Jvc RX 750VBK Service Manual

Page 1

NFC/WC (gm) 88L 13¢)

.Jvc
SERV CE MANUAL

if COMPUTER CONTROLLED STEREO RECElVER
MODEL NO. RX-750VBK

5333353553: Il-TT 4:;ié-Inl -_ " .-

T Contents

Safety Precautions ............................................... 1'2 internal Block Diagrams of Major ICs ...................... i-38
Instmcrion Bonk ........................................ 173 Parts List ............................... Separate-Volume insertion

' Technical ExpianarionSA 1729 Block Diagram ........ ,. lnsenion
Removal Procedures 1-33 Connection Diagrams i .. Insanion
Adjusrmem Procedures Schematic Diagrams

l1) FM/AM Tuner PAC. Board
(2] Power Amplifier P.C. Board
Functions of le on me Pra-Ampifler PC Board

1734 (1) Tuner Seciim
1-35 l2] Logic Section
H36 (3) Pre-Arnplilier Section

Insertion

.i Insertion

Insertion

Handling Precautions Of LCD Panels. 136 (4) Power Amplifier Section Insertion
Servicing Method for AWG #20 Wires Schematic Diagram of Remote-comm .............. 1-47
with Clamping Terminals ................................... 137
i
No. 2581

Apr. 1 987

Page 2

RX-750VBK

Safety Precautions

1.

S

1-2

The design of this product contains special hardware and
many circuits and components specially for safety pur-
Poses.

For continued protection, no changes should be made to
the original design unless authorized in writing by the
manufacturer. Replacement parts must be identical to
those used in the original circuits. Service should be
performed by qualified personnel only,

. Alterations of the design or circuitry of the product

should not be made. Any design alterations or additions
will void the manufacturer's warranty and will further
relieve the manufacturer of responsibility lor personal
injury or property damage resulting therefrom.

Many electrical and mechanical parts in the product
have special safety-related characteristics. These charac-
teristics are often not evident from visual inspection nor
can the protection afforded by them necessarily be ob-
tained by using replacement components rated for
higher voltage, wattage, etc. Replacement parts which
have these special safety characteristirs are identified in
the_ Darts list of the service manuaL Electrical compo-
nents having such features are identified by shading on
the schematics and by (A) on the pans list in the
service manual. The use of a substitute replacement
which does not have the same safety characteristics as
the recommended replacement part shown in the parts
list in the service manual may create shock, fire, or other
hazards.

, The leads in the products are routed and dressed with

ties, clamps, tubings, barriers and the like to be sepa-
rated from live parts, high temperature parts, moving
parts and/or sharp edges for the prevention of electric
shock and tire hatard.

when service is required, the original lead routing and
dress should be observed, and it should be confirmed
that they have been returned to normal, after revasserrihl~
mg.

(No. 2991)

5. Leakage current check

(Electrical shock hazard testing)

After reassembling the product, always perform an

isolation check on the exposed metal parts of the

product (antenna terminals, knobs, metal cabinet,

screw heads, headphone jack, control shafts, etc.) to be

sure the product is safe to operate without danger of

electrical shock.

Do not use a line isolation transformer during this check.

0 Plug the AC line cord directly into the AC outlet.
Using a Leakage Current Tester", measure the
leakage current from each exposed metal part of the
cabinet, particularly any exposed metal part having a
return path to the chassis, to a known good earth
ground. Any leakage current must not exceed 0.5
ACir.rn.s.).

0 Alternate check method
Plug the Ac line cord directly into the AC outlet.
Use an AC voltmeter having 1,000 ohms per volt or
more sensitivity in the lollowing manner. Connect a
1.500 I! 10 W resistor paralleled by a 0,15pF AC~
type capacitor between an exposed metal part and a
known good earth ground.
Measure the AC voltage across the resistor with the
AC voltmeten
Move the resistor connection to each exposed metal
part, particularly any exposed metal part having a
return path to the chassis, and measure the AC
voltage across the resistor. Now, reverse the plug in
the AC outlet and repeat each measurement. Any
voltage measured must not exceed 0.75 V AClr.m.s,).
This corresponds to 0.5 mA AClr.m.s.).

~ AC VOLTM ETE R
Ed mums tooo ohms/volt,
or more sensitivity.)

O-

ovnucrwe

Place this probe
on each exposed
metal part

race it now

Good Earth Ground

Page 29

Technical Explanations

Among the various LSIs adomed on this modeL explanations are made in this Section especially on the two types of LSls 65*
signed to SEA control by the computer. These two LSIs are LC7522 (Symbol No. lCSOSl and LC7560 (Symbol No, |C401|.

I Terminal Layout Diagram

,.n~~~__25223fi
noonowma>988>82,

0;.- L5 5 350595357 56555L53525ImALSB.-¢y

.
-V-
Vnd- . 28 inc. D7 -9 L7-t-ls
4'? 21le Due: L5H
lNlaJ 26am: Dahg are.
l7 0/. 25...? Dlo-S Aim-4,
«s «as new: Dn~-6 L)<-l:
2.5 as 23...;5 g, Cx-7 «2--h
l H 4- 7 220 M I C: A: msso mam.
I: «5 § you ca-L-s 50-min
l. g 3 an an «-m asaAs
ll «10 4 199.: cs<--n 33-h
r:5u- H mavsS cs ._2 37-41
YESII --12 I7--CLK C7 u 36--As
5-- l3 Iaem c. ~-u 25 --As
Ver-w ISy-Vcc c, <-5 34 ->A.
5 n
Cmfin T If T If]; 2: 2L 25 25 27 23 25 )0 av 32 A:
séagaaaflsaaészq
l Interior Block Diagram
'_ ___________
| LC'ISZZ 1|
{ Resislor Network _ Resistor erwqu :
l Analog Swilch Analog Switch |
l |
n H
l7 l2
[3 l3
l4 l4
5 l5
45 _ 16
H 2 {7
E I
O
(23:6 ' 0 Shin Register YEST?

I

I

l
L - $666- - --I
VdstsVechc

(N0. 2991] 1-29