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COMPUTER:RADIO SHACK® TRS-80

MODEL 26-3002

TECHNICAL SERVICE DATA FOR YOUR COMPUTER

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MODEL 26-3002

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PRELIMINARY SERVICE CHECKS

This data provides the user with a time-saving service tool

which is designed for quick isolation and repair of Com-puter malfunctions.

Check all interconnecting cables for good connection and

correct hookup before making service checks.

Disconnect all peripherals except the Monitor from the

Computer to eliminate possible external malfunctions.

Replacement or repair of the power supply board, main

board, keyboard, or connectors may be necessary after the

malfunction has been isolated.

TEST EQUIPMENT AND TOOLS

TEST EQUIPMENT TOOLS

Digital Volt/Ohm Meter

Logic Probe

Frequency Counter

TV Monitor

Low Wattage Soldering Iron

Desoldering Equipment

Switch Cleaner (non spray type)

Phillips Screwdriver

Small Flat Blade Screwdriver

IC Insertion and Removal Tools 14, 16, 24, and 40 pin

Alignment Tools GC Electronics: 9440

REPLACEMENT PARTS AND DESCRIPTION

IDENT PART NO. DESCRIPTIONCR12 ADX1474 Diode, 1N5401

CR13 ADX1474 Diode, 1N5401

F1 AHF1185 Fuse,.7A @ 250V

K1 AR8130 Relay

T1 ATA0856 Power Transformer

U1 AXX3051 IC, MC6809EU2 AMX4584 IC, MC14050BU3 IC, SCM90590PU4 IC, MC6821PU6 IC, SN74LS273NU7 IC, MC6847PU8 IC, MC6821PU9 AMX4585 IC, MC14529BU10 IC, SN74LS783NU11 IC, SN74LS138NU12 IC, MC1372PU13 IC, MC1723CPU14 IC, LM339NU15 IC, MC1741CPU20 IC, RAM MK4116N-3GPthru

U27

U28 IC, SCM90522P

&M*£Ww9r*Howard W. Sams & Co*, Inc.

4300 West 62nd Street, P.O. Box 7092, Indianapolis, Indiana 46206 U.S.A.

The listing of any available replacement part herein does not

constitute in any case a recommendation, warranty or guaranty by

Howard W. Sams £ Co. , Inc. , as to the quality and suitability of such

replacement part. The numbers of these parts have been compiled

from information furnished to Howard W. Sams 8 Co., Inc., by the

manufacturers of the particular type of replacement part listed.

Reproduction or use, without express permission, of editorial or pictorial

content, in any manner, is prohibited. No patent liability is assumed with

respect to the use of the information contained herein.

© 1986 Howard W. Sams & Co., Inc.


Printed in U.S. of America. 85CC14951 DATE 1-86

PRELIMINARY SERVICE CHECtCS (Continued)

TVMONITOR

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INTERCONNECTING DIAGRAMRADIO SHACK TRS-80

MODEL 26-3002

PRELIMINARY SERVICE CHECKS (Continued)

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SERVICE CHECKS

'MATCH THE NUMBERS ON THE INTERCONNECTING DIAGRAM AND PHOTOS WITHTHE NUMBERS ON THE SERVICE CHECKS TO BE PERFORMED.

© COMPUTER DEAD

(A) Check for 18VAC at connectors E1 and E2 and

11.0V at connector E3. If the voltages are miss-

ing check Fuse F1. If Fuse is good check the

windings of Transformer T1 for continuity.

(B) If 1 1 .0V is missing at pin 3 of connector E, checkthe 19VAC winding of Transformer T1 for con-

tinuity and check Diodes CR12 and CR13.

(C) If the voltages are correct at connectors E1, E2and E3, check for 5.0V at TP12. If 5.0V is missing

check the Error Amp IC (U13) by substitution.

(D) If the voltage is not correct at TP12, check the

adjustment of the 5V Adjust Control (R60) (see

"Miscellaneous Adjustments").

(T) MICROPROCESSOR (CPU) OPERATION

(A) Computer is dead. Check for pulses at pins 34

and 35 of the CPU IC (U1). If pulses are missing,

check the Dynamic RAM Controller IC (U10) by

substitution.

(B) If pulses are present at pins 34 and 35 of IC U1,

check for pulses on pins 24 thru 31 of IC U1 while

turning the Computer On. If no pulses appear

check IC U1 by substitution.

(C) If pulses appear on pins 24 thru 31 of IC U1, then

suddenly stop, check RAM IC's (U20 thru U27),

ROM IC (U3) and Expansion ROM IC (U28) by

substitution.

©

©

VIDEO

(A) No video. Check the VDG IC (U7) and Video Mix-

er IC (U12) by substitution.

(B) If IC's U7 and U12 check good, check the adjust-

ment of the Video Level Control (R21) (see Mis-

cellaneous Adjustments).

(C) Dots are missing from the alphanumeric

characters. Check IC U7 by substitution.

(D) Wrong characters appear on the Monitor screen.

Check IC's U6 and U7 by substitution.

COLOR

(A) No color. Check for a frequency of 3.579MHz at

pin 7 of the Dynamic RAM Controller IC (U10). If

the 3.579MHz signal is missing, check IC U10 by

substitution.

(C) Colors are not correct. Check for a frequency of

3.579MHz at pin 7 of IC U10. If the frequency is

not correct, check the adjustment of the Clock

Trimmer (C4) (See "Miscellaneous Ad-justments") and check IC U10 by substitution.

(D) If the frequency is correct at pin 7 of IC U10,


(s) SOUND

©

(A) No sound. Type in and run the following Basic

program:

10 SOUND 200,200: GOTO 10

Check for pulses at pin 3 of the RF Modulator. If

pulses are present, check the adjustment of the

Sound Coil (L4) (See "Miscellaneous Ad-

justments").

(B) If pulses are not present at pin 3 of the RFModulator, check for pulses at pin 14 of the

Analog Multiplexer IC (U9). If pulses are present,


(C) If pulses are not present at pin 14 of IC U9, check

for pulses at pins 4 thru 9 of the PIA IC (U4). If

pulses are present, check the Buffer IC (U2) by

substitution. If pulses are missing check IC U4by substitution.

KEYBOARD

(A) Keyboard is dead. Check the Keyboard Connec-

tor (P6) for good connections.

(B) If the Keyboard Connector (P6) checks good,

check for pulses at pin 11 of ICU11. If pulses are

missing, check IC U11 by substitution.

(C) If pulses are present at pin 11 of IC U11, check

the PIA IC (U8) by substitution.

(D) One key is erratic. Clean the contacts of the bad

key and recheck the operation of the key.

