Motorola xp 303 c service manual

Page 1

television MANUAL 68P65I35A38

CHASSIS HTS-458
MODEL XP303C

MOTOROLA service manual

GENERAL INFORMATION

This receiver uses a transistorized
chassis designed for AC line opera-
tion. All circuits are solid state
except for the high voltage rectifier
and CRT,

The chassis is of compact con-
struction and uses an etched board
on which is mounted the major
portion of the circuitry. Sweep and
audio circuits are mounted external
to the board on metal chassis
brackets for better heat dissipation.
A circuit legend and test points on

the board facilitate troubleshooting. TABLE OF CONTENTS

Description Page
The CRT heater is operated at a
ME T
reduced Voltage when the onI/Off ADJUST N S ' ' ' ' ' ' ' ' '
SWitCh is in the off position. This CHASSIS ALIGNMENT PROCEDURE. . . .

. . . . . 8
reduces the warm-up time, keeping CHASSIS PARTS LOCATION 7
the receiver ready to operate when ' ' ' ' ' ' ' ' ' '
turned on, CHASSIS SCHEMATIC DIAGRAM . . . . . . . . 23,24
_ REPIACEMENTPARTSLIST.............20
The transxstor complement consists
of 23 transistors on the chassis SERVICE NOTES . . . . . . . . . . . . . . . . . . . 2
P1 three in the VHF m and TRANSISTOR LOCATION . . . . . . . . . . . . . 3

one in the UH}? tuner. The chassis

uses 13 diodes and one high voltage TRANSISTOR SPECIFICATIONS. . I I . . . . 25
ream P1 the CRT- UHF TUNER ALIGNMENT (KTT-ézz) . . . . 16
UHF TUNER ALIGNMENT (KTT-626) . . . . l8

UHF TUNER REPLACEMENT PARTS

LIST(KTT-622).....................22
ELECTR'CAL SPECIF'CT'ONS UHF TUNER REPLACEMENT PARTS
Power Rating: 60 Watts LIST (KTT-ézé) . . . . . . . . . . . . . . . . . . . . . 22
UHF TUNER SCHEMATIC DIAGRAM
Source: 120 volts, 60 cycle AC (KIT-622) . _ _ _ 17
E 3 8 INTERMEDIATE FREQUENCIES UHF TUNER SCHEMATIC DIAGRAM
2 fig (KTT-626).................... . ..19
.n I
2 .L >< I-F- - - . - . - - - ~ . Video 45~75M° VHF TUNER ALIGNMENT (SCPTT-394) . . . . . . 11
g m a: Sound 41.25Mc
.. a O VHF TUNER REPLACEMENT PARTS
g 2% SoundI.F..............4.5Mc LIST(SCPTT-394)...................22
E 5 VHF TUNER SCHEMATIC DIAGRAM
S (SCPTT-394).......................14
=
R CAUTION MODEL BREAKDOWN CHART
3
2 VHF UHF
; 3 N0 WORK SHOULD BE AT- MODEL CHASSIS TUNER TUNER CRT
TEMPTED ONANEXPOSED TELE-
VISION CHASSIS BY ANYONE NOT xpsoscw Ins-458 SCPTT-394 KTT»622 IZCGP4
FAMILLAR WITH SERVICING PRO- or
CEDURES AND PRECAUTIONS. KTT-ézé

MOTOROLA INC. 9401 WEST G RAN D AVEN U E, FRAN KLI N PARK, ILLINOIS
PART NO. 68P65135A88 4-67 PRICE 65 cents COPYRIGHT 1967 BY MOTOROLA INC. - PRINTED IN USA.

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SERVICE NOTES

ETCHED BOARD CIRCUIT TRACING

The top (component side) of the
chassis board contains a complete
legend of the chassis circuit that
appears on the bottom and identifi-
cation of all components by refer-
ence numbers that are related to
the reference numbers on the sche-
matic diagram. The circuit may be
traced from the top of the chassis
board and all components can be
identified eliminating the need of
making any reference to the bottom
of the chassis board.

