— 3 —
SAFETY CHECK-OUT
After correcting the original service problem, perform the following
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).
Leakage 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 passive VOM that is suitable. Nearly all battery operated
digital multimeters that have a 2V AC range are suitable. (See
Fig. A)
Parts No.
4-990-651-1
4-990-651-4
4-990-651-5
Model
US model
Canadian model
AEP model
TABLE OF CONTENTS
1. SERVICING NOTE
.......................................................... 5
2. GENERAL
.......................................................................... 8
3. DISASSEMBLY
3-1. Case and Front Panel Assembly ...................................... 9
3-2. Bracket (T), (L) and (R) .................................................. 9
3-3. BD Board ...................................................................... 10
3-4. SUB Chassis ................................................................. 10
3-5. Shutter Assembly .......................................................... 11
3-6. Over Write Head ........................................................... 11
3-7. Slider Complete Assembly ............................................ 12
4. TEST MODE
..................................................................... 13
5. ELECTRICAL ADJUSTMENTS
............................... 16
6. DIAGRAMS
6-1. Brock Diagrams
• BD Section ....................................................................... 21
• Main Section .................................................................... 23
6-2. Circuit Boards Location ................................................ 25
6-3. Printed Wiring Board — BD Section — ...................... 27
6-4. Schematic Diagram — BD Section (1/2) — ................ 29
6-5. Schematic Diagram — BD Section (2/2) — ................ 31
6-6. Printed Wiring Board — Main Section — .................... 33
6-7. Schematic Diagram — Main Section (1/3) — .............. 35
6-8. Schematic Diagram — Main Section (2/3) — .............. 37
6-9. Schematic Diagram — Main Section (3/3) — .............. 39
6-10. Printed Wiring Board — Display Section — .............. 41
6-11. Schematic Diagram — Display Section — ................ 43
6-12. Printed Wiring Board — Switch Section — ............... 45
6-13. Schematic Diagram — Switch Section — .................. 47
6-14. IC Brock Diagrams — BD Section— ......................... 49
6-15. IC Pin Functions ......................................................... 54
7. EXPLODED VIEWS
7-1. Main Section ................................................................. 63
7-2. Front Panel Section ....................................................... 64
7-3. Mechanism Deck Section (1) (MDM-3GC) ................. 65
7-4. Mechanism Deck Section (2) (MDM-3GC) ................. 66
8. ELECTRICAL PARTS LIST
........................................ 67
MODEL IDENTIFICATION
— BACK PANEL —
Parts No.
To Exposed Metal
Parts on Set
0.15
µ
F
1.5 k
Ω
AC
Voltmeter
(0.75 V)
Earth Ground
Fig. A. Using an AC voltmeter to check AC leakage.