(E) A group of keys do not work. Check the Key-

board Connector (P6) for good connections and


(F) More than one letter appears on the Monitor

screen when a key is pressed. Check for shorted

keys or keys that are stuck down.

(B) If the 3.579MHz signal is good, check the Video

Mixer IC (U12) by substitution.

IV


SERVICE CHECKS (Continued)

©

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CASSETTE

(A) Cassette motor will not run or runs all the time.

Check Relay K1 contacts from pin 1 to pin 3 of

connector P5. Check for continuity while saving

or loading a program from tape if the cassette

motor will not run. Check for a short (contacts

stuck) if the cassette motor runs all the time.

(B) If Relay K1 checks good, check the PIA IC (U4) by

substitution.

(C) Programs can not be saved to tape. Check the

PIA IC (U4) and Buffer IC (U2) by substitution.

(D) Programs can not be loaded from tape. CheckIC's U4 and U14 by substitution.

JOYSTICKS

(A) Joystick does not work. Type in and run the

following program:

10 FORX = 0TO320Y = JOYSTK(X)

30 NEXT X: GOTO 10

While the program is running check for pulses at

pins 19 and 39 of the PIA IC (U8). If pulses are

missing, check IC U8 by substitution.

(B) If pulses are present at pins 19 and 39 of IC U8,check for pulses at pin 11 of the Decoder IC

(U11). If pulses are missing, check IC U11 bysubstitution.

(C) If pulses are present at pin 11 of IC U11, checkfor pulses at pins 4 thru 9 of the PIA IC (U4). If

pulses are missing, check IC U4 by substitution.

(D) If pulses are present at IC U4, check for pulses at

pin 15 of IC U2, If pulses are missing, check IC

U2 by substitution.

(E) If pulses are present at IC U2, check for a varyingvoltage at pi 9 of the Analog Multiplexer IC (U9)

while operating the joystick. If the voltage doesnot vary, check IC U9 by substitution.

(F) If the voltage varies at pin 9 of IC U9, check ICU14 by substitution.

(G) Joystick buttons do not work. Check thejoystick button switches for continuity andcheck the joystick Connectors (P3 and P4) for

good connections.

(H) If the joystick buttons and connectors check —good, check PIA IC (U8) by substitution. q

OSERIAL I/O PORT m

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io(A) Serial port does not work. Check the PIA IC (U4) 9

and IC's U14 and U15 by substitution. goto

MISCELLANEOUS ADJUSTMENTS

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5V ADJUST RF MODULATOR

Connect the input of a voltmeter to TP12. Adjust the 5V Ad-

just Control (R60) for a voltage of 5.0V at TP12.

CLOCK ADJUST

Connect the input of a frequency counter to pin 13 of the

Dynamic RAM Controller IC (U10). Adjust the Clock Trim-

mer (C4) for a frequency of 894.886kHz.

Connect the Computer to a TV Monitor and set the TV andChannel Select Switch (S3) to the same channel (channel 3

or 4). Type in and run the following Basic program:

10 SOUND 200,2: GOTO 10

Adjust the Channel Coil (L5) for best picture and sound andadjust the Sound Coil (L4) for best sound with minimumnoise.


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VII


PREVENTATIVE MAINTENANCE

ENVIRONMENT

Computers perform best in a clean, cool area that is below 80 degrees Fahrenheit and free of dust and smoke particles. Eventhough home Computers are not affected by cigarette smoke as much as commercial Computers are affected, it is better tomaintain a smoke-free area around the Computer. Do not block cabinet vents of any of the Computer system; Computer,Monitor, Printer, or other power devices.

ELECTRICAL POWER

Variations in the line voltage can affect the Computer. Try to avoid these fluctuations by using an AC receptacle that is on apower line not used by appliances or other heavy current demand devices. A power-surge protector, power-line conditioner, ornon-interruptable power supply may be needed to cure the problem. Do not switch power On and Off frequently.

KEYBOARD

Liquids spilled into the Keyboard can ruin it. Immediately after a spill occurs, disconnect the Computer power plug from ACpower outlet. Then, if circuitry or contacts are contaminated, disassemble the Keyboard and carefully rinse the Keyboardprinted circuit board with distilled water and let it dry. Use a cotton swab to clean between the keys. Use a non-abrasive con-tact cleaner and lint-free wipers on accessible connectors and contacts.

DISK DRIVES

Clean the read/write heads of the Disk Drives about once a month or after 100 hours usage. Use only an approved head clean-ing kit.

Handle carefully to preserve proper disk head alignment. A sudden bump or jolt to the Disk Drives can knock the disk head outof alignment. If the disk drive must be transported, place an old disk in slot and close door during transport.

Store disks in their protective covers and never touch the disk surface. Observe the disk handling precautions usually foundon the back of disk protective covers.

PRINTERS

Carefully vacuum the Printer regularly. Wipe surface areas clean using a light all-purpose cleaner. Do not oil the machine.The oil will collect abrasive grit and dust. The dust will act as a blanket. This can cause components to overheat and fail.

STATIC ELECTRICITY

Static electricity discharge can affect the Computer. In order to minimize the possibility, use anti-static mats, sprays, toolsand materials, and maintain good humidity in the Computer environment.

MONITOR

Use an isolation transformer with any Monitor that does not come as part of the system since some Monitors use a HOTchassis (chassis connected to one side of the AC line). The face of the Monitor should never be left on for long periods of timeat high brightness level except when pattern is being changed periodically. Use caution when cleaning anti-glare screens, topreserve the glare-reduction feature.

VIII

5j"/Mf COMPUTERFACTS"RADIO SHACK TRS-80

MODEL 26-3002

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PRELIMINARY SERVICE CHECKSENCLOSED

INDEX

SAFETY PRECAUTIONSSee page 18.

Page

Block Diagram 6

Disassembly Instructions 7

General Operating Instructions 7

GridTrace Location Guide 5

IC Pinouts and Terminal Guides 19

Line Definitions 17

Logic Chart 15,16

Miscellaneous Adjustments 7

Parts List 11 thru 14

PagePhotos

Main Board 3,4,21,22

Power Supply Board 20

Safety Precautions 18

Schematics 2,23,24,25

Schematic Notes 17

Test Equipment 8

Troubleshooting 8,9,10

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SAMS* Howard W. Sams & Co., inc.


The listing of any available replacement part herein does not

constitute in any case a recommendation, warranty or guaranty by

Howard W. Sams & Co., Inc., as to the quality and suitability of such

replacement part. The numbers of these parts have been compiled

from information furnished to Howard W. Sams S Co., Inc., by the

manufacturers of the particular type of replacement part listed.

Reproduction or use, without express permission, of editorial or pictorial

content, in any manner, is prohibited. No patent liability is assumed with

respect to the use of the information contained herein.