The circuit side (bottom) of the
chassis board also contains a com-
plete legend which includes compo-
nent reference numbers, transistor
identification, coil terminals and
the wiring (jumper wires) is traced
in to provide easy circuit tracing
of the wiring that appears on the top
side of the chassis board.

The transistors are identified by
their function as well as the refer-
ence number. The transistor ele-
ments are identified as follows:
E - emitter, E ~ base and 6- col.
lector.

The tracing indicates where the
Wiring (jumper wires) on the top of
the chassis board is connected.

Breaks appear in the wire tracing
to facilitate the identification of
components location. Each wire
trace begins and ends with anarrow
to indicate where it begins and ends.

To further facilitate circuit tracing
of the etched chassis board, aphoto-
graph of the chassis board with the
pertinent test points identified and
related to the schematic diagram is
included in this manual.

The test points on the schematic
diagram are identified descriptively
and/or by numbers and are blocked
in or circled for easy identification.
These test points are also shown on
the chassis board photographs and
serve to pinpoint the physical loca-
tion of the electrical junction or test
point of interest,

All other test points may be easily
located by circuit tracing from a

transistor, coil, etc. or any point
that is readily identified,

CHASSIS REMOVAL

Seven (7) lcrews secure the chassis
to the cabinet. They are located as
follows: three (3) on the tuner
mounting bracket, one (1) at the
upper right hand corner and three
(3) on the bottom of the cabinet.

Removing components from the
etched board is facilitated by the
fact that the circuitry (plating) ap-
pears on one side of the board only
and the component leads are in-
serted straight through the holes and
are not bent or crimped,

It is recommended that a solder ex-
tracting gun he used to aid in com-
ponent removal. A11 iron with a
temperature controlled heating ele-
ment would be desirable since it
would reduce the possibility of dam-
aging the board due to over-heating.

Thenozzle of the soldering gun is
inserted directly over the compo-
nent lead and when sufficiently
heated, the solder is drawn away
leaving the lead free from the copper
plating. This methodis particularly
suitable in removing multi-terminal
components.

COIL SHIELD REMOVAL

The shields on the 1]? input assemb-
ly(L-100, L-lOl, L- 102 and L-103),
the video detector transformer
(L-107 and L-108) and the ratio de-
tector transformer (T-301) are
mounted to the board with spring
clips for ease of removal. The
shields may be removed by care-
fully rocking the shieldwhile pulling
upward. It may be necessary to
pry up shield slightly to start it.
Avoid excessive bending of the
plated board while removing shield.

PICTURE TUBE REPLACEMENT

Use extreme care in handling the
picture tube as rough handling may
cause it to implode due to atmos-
pheric pressure. Do not nick or
scratch glass or subject it to any
undue pressure in removal or in-
stallation. Use goggles and heavy
gloves for protection.

CRT REMOVAL

CRT is removed from the rear of
cabinet.

To remove picture tube, remove
chassis as previously described,
then remove corner screws securing
picture tube to cabinet.

ADJUSTMENTS

FINE TUNING ADJUSTMENT

Rotate the fine tuning knob in either
direction for best picture and sound
on all available channels. Turning
the fine tuning shaft to the right or
left engages the pre-set gears. The
gears, in turn, change the position
of the core in the oscillator coil.
Individual coils are used for each
channel. Therefore, channel pre-
set adjustments can be made in any
sequence.

FOCUSING ADJUSTMENT

To provide for differences in the
picture tube gun structure, a focus
adjustment is provided by three (3)
lugs located on the chassis. They
provide a ground potential point,
a 544+ voltage point and a bootstrap
voltage point. Connect the blue lead
from the picture tube socket to the
lug which provides the best over-all
focus, center to edge of screen. See
top chassis View for lug location.

VIDEO BIAS ADJUSTMENT

The bias on the let video amplifier
is adjusted for the no-signal con-
dition. Proceed as follows:

1. Disable 3rd Ll amplifier, 0-3,
by shorting base and emitter to-
gather.

2. Set contrast control. R- 130, full
clockwise (maximum contrast).

3. Measure and video amplifier,
Q-S, collector voltage and adjust
video bias control for 23V DC onthe
collector. Line voltage should be
set a 122 volts when adjustment is
made.