hazard.
5
After re-assembly of the set always perform an A C leak
age test on the e x p o s e d metallic parts of the cabinet
such as the knobs, antenna terminals, etc. to be sure the
set is safe to operate without danger of electrical shock.
Do not use a line isolation transformer during this test. U s e
an A C voltmeter having 5 0 0 0 ohms per volt or more sen
sitivity in the following manner: C o n n e c t a 1 5 0 0 ohm 1 0
watt resistor, ( 6 3 - 1 0 4 0 1 - 7 6 ) paralleled by a . 1 5 mfd, A C
type capacitor ( 2 2 - 4 3 8 4 ) b e t w e e n a known good earth
ground (water pipe, conduit, etc.) and the e x p o s e d metal
lic parts, o n e at a time. M e a s u r e the A C voltage across
the combination 1 5 0 0 ohm resistor and . 1 5 mfd. capac
itor. R e v e r s e the A C plug on the set and repeat A C volt
age m e a s u r e m e n t s for e a c h e x p o s e d metallic part. Volt
age measured must not exceed 0 . 7 5 volts R M S . This cor
responds to 0.5 m i l l i a m p A C . A n y value exceeding this
limit constitutes a potential shock hazard and must be
corrected i m m e d i a t e l y .
good earth ground
such as the water
pipe, conduit, etc.
place this probe
on each exposed
metallic part.
TABLE OF CONTENTS
Safety Servicing Guidelines and Technical Applications Index
Inside Front Cover
Index to Schematics and Related Drawings
Page 1
Product Features
Pages 2-5
Record Changer Features
Page 6
Tape Unit Features
Page 7
Introduction
Page 8
Product Features
Page 9
General Information
Page 10
Alignment Procedures
Pages 11-15
Disassembly
Pages 16-19
Theory and Application
Pages 20-22
Parts Lists
Pages 24-36
Integrated Circuit Block Diagrams
Pages 38-41
Schematic, Related Drawings and Exploded Views
Pages 43-60
TECHNICAL APPLICATIONS INDEX
Various " H F " series service manuals contain information relating to solid state device theory, operation and circuit applications as
introduced into our products. In addition, service procedures are also explained, if required, in the appropriate service manuals.
Such information has been included in the following service manuals:
HF 18: Theory - Diodes (Including Zener and SCR), Transistors, (PNP, NPN, Darlington, and JFET). Applications - Chassis 29AT24 (JFET FM-RF,
Multiplex, Electronic Touch Switching), Complementary Symmetry, Chassis 11ZT27 (Electronic Filter).
HF 22: Theory - JFET, IGFET, MOSFET, Applications - Dual Gate MOSFET FM-RF, JFET Biplex Detector, Quasi-Complementary Symmetry.
HF 23: Applications - Model C9029/Chassis 15WCA10 Four Channel Decoder.
HF 26: Applications - Chassis 15WDR51 (JFET Meter Circuit, Multiplex IC, Four Channel Decoding).
HF 27: Applications - Model SD2568 Speaker Switching Circuitry.
HF 28: Applications - Model D9013W Allegro Speaker System.
HF 29: Theory — Light Emitting Diodes (LED). Applications - Three Light Tuning (Target Tuning), Multiplex IC.
HF 29S1: Applications — Snap-off Escutcheon and Out Front Chassis Removal, " E " Line Models.
HF 30: Applications — Snap-off Escutcheon and Out Front Chassis Removal, " F " Line Models.
HF 3 1 : Theory and Applications - Chassis 12WGR59 (Ceramic Filters, IF IC, Quadrature Detector, Interstation Muting, PLL Multiplex IC, Audio).
General Product Information — Audio Circuitry (including Two on Two Speaker Matrix, Allegro Speaker Systems), " G " Line Disassembly
Procedures.
HF 32S2: Applications - Four Channel Sound Reproduction Input Vs. Output, Repairing Push Button Switches, Record Changer and Phono Cartridge
Inter Changeability, Chassis 12WGR59 Accessibility.
HF 32: Applications - " H " Line Disassembly Procedures, Part Number Identification, Record Changer and Phono Cartridge Inter Changeability, " H "
Line Allegro Speaker Systems and Repair Procedures.
H F 3 3 : Theory and Applications - Chassis 3WJR52 (Ceramic Filters, IF IC's for AM and FM Quadrature Detector, PLL Multiplex IC, Audio).
General Product Information — Audio Circuitry (including Output IC), " J " Line Disassembly Procedures.
HF 33S1: Applications — " J " Line Allegro Speaker System Repair Procedures.
HF 34: Applications — " K " Line Allegro Speaker Systems and Repair Procedures. General Product Information.
HF 39: Applications - " K " Line Allegro Speaker Systems and Repair Procedures.
A C V O L T M E T E R
Advertisement
