5
TABLE OF CONTENTS
1. SERVICING NOTE
.......................................................... 6
2. GENERAL
........................................................................ 12
3. DISASSEMBLY
3-1. Case and Front Panel .......................................................... 14
3-2. MD Mechanism .................................................................. 14
3-3. Slider (CAM) ...................................................................... 15
3-4. Base Unit (MBU-5A) BD Board ........................................ 15
3-5. SW Board and Loading Motor (M103) .............................. 16
4. TEST MODE
..................................................................... 17
5. ELECTRICAL ADJUSTMENTS
............................... 22
6. DIAGRAMS
6-1. Circuit Boards Location ...................................................... 31
6-2. Block Diagrams
• BD Section ....................................................................... 33
• Main Section .................................................................... 34
6-3. Printed Wiring Board – BD Section – ................................. 36
6-4. Schematic Diagram – BD (1/2) Section – ........................... 37
6-5. Schematic Diagram – BD (2/2) Section – ........................... 38
6-6. Schematic Diagram – Main (1/2) Section – ........................ 39
6-7. Schematic Diagram – Main (2/2) Section – ........................ 40
6-8. Printed Wiring Board – Main Section – .............................. 41
6-9. Schematic Diagram – Panel Section – ................................ 42
6-10. Printed Wiring Board – Panel Section – ............................ 43
6-11. Schematic Diagram – Power Section – ............................. 44
6-12. Printed Wiring Board – Power Section – .......................... 45
6-13. Schematic Diagram – BD Switch Section – ..................... 46
6-14. Printed Wiring Board – BD Switch Section – ................... 46
6-15. IC Block Diagrams ........................................................... 46
6-15. IC Pin Functions ............................................................... 49
7. EXPLODED VIEWS
7-1. Cabinet Section ................................................................... 53
7-2. Mechanism Section (MDM-5A) ......................................... 54
7-3. Base Unit Section (MBU-5A) ............................................. 55
8. ELECTRICAL PARTS LIST
........................................ 56
SAFETY CHECK-OUT
After correcting the original service problem, perform the follow-
ing safety checks before releasing the set to the customer:
Check the antenna terminals, metal trim, “metallized” knobs, screws,
and all other exposed metal parts for AC leakage. Check leakage as
described below.
LEAKAGE
The AC leakage from any exposed metal part to earth Ground and
from all exposed metal parts to any exposed metal part having a
return to chassis, must not exceed 0.5 mA (500 microampers). Leak-
age current can be measured by any one of three methods.
1. A commercial leakage tester, such as the Simpson 229 or RCA
WT-540A. Follow the manufacturers’ instructions to use these
instruments.
2. A battery-operated AC milliammeter. The Data Precision 245
digital multimeter is suitable for this job.
3. Measuring the voltage drop across a resistor by means of a VOM
or battery-operated AC voltmeter. The “limit” indication is 0.75
V, so analog meters must have an accurate low-voltage scale.
The Simpson 250 and Sanwa SH-63Trd are examples of a pas-
sive VOM that is suitable. Nearly all battery operated digital
multimeters that have a 2V AC range are suitable. (See Fig. A)
Fig. A. Using an AC voltmeter to check AC leakage.
AC
voltmeter
(0.75V)
1.5k
Ω
0.15
µ
F
Earth Ground
To Exposed Metal
Parts on Set