© 1986 Howard W. Sams & Co., Inc.


Printed in U.S. of America. 85CC1 4951 DATE 1 -86

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GridTrace LOCATION GUIDE

C1 C-24 C78 E-8 R24 E-8 U13 N-9C2 H-11 C79 F-8 R25 G-10 U14 F-10C3 J-21 C80 C-11 R26 H-10 U15 D-8C4 L-21 C81 B-10 R27 C-10 U16 L-19C5 F-21 C82 D-12 R28 D-10 U17 0-7C6 F-15 C83 F-24 R29 D-10 U18 N-3C7 0-2 C84 E-15 R30 1-10 U19 N-1C8 P-28 C85 1-23 R31 G-11 U20 0-24C9 L-1 CR1 C-24 R32 G-11 U21 0-27C10 M-13 CR2 K-21 R33 H-11 U22 0-26C11 N-11 CR3 D-24 R34 H-11 U23 0-23CI 2 C-13 CR4 H-11 R35 1-11 U24 0-22CI 3 E-24 CR5 C-10 R36 1-11 U25 0-20C14 P-11 CR6 D-10 R37 E-10 U26 0-19C15 M-6 CR7 D-11 R38 E-10 U27 0-18C16 M-10 CR8 E-17 R39 E-10 U28 F-1

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C17 L-2 CR9 F-11 R40 D-10 U29 M-14C18 M-1 CR10 F-11 R41 G-11 X1 M-21CI 9 P-9 CR11 1-1 R42 G-11C23 N-23 CR14 0-8 R43 K-21C24 1-13 CR15 N-2 R44 E-18C25 H-13 CR16 1-13 R45 D-22C26 F-15 CR17 N-9 R46 C-23C27 0-16 CR18 G-11 R47 C-13C28 M-1

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El F-1 R48 H-10C29 N-17 E2 G-1 R49 1-10C30 E-18 E3 H-1 R50 C-8C31 0-18 E4 J-1 R51 G-10C32 0-18 E8 L-7 R52 H-10C33 N-20 J1 P-15 R53 G-10C34 H-20 J2 N-15 R54 H-10C35 0-21 J3 P-16 R55 G-10C36 0-9 J4 L-1 7 R56 H-10C37 L-6 J5 K-17 R57 L-20C38 N-2 J6 K-23 R58 0-9C39 0-21 J7 L-5 R59 M-9C40 C-24 K1 D-11 R60 P-12C41 E-15 L2 E-13 R61 0-12C42 F-15 L3 E-13 R62 0-12C43 G-13 L4 D-17 R63 N-11C44 J-23 L5 B-19 R64 N-10C45 0-24 PI G-26 R65 N-10C46 C-24 P2 B-9 R66 M-1

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C47 N-25 P3 B-7 R67 N-1C48 0-26 P4 B-4 R68 H-20C49 0-26 P5 B-11 R69 H-13C50 E-22 P6 0-14 R71 E-12C51 L-20 01 D-14 R72 1-20C52 H-9 02 K-9 R73 L-2 2C53 M-21 03 L-11 R74 M-23C54 C-3 04 E-11 R75 L-2 3C55 C-3 R1 D-24 R76 M-26C56 C-5 R2 D-24 R77 M-26C57 B-5 R3 E-24 R78 N-26C58 C-8 R4 E-23 R79 N-27C59 E-23 R5 1-20 R80 1-18C60 1-16 R6 E-16 R82 D-22C61 P-17 R7 1-20 R83 J-23C62 0-17 R8 C-13 SI C-23C63 N-19 R9 D-14 S2 C-2C64 0-19 RIO K-20 S3 B-13C65 0-20 R11 K-20 TP12 0-15C66 N-21 R12 K-20 U1 G-23C67 0-22 R13 K-20 U2 K-19C68 0-22 R14 K-20 U3 F-20C69 N-24 R15 K-21 U4 L-1 7C70 0-25 R16 E-13 U5 C-18C71 0-25 R17 L-21 U6 H-1 7C72 N-27 R18 E-15 U7 G-16C73 K-22 R19 E-15 U8 L-1

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C74 N-15 R20 E-17 U9 H-8C75 M-24 R21 C-14 U10 L-22C76 D-25 R22 1-13 U11 0-16C77 D-24 R23 E-8 U12 F-1

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DISASSEMBLY iNSTRUCTIONS

CABINET REMOVAL MAIN BOARD REMOVAL

Remove seven phiilips screws from cabinet bottom, turn

Computer right side up and lift cabinet top off.

POWER SUPPLY BOARD REMOVAL

Remove three phiilips screws holding power supply board.

Unplug power supply connectors and remove power supply

board.

Remove Power Supply Board and Keyboard. Remove ten

phiilips screws holding Main Board and remove from

cabinet.

KEYBOARD REMOVAL AND DISASSEMBLY

Unplug keyboard from Main Board and remove keyboard

from cabinet. Turn the keyboard upside down and remove21 phiilips screws from the bottom. CAREFULLY lift bot-

tom cover off the keyboard (the keys and contacts are held

in place by the bottom cover and will fall out if the keyboard

is not laying face down.

POWER UP

GENERAL OPERATING INSTRUCTIONS

CASSETTE OPERATION

The Computer will come up in Basic mode when turned Onwith no cartridge in the cartridge slot. If a cartridge is in-

stalled, the Computer will come up running the program in

the cartridge.

RESET

The Computer can be Reset by pressing the Reset Button

(S1) located on the right rear of the cabinet.

BASIC PROGRAMS

A program in Basic can be started by typing RUN and press-

ing the ENTER key. The program can be stopped by press-

ing the BREAK key or the Reset button.

Connect a Cassette Recorder to the Cassette Socket (P5)

on the Computer. The black plug on the cable connects to

the Earphone jack, the large gray plug connects to the Aux-

iliary jack and the small gray plug connects to the RemoteOn/Off jack on the Recorder. To load a program, type

CLOAD, press the Return key, then put the Recorder in Play

mode with the volume turned about halfway up. An S will

appear on the Monitor screen while the Computer searches

for the program. When the Computer finds the program the

letter F will appear on the Monitor screen, then the word OKwill appear after the program has been loaded.

To Save a program to tape, put the Recorder in Recordmode, type CSAVE and press the Return key. The word OKwill appear on the Monitor screen after the program is

Saved.

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MISCELLANEOUS ADJUSTMENTS

5V ADJUST VIDEO LEVEL

Connect the input of a voltmeter to TP12. Adjust the 5V Ad-

just Control (R60) for a voltage of 5.0V at TP12.

CLOCK ADJUST

Connect the input of a frequency counter to pin 13 of the

Dynamic RAM Controller IC (U10). Adjust the Clock Trim-

mer (C4) for a frequency of 894.886kHz.

