Kenwood KA 75 Service Manual

Page 1

STEENTEGRA AMPLIFIER H ' 7 ""
KA-75 KENWOOD

TRIOKENW/OOD CORPORATION

SERVICE MANUAL

986-3 PRINTED IN JAPAN
851-1929-00 (0)1475

Knob ass'y Pane! ass'y Metallic cabinet Knob
(K29-2001-04) : B Knob (Button) Potentiometer (A204769-02): B (A01-1481-02) I B (K29-2020-04) : B
(K294444604) : S iK27-1638-04) x2 (R29-5006-05) (A204770-02) : S (Am-131902): S (K292413504) : S

Phc jack (3P) Knob (Button) Knob assy x4 Knob (Button) Knob (Button) 'Foct

(E11 0162415) (K27-O742-14) X2 (K292375414) : B (K274 637-04) (K273i 639-04) (324)161-04)
(K292337604) : S

Binding post Phone jack (8P) Slide switch AC outiet" Power cord bushing

(NOS-012835) (EB-081405) (S31-2113-05) (E034 (J42-0083-05)

Phpno jack (2P) Phone jack (4P) Lock terminal board (8P) Siide switch AC power cord
(EH-023505) (E13-0497-05) (E20-0823-05) (531208305) (E30 -)

*Refer to parts list on page 8.
Refer to specifications on page 5.
Photo is KA-75 (Black version).
S : Silver version.

B : Black version.

Page 2

DISASSEMBLY FOR REPAIR

The soldering iron does not reach |C1 (X09-) even if the
bottom plate is removed, thus remove the left-hand frame.

1. Remove the 2 screws (0) to remove the bottom
plate

2. Remove the 7 screws ( e ) from the frame, and remove
the frame taking care of the c|aws.

3. Solder Ic1 (x094 ( e ).

Page 3

KA

CIRCUIT DESCRIPTION

Description of components

AUDIO (xiie-zzso-io)

Components Application/Function Operation/caudition/Compatibility
4 Driven by IC1 of X13-5350-10 and tUrned on when the input is changed or
01 , 02 For muting
PHONO REC SW is operated. Interchangeable ZSD1302(S).
* O3~06 Final driver
Interchangeable models of these ones are 28A1106 and 2562581.
O7~Q10 Final These have aluminum internal lead wires. while above interchangeable ones
fl have gold wires. Tips of both groups are the same.
Since detection level is affected by dispersion of hFE, a transistor at too high
011 Q12 Portection level cannot be used At present, short-circuiting with output of about 2V can
' (Detection of current) turn on protection. If sensitivity is too high, protection may works because of
inductance of speaker when output is large.
013, 014 For protection of. BIAS There are no interchangeable modelst
. . Constantcurrent transistor operated by DC voltage obtained by detecting and
015, 016 For drivmg meter _ , , .
rectifying output voltage. Interchangeable With common tranSIstors.
Current mirror for drivin meter
017, 018 g g Interchangeable with common transistors.
LED 01 4~6 paints .
019 AVR l+ side) Interchangeable with TO-220 in 40~50W class.
020 AVFl (- side) Interchangeable with TO~220 in 40~50W class.
021 Constant voltage for class A amplifier Resistance to high voltage is necessary.
A thyristor is composed of 022 and 023. Thus, if protection works, they cannot
022, 023 Protection be reset unless power switch is turned off temporarily. Interchangeable with
common transistors.
. See explanation of operation of circuit
024. 025 For drivmg C-MOS for PHONO FIEC
Interchangeable With common tranSistors,
See ex lanat'on of o erat'on of circuit.
026 For driving MUTE for PHONO REC p ' , p ' .
Interchangeable With common transistors.

TONE (X11-225010)

Components Application] Function Operation/00ndion/Compatibility
' Circuit su lied b manufacture is in ufbbm osition e, but out ut
IC1,ICZ ic for 7 band graphic equalizer . pp ~ y , , p . . » p w 9
Composition type is used considering noises.

SWITCH (X1 3-5350-1 0)

Components Appl ication/ F unction Operation/Condition/ Compatibility
D1 D10 EI t tat' t t Used to protect IC1 from outside voltage higher than source voltage.
.. ~ ec ros it: re ec ion
p MA177 etc. or combination of multipurpose diodes may be used.
For rotection of inverse current
D11 p 4 Any one may be used.
of backup capacnor
I F tn v ha a tire
D12 or preven I g o g p Any one may be used.
caused by D11
. . , . _ SEe explanation of operation of circuit. Common transistor may be used,
01 For initializmg , , . t . .
but it must have hFE of about 100. If it is too high. backup period Will belong.
Pins of this model is compatible with LC7815H, but latter cannot be used,
IC1 C-MOS for input selector . . . -
Since its Withstand voltage is low.