RF MODULATOR

Connect the Computer to a TV Monitor and set the TV and

Channel Select Switch (S3) to the same channel (channel 3

or 4). Type in and run the following Basic program:

10 SOUND 200,2: GOTO 10

Adjust the Channel Coii (L5) for best picture and sound and

adjust the Sound Coil (L4) for best sound with minimumnoise.

Connect the input of a scope to the emitter of the Video

Amp Transistor (Q1). Set the scope sweep to 20/tSec,

voltage range to 1V, DC input and trigger to negative slope.

Adjust the Video Level Control (R21) for a blanking level of

2.35V (See Figure 1).

2.35V

Figure 1

TEST EQUIPMENTTest Equipment listed by Manufacturer illustrates typical or equivalent equipment used by SAMS' Engineers to obtain

measurements and is compatible with most types used by field service technicians.

TEST EQUIPMENT (COMPUTERFACTS)

Equipment Name8 & K Precision

Equipment No.

Sencore

Equipment No.

SimpsonEquipment No.

OSCILLOSCOPE 1570A,1590A,1596 SC61 454

LOGIC PROBE DP51

LOGIC PULSER DP101

DIGITAL VOM 2830 DVM37,DVM56,SC61 463,467,470,474,467E

ANALOG VOM 277 260-7,160,165,

260-6XL.260-7P,

260-6XLP

ISOLATION TRANSFORMER TR110,1604,1653,1655 PR57

FREQUENCY COUNTER 1803,1805 FC71.SC61 710

COLOR BAR GENERATOR 1211A,1248,1251,1260 CG25.VA62 431

RGB GENERATOR 1260

FUNCTION GENERATOR 3020 420A.420D

HI-VOLTAGE PROBEVOM/DMMAccessory probes

HV-44 HP200 248

00168,00411,00749

TEMPERATURE PROBE TP-28 I R-1 0,00760,00758;

383,389,388

CRT ANALYZER 467,470 CR70

TROUBLESHOOTINGCOMPUTER DEAD

Remove all peripheral equipment that is connected to Com-puter except the Monitor. Turn Computer On. Check the

operation of Computer. If Computer works properly, turn

Computer Off, plug peripherals in one at a time and recheck

operation of Computer until peripheral causing the problem

is found. If Computer does not work with peripherals dis-

connected, check for 5.0V at TP1 2, - 5.0V at TP1 1 and 1 1 .9V

at pin 3 of Voltage Regulator IC (U17). If voltages are miss-

ing, refer to "Power Supply" section. If voltages are cor-

rect, check for pulses on Data pins (24 thru 31) and Addresspins (8 thru 23) of CPU IC (U1). If pulses are missing at any

of the pins, refer to "Microprocessor Operation" section. If

pulses are present, refer to "Video" section.

POWER SUPPLY

Computer is Dead. Check Fuse (F1). If Fuse is bad, checkfor possible shorts to ground at Voltage Regulator IC's

(U17, U18 and U19), Regulator Transistor (Q2) and check for

possible shorted primary or secondary windings onTransformer T1. If Fuse F1 is good, apply 120V AC powerand check for 36V AC from pin 1 to pin 2 and 11.0V.from pin

3 to ground of connector E. If all voltages are missing,

check for open windings on Transformer T1. If 36V AC is

present from pin 1 to pin 2 and 11.0V is missing at pin 3 of

Connector E, check 19V AC winding of Transformer T1 for

possible open circuit and check Diodes CR12 and CR13. If

voltages are correct at Connector E, check for 5.2V at Col-

lector of Regulator Transistor (Q2). If 5.2V is missing, checkvoltages and components associated with pins 2 thru 6 and10 thru 13 of Error Amp IC (U13) and Regulator Transistors

(Q2 and Q3). If voltage reading is not correct at Collector of

Q2, check adjustment of 5V Adjust Control (R60), see"Miscellaneous Adjustments". If voltage is correct at Col-

lector of Transistor Q2, check for - 12.1 V at pin 3 of VoltageRegulator IC (U18). If -12.1V is missing check DiodesCR11 and CR15, Electrolytics C9 and C17 and IC U18. If

- 12.1V is present at pin 3 of IC U18, check for -5.0V at pin

3 of IC U19. If -5.0V is missing, check Resistor R67, Elec-

trolytic C18 and IC U19. If -5.0V is present at pin 3 of IC

U19, check for 11.9V at pin 3 of IC U17. If 11.9V is missing,

check Diodes CR11 and CR14, Electrolytic C7 and IC U17.

MICROPROCESSOR (CPU) OPERATION

Computer is dead, power supply checks good. Use a scopeto check data lines (pins 24 thru 31 of IC U1) for activity. If

there is no activity check operation of reset circuit by

checking logic reading at pin 37 of CPU IC (U1). The reading

should be Low when the Computer is turned On then im-

mediately go High. The logic reading should also be Lowwhenever Reset switch (S1) is pressed. If logic reading is

not correct at pin 37 of IC U1 when Computer is turned On,

check Electrolytic C1, Diodes CR1, CR2 and CR3 and

Resistor R2. If Power On reset works but Reset Switch (S1)

does not work, check Switch (S1), Capacitor C40, Diodes

CR1 and CR3 and Resistor R1. If reset circuit is operating

properly, check for 894.886kHz clock pulses at pins 34 and

35 of IC U1. If clock pulses are missing, check waveform at

pin 5 of the Dynamic Ram Controller IC (U10). If waveform is

missing, check Crystal X1, Capacitor C51, Trimmer C4,

Resistor R43 and IC U10. If waveform is present at pin 5 of

IC U10, check waveforms at pins 13 and 14 of IC U10. If

waveforms are missing at pins 13 and 14 of IC U10, check IC

U10 and Capacitors C73 and C75.

If clock pulses check good at pins 34 and 35 of IC U1 , check

for a logic High at pins 2, 3, 4 and 40 of IC U1. If logic

reading is not correct at any pin, check IC's and com-ponents that are connected to defective pin.

To check for address lines that may be stuck logic High or

Low, connect a Jumper from pin 40 of IC U1 to ground. All

address lines (pins 8 thru 23 of IC U1) should check logic

open. If any address line checks logic Low or High, check

IC's that are connected to defective line. Grounding pin 40

of IC U1 also causes pins 24, 25, 27 and 28 of IC U1 to go

TROUBLESHOOTING (Continued)

logic Low and pins 26, 29, 30 and 31 to go logic High. If any

readings are not correct on pins 24 thru 31 of IC U1, check

IC's connected to pin with incorrect reading.

Computer will come up properly when turned On, if PIA IC

(U8), Analog Multiplexer IC (U9), IC U14 and Expansion ROMIC (U28) are removed. Turn Computer Off and reinstall IC's

one at a time and recheck opertion of Computer until defec-

tive IC is located.

If pulses appear on data pins (24 thru 31) of IC U1 whenComputer is turned On then suddenly stop, check RAM IC's

(U20 thru U27), ROM IC (U3) and Expansion ROM IC (U28).

VIDEO

Colors are not correct. Check for a frequency of

3.57954MHz at pin 7 of Dynmaic RAM Controller IC (U10). If

frequency is not correct, check adjustment of the

14.31818MHz Clock Trimmer (C4), see "Miscellaneous Ad-justments". If correct frequency cannot be obtained by ad-

justing Trimmer C4, check Crystal X1, Capacitor C51,

Resistor R43 and IC U10. If frequency is correct at pin 7 of

IC U10, check waveforms at pins 5 and 7 of Video Mixer IC

(U12). If waveforms are missing or incorrect, check VDG IC

(U7). If waveforms are present, check IC U12.

SOUND

No sound. Type in and run following Basic program. Theprogram produces a continuous tone from Monitor speaker.

No video. Check waveform at emitter of Video Amp Tran-

sistor (Q1). If waveform is present check adjustment of

Video Level Control (R21) and check for 6.1V at pin 2 of RFModulator. If Control R21 is adjusted properly and 6.1V is

present at pin 2 of RF Modulator, check RF Modulator. If

6.1V is missing at pin 2 of RF Modulator, check Resistor

R45. If R45 is good refer to the "Power Supply" section of

this Troubleshooting guide.

If waveform is missing at emitter of Transistor Q1, checkwaveform at pin 12 of Video Mixer IC (U12). If waveform is

present at pin 12 of IC U12, check voltages and componentsassociated with Transistor Q1. If waveform is missing at

pin 12 of IC U12, check waveform at pin 9 of IC U12. If

waveform is present at pin 9 of IC U12, check IC U12.

If waveform is missing at pin 9 of IC U12 check VDG IC (U7).

Dots are missing from alphanumeric characters. Check IC

U7.

Wrong characters appear on Monitor screen. Check for

pulses at pins 2, 5, 6, 9, 12, 15, 16 and 19 of Latch IC (U6). If

pulses are missing at any pins, check IC U6. If pulses are

present at IC U6, check IC U7.

VIDEO GRAPHICS

One or more Graphics modes do not work. Type in and run

following program:

10FORX = 0TO420 PMODE X: SCREEN X

30 NEXT X: GOTO 10

The program continually switches between five Graphics

modes that are available. While program is running, check

for pulses at pins 27, 29, 30 and 35 of the VDG IC (U7). If

pulses are missing, check PIA IC (U4) and Dynamic RAMController IC (U10). If pulses are present, check IC U7.

COLOR

No Color. Check 3.58MHz waveform at pin 33 of VDG IC

(U7). If waveform is missing, check Dynamic RAM Con-

troller IC (U10). If waveform is present at pin 33 of IC U7,

check waveforms at pins 8 and 10 of Video Mixer IC (U12).

The waveform at pin 10 of IC U12 should look like the

waveform at pin 8 with an amplitude of .3V peak to peak. If

waveform is present at pin 8 and missing at pin 10 of IC U12,

check Capacitor C42 and Resistor R18. If waveform is miss-

ing at pin 8 of IC U12, check IC U12.

10 SOUND 200,200: GOTO 10

While program is running, check for pulses at pins 3, 5, 7, 9,

1

1

and 14 of Buffer IC (U2). If pulses are missing, check PIA

IC(U4). If pulses are present at pins 3, 5, 7, 9, 11 and 14 of IC

U2, check for pulses at pins 2, 4, 6, 10, 12 and 15 of IC U2. If

pulses are missing, check IC U2. If pulses are present at

pins 2, 4, 6, 10, 12 and 15 of IC U2, check for pulses at pin 14

of Analog Multiplexer IC (U9). If pulses are missing at pin 14

of IC U9, check Capacitor C52 and Resistors R10 thru R15and R72. If pulses are present at pin 14 of IC U9, check for

pulses at pin 10 of IC U9. If pulses are missing at pin 10 of

IC U9, check for a logic Low at pins 6 and 7 of IC U9. If pin 6

or 7 of IC U9 do not read logic Low, check PIA IC (U8). If

pins 6 and 7 of IC U9 are correct, check IC U9. If pulses are

present at pin 10 of IC U9 check adjustment of Sound Coil

(L4) on RF Modulator, see "Miscellaneous Adjustments".

KEYBOARD

Keyboard dead. Check keyboard Connector (P6) for goodconnections. If connector checks good, check for pulses at

pin 11 of Decoder IC (U11). If pulses are missing, check IC

U11. If pulses are present at pin 11 of IC U11, check PIA IC

(U8).

One key is erratic or dead. Check bad key for continuity. If

key checks bad, clean key contacts and recheck key.

A group of keys do not work. Check keyboard Connector

(P6) for good connections. If connector checks good, check

ICU8.

More than one letter appears on Monitor screen when a key

is pressed. Check for shorted keys or keys that are stuck

down.

CASSETTE

Cassette motor does not turn Off. Check for 0V at pin 39 of

PIA IC (U4). If the voltage is not correct, check IC U4. If

voltage is correct at pin 39 of IC U4, check for 5.0V at collec-

tor of Relay Driver Transistor (Q4). If voltage is not correct,

check Transistor Q4. If voltage is correct at collector of

Transistor Q4, check for possible sticking contacts in Relay

K1 and check Capacitor C80 and Zener Diodes CR9 and

CR10 for possible shorts.

Cassette motor will not turn On. Type in and run the follow-

ing Basic program. The program turns On Cassette Motor.

10 POKE 65313,60

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TROUBLESHOOTING (Continued)

After running program, check for .9V at pin 38 of PIA IC (U4).

If voltage is not correct at pin 38 of IC 114, check IC U4. If

voltage is correct at pin 38 of IC U4, check for .1 V at collec-

tor of Relay Driver Transistor (Q4). If voltage is not correct,check Transistor Q4, Diode CR7 and Relay K1.

Programs can not be saved on cassette. Type in and run thefollowing Basic program which continuously saves itself to

cassette.

10 CSAVE: GOTO 10

While program is running, check for pulses at pins 5 thru 9of IC U4. If pulses are missing at pins 5 thru 9 of IC U4,check IC U4. If pulses are present at pins 5 thru 9 of IC U4,check for pulses at pins 4, 6, 10, 12 and 15 of Buffer IC (U2).

If pulses are missing at pin 4, 6, 10, 12 or 15 of IC U2, checkIC U2. If pulses are present at IC U2, check for a 1 V peak to

peak waveform at pin 5 of Connector P5. If waveform is

missing at pin 5 of Connector P5, check Capacitors C52 andC82 and Resistors R41 and R42.

Programs cannot be loaded from cassette. Inject a 4V peakto peak 1000Hz square wave at pin 4 of cassette Connector(P5). Check for pulses at pin 13 of IC U14. If pulses aremissing, check voltages and components associated withpins 10, 11 and 13 of IC U14. If pulses are present at pin 13of IC U14, check PIA IC (U4).

JOYSTICK

Joysticks do not work. Type in and run the following Basicprogram to check operation of joysticks.

10 FORX = 0TO320N(X) = JOYSTK(X)

30 NEXT X40 PRINT "RIGHT JOYSTICK HORIZONTAL = ";N(0)

50 PRINT "RIGHT JOYSTICK VERTICAL = ";N(1)

60 PRINT "LEFT JOYSTICK HORIZONTAL = ";N(2)

70 PRINT "LEFT JOYSTICK VERTICAL = ";N(3)

80PRINT "RIGHT BUTTON = ";(PEEK(65280) AND 1)

90 PRINT "LEFT BUTTON = "; PEEK(65280) AND 2)

100 FOR t = 1 TO 100:NEXTT:CLS:GOTO 10

The numbers that appear on Monitor screen for joystickhorizontal and vertical positions should vary from to 63while the joystick is being operated. The numbers that ap-pear for the joystick buttons should change to the numberOwhenever the button is pressed.

Check the joystick Connectors (P3 and P4) for good connec-tions. While program is running, check for pulses at pins 19and 39 of PIA IC (U8). If pulses are missing at pin 19 or 39 of

IC U8, check IC U8. If pulses are present at pin 19 and 39 of

IC U8, check for pulses at pin 10 of Decoder IC (U11). If

pulses are missing at pin 10 of IC U11, check IC U11. if

pulses are present at pin 10 of IC U11, check for pulses at

pins 4 thru 9 of PIA IC (U4). If pulses are missing at pins 4thru 9 of IC U4, check IC U4. If pulses are present at pins 4thru 9 of IC U4, check for pulses at pins 2, 4, 6, 10, 12 and 15of Buffer IC (U2). If pulses are missing at pin 2, 4, 6, 10, 12,or 15 of IC U2, check IC U2. If pulses are present at IC U2^check voltage at pin 9 of Analog Multiplexer IC (U9) whileoperating joystick. The voltage should vary between 0V and5V. If voltage does not vary at pin 9 of IC U9, checkCapacitors C54, C55, C78 and C79 and IC U9. If voltagereadings are correct at pin 9 of IC U9, check for pulses at pin

14 of IC U14. If pulses are missing at pin 14 of IC U14, checkIC U14. If pulses are present at pin 14 of IC U14, checkvoltage at pin 8 of IC U14 while operating the joystick. Thevoltage should vary between OV and 5V. If voltage readingis not correct, check Capacitor C52 and Resistors R10 thru

R15 and R72.

Joystick buttons do not work. If right joystick button doesnot work, check for a logic Low at pin 2 of PIA IC (U8) whilepressing right joystick button. If reading is correct, checkIC U8. If reading is not correct, check Coil L2, check pins 3and 4 of Connector P3 for good connections and check joy-

stick button for continuity. If left joystick button does notwork, check for a logic Low at pin 3 of IC U8 while pressingleft joystick button. If reading is correct, check IC U8. If

reading is not correct, check Coii L3, check pins 3 and 4 ofConnector P4 for good connections and check joystick but-

ton for continuity.

SERIAL I/O PORT

Serial I/O port (Connector P2} does not work. Disconnectany equipment connected to serial port and connect ajumper from pin 4 to pins 1 and 2 of Connector P2. Type in

.and run the following Basic program.

10 POKE 65312,0

20 PRINT "0 OUTPUT ON U4.PIN 3"

30 PRINT "PIN 40=";(PEEK(85313) AND 128)

40X = PEEK(65312)

50 PRINT "PIN 10 = ";(PEEK{65314) AND 1)

60 POKE 65312,255

70 PRINT "1 OUTPUT ON U4.P1N 3"

80 PRINT "PIN 40 = ";(PEEK(65313) AND 128)

90X = PEEK(65312)

100 PRINT "PIN 10=";{PEEK(65314) AND 1)

110FORT = 1 TO50:NEXTT:CLS:GOTO10

The program toggles the serial output pin (pin 3) of PIA IC

(U4) back and forth from 1 to and reads the Carrier Detect

pin (pin 40) and RS232 IN pin (pin 10) of IC U4. The programcontinuously prints results on Monitor screen. When a is

output on pin 3, pin 40 should read 128 and pin 10 shouldread 0. When a 1 is output on pin 3, pin 40 should read andpin 10 should read 1. If readings are correct on Monitorscreen, problem may be in equipment that was connectedto port or in software used to operate the port.

If readings are not correct on Monitor screen, check for

pulses at pin 3 of IC U4 while program is running. If pulsesare missing on pin 3 of IC U4, check IC U4, If pulses are

present at pin 3 of IC U4, use a scope to check for pulsesthat swing from - 10V to + 10V at pin 6 and IC U15. If thepulses are missing or are not correct at pin 6 of IC U15check voltages and components associated with pins 1 thru

4 and 6 of IC U15 and check IC U15. if pulses are present at

pin 6 of IC U15, check for pulses at pins 1 and 2 of IC U14. If

pulses are missing at pin 1 or 2 of IC U14 check voltages

and components associated with pins 1 , 2, 4, 5, 6 and 7 of IC

U14 and check iC U14. If pulses are present at pins 1 and 2

of IC U14, check iC U4.

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12

PARTS LIST AND DESCRIPTION (Continyed)

When ordering parts, state Model, Part Number, and Description

ELECTROLYTIC CAPACITORS CAPACITORS

ITEM

No.RATING MFGR.

PART No.

C17thruC19

1 uF 50V ACC105QJTP

ITEM

No.RATING MFGR.

PART No.

C4 9pF-35pF AC-4926

RESISTORS (Power and Special)

ITEM

No.RATING

REPLACEMENT DATA

MFGR.PART No.

NTEPART No.

WORKMANPART No.

R10R11

R12R13R14R15R75

10K \% 1/4W Carbon Film20K \% 1/4W Carbon Film40. 2K M 1/4W Carbon Film80. 6K \$ 1/4W Carbon Film162K \% 1/4W Carbon Film324K 1% 1/4W Carbon FilmRes i stor Network ( 1

)

AN0281BEEAN0306BEEAN0597BEEAN0359BEEAN0385BEEAN0408BEEARX0220

(1) Contains four (4ea) 33 ohms.

COILS (RF-SF)

ITEM

No.FUNCTION

MFGR.PART No.

L2L3

RF Choke (3.3uH)RF Choke (3.3uH)

ACA8059ACA8059

TRANSFORMER (Power)

ITEM

No.

RATINGREPLACEMENT DATA

MFGR.PART No.

NOTESPRI. SEC. 1 SEC. 2

T1 120V AC S

130mA AC18V AC $

50mA AC18V AC i

160mA ACATA0856993-0433 (1)

SEC. 3 SEC, 4 SEC. 5

19V AC a

600mA DC

30

3 2o oS w">go« ^O -JO 31

<POSo

(1 ) Number on unit.

CONTROLS (All waffages 1/2 watt, or less, unless listed)

ITEMNO.

FUNCTION RESISTANCEMFGR.

PART NO.NOTES

R21

R60Video Level+5V Adjust

5001000

AP7156AP0835

13

PARTS LIST AND DESCRIPTION (Continued)

When ordering parts, state Model, Part Number, and Description

FUSE DEVICES

ITEM

NO.DESCRIPTION

MFGR.PART NO.

NOTES

DEVICE HOLDER

F1 .7A % 250VFast-Acting

AHF1185 AFI176

MISCELLANEOUSITEM

PART NAME MFGR.NOTES

No. PART No.

K1 Relay AR81 30 Cassette EnableR73 Ferrite Bead 2643021801R74 Ferrite Bead 2643021801R75 Ferrite Bead 264000301R76 Ferrite Bead 264000301R77 Ferrite Bead 264000301SI Switch S0852 ResetS2 Switch S0851 PowerS3 Switch S9142 Channel SelectXI Crystal AMX2797 14.31818MHz

Keyboard AXX0206 Comp 1 eteKeyboard Cab 1 e AW2589Power Cord AW2587

CABINETS & CABINET PARTS (When ordering specify model, chassis & color)

ITEM PART No.

Cabinet TopCabinet BottomCartridge Door

AZ5844AZ5845ADA0337

WIRING DATAShielded Hook-up Wire Use BELDEN No. 8401 or 8421 (Single-Conductor)

8208 (Two-Conductor)General-use Unshielded Hook-up Wire Use BELDEN No. 8529 (Solid) Available in 13 Colors

8522 (Stranded) Available in 13 Colors300-Ohm Input Lead Use BELDEN No. 822575-Ohm Input Lead Use BELDEN No. 8241

14

LOGIC CHART

PIN PIN PIN PIN PIN PINNO. Ul NO. Ul NO U2 U3 NO. U3 NO. U4 NO. U4

1 L 21 P 1 H P 21 P 1 L 21 P2 H 22 P 2 L P 22 P 2 L 22 H3 P 23 P 3 L P 23 P 3 H 23 H4 H 24 P 4 L P 24 H 4 L 24 H

5 P 25 P 5 L P 5 L 25 P6 L 26 P 6 L P 6 L 26 P7 H 27 P 7 L P 7 L 27 P8 P 28 P 8 L P 8 L 28 P

9 P 29 P 9 L P 9 L 29 P10 P 30 P 10 L P 10 H 30 P11 P 31 P 11 I P 11 * 31 P12 P 32 P 12 L L 12 H 32 P

13 P 33 P 13 * P 13 L 33 P14 P 34 P 14 L P 14 L 34 H15 P 35 P 15 L P 15 L 35 P36 P 36 P 16 * P 16 L 36 P

1? P 37 H 17 P 17 L 37 H18 P 38 P 18 P 18 H 38 H19 P 39 L 19 P 19 L 39 L20 P 40 H 20 P

1

20 H 40 H

PIN PIN PIN PINNO. U6 U7 NO. U7 NO. U8 NO. U8

1 H L 21 P 1 L 21 P2 P P 22 P 2 H 22 H3 P P 23 P 3 H 23 P4 P P 24 P 4 H 24 H

5 P P 25 P 5 H 25 P6 P P 26 P 6 H 26 P7 P P 27 L 7 H 27 P8 P P 28 8 H 28 P

9 P 29 L 9 H 29 P10 L 30 L 10 P 30 P11 P 11 31 L 11 P 31 P12 P P 32 P 12 P 32 P

13 P P 33 13 P 33 P14 P P 34 P 14 P 34 H35 P P 35 I 15 P 35 P16 P P 36 P 16 P 36 P

1? P H 37 P 17 P 37 P18 P P 38 P 18 P 38 P19 P P 39 L 19 L 39 L20 H P 40 P 20 H 40 P

15

LOGIC CHART (Continued)

PIN PIN PIN PINNO. U10 NO. U10 WO U11 NO. U16 U20 U21 U22 U23 U24

1 P 21 P 1 P 1 P L L L L L2 P 22 P 2 P 2 P P P P P P3 P 23 P 3 P 3 P P P P P P4 P 24 P 4 P 4 P P P P P P

5 P 25 P 5 L 5 P P P P P P6 P 26 P 6 H 6 P P P P P P7 P 27 P 7 P 7 P P P P P P8 P 28 P 8 L 8 P H H H H H

9 P 29 P 9 H 9 P H H H H H10 P 30 P 10 H 10 L P P P P P11 P 31 P 11 P 11 P P P P P P12 P 32 P 12 H 12 P P P P P P

13 P 33 P 13 P 13 P P P P P P14 P 34 P 14 P 14 P P P P P P15 P 35 P 15 P 15 P P P P P P16 P 36 P 16 H 16 P L L L L L

17 P 37 P 17 P18 P 38 P 18 P19 P 39 P 19 P20 L 40 H 20 H

PIN PIN PINNO. U25 U26 U27 U28 NO U28 NO U29

1 L L L P 21 P 1 H2 P P P P 22 P 2 L3 P P P P 23 P 3 L4 P P P P 24 H 4 H

5 P P P P 5 L6 P P P P 6 L7 P P P P 7 L8 H H H P 8 P

9 H H H P 9 P10 P P P P 10 P11 P P P P 11 #

12 P P P L 12 *

13 P P P P 13 L14 P P P P 14 H15 P P P P16 L L L P

17 P18 P19 P20 P

16

SCHEMATIC NOTES

-*- Circuitry not used in some versions-— Circuitry used in some versions

e See parts list

4r Groundrrtr, ChaSSIS

<j Common tie point

Waveforms and voltages taken from ground, unless noted

otherwise.

Voltages, Waveforms and Logic probe readings taken with

computer turned On, no keys pressed, unless otherwise

noted.

Waveforms taken with triggered scope and Sweep/Time

switch in Calibrate position, scope input set for DCcoupling on reference voltage waveforms. Switch to ACinput to view waveforms after DC reference is measured

when necessary. Each waveform is 7 cm. width with DCreference voltage given at the bottom line of each wave-

form.

Time in /isec. per cm, given with p-p reading at the end of

each waveform.

Item numbers in rectangles appear in the alignment/ad-

justment instructions.

Supply voltages maintained as shown at input.

Voltages measured with digital meter, no signal.

Controls adjusted for normal operation.

Terminal identification may not be found on unit.

Capacitors are 50 volts or less, 5% unless noted.

Electrolytic capacitors are 50 volts or less, 20% unless

noted.

Resistors are V2W or less, 5% unless noted.

Value in( ) used in some versions.

Measurements with switching as shown, unless noted.

Logic Probe Display

L = LowH = High

P = Pulse

*=Open (No light On)

LINE DEFINITIONS

A0 THRU A15 Address

CART Cartridge Presence Interrupt

CAS Column Address Strobe

CASS MOT Cassette Motor

CASS OUT Cassette Output

CASSDIN Cassette Data Input

CD Status Interrupt Input (RS232C)

CSN Cartridge Sound

CTS Cartridge Select Signal

DO THRU D7 Data

DAO Display Address Ero

E Clock, 1/16 Master Clock, CPU RAM Addressing

EN1 ROM Enable

EN2 ROM Expansion Enable

FIRQ . Fast Interrupt Request, Does Not Maintain Registers

FS Field Sync

H1 Chip Select, PIA CSO and CS1

HALT Halt CPU Input

HS Horizontal Sync

IRQ Interrupt Request

MAO THRU MA6 Memory Address

MDO THRU MD7 Memory Data

NMI Nonmaskable Interrupt

PIAO Peripheral Interface Adapter Ero

PIA1 Peripheral Interface Adapter OneQ Clock, 1/16 Master Clock,

Leads E Clock by Ninety Degrees

R/W Read/Write

RAS Row Address Strobe

RESET Reset

RS232 RS232 Interface System

RS232 IN RS232 Interface System Input

SCS Spare Cartridge Signal, Selects Address Space

SEL 1, SEL 2 PIA Select Outputs, Joy Sticks or SoundSLENB Select Enable, Disables Internal Selection,

Utilities Unused MemorySND Sound Source in Cartridge

VDG CLK Video Display Generator Clock

WE Write Enable

3D>O50)I>O

wO —1O 33

00o

17

SAFETY PRECAUTIONS

1. Use an isolation transformer for servicing.

2. Maintain AC line voltage at rated input.

3. Remove AC power from the Computer before servicing or installing electrostatically sensitive devices. Examples oftypical ES devices are integrated circuits and semiconductor 'chip" components.

4. Use extreme caution when handling the printed circuit boards. Some semiconductor devices can be damaged easily bystatic electricity. Drain off any electrostatic charge on your body by touching a known earth ground. Wear a commercial-ly available discharging wrist strap device. This should be removed prior to applying power to the unit under test.

5. Use a grounded-tip, low voltage soldering iron.

6. Use an Isolation (times 10) probe on scope.

7. Do not remove or install board, floppy disk drives, printers, or other peripherals with power On.

8. Do not use freon-propelled sprays. These can generate electrical charges sufficient to damage semiconductor devices.

9. The Computer cabinet is equipped with vents to prevent heat build-up. Never block, cover, or obstruct these vents.

10. Instructions should be given, especially to children, that objects should not be dropped or pushed into the vents of thecabinet. This could cause shock or equipment damage.

11"

waLTsTr086 the C°mpUter ,0 Wa,er

'!f exP°sed t0 water

.tum the unit off. Do not place the Computer near possible

12. Never leave the Computer unattended or plugged into the AC outlet for long periods of time. Remove AC plug from ACoutlet during lightning storms.

13. Never use liquids or aerosols directly on the Computer. Spray on cloth and then apply to the Computer cabinet. Makesure the Computer is disconnected from the AC power line.

18

SC PSNOUTS & TERMINAL GUIDE?

SN74LS138NMC1372P IDENT

SELECT -<

ENABLE

A ^^vcc

wa

1

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62A Y2

6395

T3

St Y4

V7 vs

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16 1

2

CLOCK OUTPUT

OSCILLATOR

INPUT

DUTY CYCLE

ADJ

RF TANK

SF TANK

RF MODULATOR

OUTPUT

8ND

COLORSINPUT

COLOR REP

INPUT

COLOR AINPUT

CHROMINANCE

INPUT

LUMINANCE

INPUT

CHROMA NODUUTOROUTPUT

IDENT

3C4CSC61=

7Csc

=116

=115

314313312

111

31039

U2,U27TOP VIEW

U3,U28TOP VIEW

U11

DECODER

TOP VIEW

U12

VIDEO MODULATOR

TOP VIEW

MC14529B

SN741S244N

MC1723CP

NC NC

CURRENT FREQUENCY

LIMIT COMPENSATION

CURRENTV*

SENSE

INVE&TIN6VC

INPUT

N0N-INVLRT1N0

INPUTVOUT

VREF VZ

V- NC

Ut3

REGULATOR

TOP VIEW

STRBX VCC

XO S7JBY

XI YO

X2 YI

X3 Y2

A YS

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GNP z

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TOP VIEW

MM116N-3GP

1 VBB SND IS

132

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CAS

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14

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DD2 RP

DOS A/8

DD4 J/S

DOS OK

CM INV

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A 6M0

H3 SMI

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DA6 6H2

DA7 DA4

DAS DAS

VCC DA2

DA9 DAI

DA10 DAO

DA11 DA12

U20 THRU U26

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SN74LS783N

U7VIDEO DISPLAY

GENERATORTOP VIEW

- v^All VCC

A10 A12

AS A13

AB AM

OSC IN A15

OSC OUT Z7

VCLK Z6

DAO 75

HS 24

IS Z3

CAS Z2

RASO Z1

zo

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R/5 SI

AO 32

A1 A7

A2 AS

A3 AS

«HD A4

P3.P4

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MCSB21P

FRONT VIEW

MC680SEP

VSS CA1

PA0 CA2

PA1 1R0A

PA2 irbb

PAS RSO

PA4 RSI

PAS RESET

PAS DO

PA7 01

PBO D2

PB1 03

PS2 D4

PBS 05

PB4 OS

P65 D7

W6 E

PB7 CS1

cm CS2

etc CSO

VCC R/W

VSS HALT

nmT TSC

ifto LIC

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BS AVMA

BA

VCC E

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Al mA2 DO

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A4 02

AS 03

AS 04

A7 OS

AS OS

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A10 A1S

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A12 A13

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