SERVICE MANUAL
MODEL PLUS 4 COMPUTER
OCT. 1984
PN-314001-04
Commodore Business Machines, Inc.
1200 Wilson Drive, West Chester, Pennsylvania 19380 U.S.A.
Commodore makes no expressed or implied warranties with regard to the information contained
herein. The information is made available solely on
an as is basis, and the entire risk as to quality and
accuracy is with the user. Commodore shall not be
liable for any consequential or incidental damages
in connection with the use of the information contained herein. The listing of any available replacement part herein does not constitute in any case
a recommendation, warranty or guaranty as to
quality or suitability of such replacement part.
Reproduction or use without expressed permission,
of editorial or pictorial content, in any matter is
prohibited.
This manual contains copyrighted and proprietary information. No part
of this publication may be reproduced, stored in a retrieval system, or
transmitted in any form or by any means, electronic, mechanical,
photocopying, recording or otherwise, without the prior written permission of Commodore Electronics Limited.
Copyright © 1984 by Commodore Electronics Limited.
All rights reserved.
CONTENTS
Page
Title
SPECIFICA TIONS
••• •••
• • •
••• •
• • •
••••
• •
•••
•
••
• •
••••• •
•••
• • • • • •
OVERVIEW
• • • •
•••
• • •
• ••••
•
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• •
•
•• ••
•
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•
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••••••• •••
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.• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •
2
.
3
• •••
3
.
4
• • •
5
••••
7
.
7
PRODUCT PARTS LIST
CASEWORK
IDENTIFICATION
••
• • •
• •••
•
••
•
••
• • •
•• ••••
•
•••••••••••••• •
• • • • • • • • • • • • • •
••• ••••••
• •
••••
• •
• •••
• •
PCB LAYOUT
PCB PARTS LIST
PCB SCHEMATIC
••
• • • • • •
••••••••••
DIAGRAMS
•
••
• •
• •
• •
• •
••••
•••••••••••
•
•••
• •
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•
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•
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••
• • • •
• • • •
•••••• ••••
••• ••••
• • • •
• • •
•• ••••
• •
RF MODULATOR
RF MODULATOR
CHIPS
251844
LAYOUT
251844
SCHEMATIC
251311
LAYOUT
251311
SCHEMATIC
• •••• •
•• ••••••••••••••
KEYBOARD MATRIX
I.C. PINOUTS FOR UNCOMMON
1
•
• •
9
•••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••
•
•
•••••
•
••••••
• •
• •••••••••
•
••••••••
•
• •••••••••••
• •
•• •••
• •
.
11
••••••••••
11
..
12
.
12
iii/iv
PLUS 4 PRODUCT SPECIFICATION
MEMORY
64K RAM. 60K RAM User accessible for BASIC programs.
ROM
32K ROM Standard (includes operating system and BASIC interpreter) with 32K additional ROM containing the built-in productivity software.
MICROPROCESSOR
7501 Microprocessor
-
.89 or 1.76 MHz clock.
DISPLAY
40 Columns x 25 lines of text.
COLORS
128 Colors (16 colors; 8 luminance levels).
CHARACTERS
Upper & lower case letters, numerals and symbols. Reverse and flashing charachters. All PET graphic
characters.
DISPLAY MODES
Text characters. High resolution graphics. Split screen text/high resolution graphics. Multicolor graphics.
RESOLUTION
320 x 200 Pixels
SOUND
2 Tone generators
or 1 Tone and 1 white noise generator.
VOLUME
8 Volume levels
KEYBOARD
Full size typewriter
style design
KEYS
67 Keys total. 4 Cursor control keys. 4 Programmed (reprogrammable) function keys (up to 8 user
defined functions possible). Color control keys. HELP key. Upper and lower case character set. Graphics
character set.
INPUTS/OUTPUTS
PLUS/4 MODEM (User) port. Serial port. ROM cartridge and parallel disk drive port. 2 Joystick ports.
C 1531 Cassette drive interface port. RF Output-channel
3 or 4. Video output-composite/
chrominance/luminance.
Audio input/output.
Power supply input.
1
PLUS 4 PRODUCT SPECIFICATION (Continued)
FEATURES
Built-in extended BASIC 3.5 - over 75 commands. Built-in Machine Language monitor - over 12
commar.ds. Built-in graphics and sound commands. Screen window capability. Reset button (Warm
start). Built-in integrated productivity software.
PERIPHERALS
C1551 Fast Disk drive, C1531 Datasette, MPS 802 Dot matrix printer, MPS 803 Dot matrix printer,
DPS 1101 Daisy wheel printer, C1802 color monitor.
OTHER PERIPHERALS
C1541
Disk drive, MPS 801 Dot matrix printer, C1702 color monitor.
PLUS 4 OVERVIEW
The Plus 4 system is based on the 7501 microprocessor, an HMOS version of the 6510. Video processing is achieved by the 7360 TED chip. 64K bytes of dynamic RAM are accomplished by 8 (64K
x 1) I.C.'s. (See page ). The system program is contained in 2 (16K x 8) ROMs. The system supports
up to 128K x 8 of ROM banked in 16K sections. By software control, through the 7360, ROM can
be completely banked out and RAM banked in for a true 64K of RAM (minus 256 byte pages), allowing 60,671 bytes available for BASIC.
Keyboard and joystick scanning are accomplished by outputting the row data on the data bus while
addressing a particular register in the TED chip. This will in turn cause the TED chip to latch the column
information.
A standard serial port supports serial bus peripherals such as the 1541 disk drive and the various
serial printers. A cassette port is provided and the expansion port supports ROM cartrdiges. TTL serial
ASCII is intended to drive an RS-232 adapter.
2
PARTS LIST
PLUS/4
TOP CASE ASSY
Top Case
Keyboard, 67 Key, KKR-I
Nameplate
Shield Clip, R
Shield Clip, F
C
C
C
C
C
251453-01
251501-01
251655-01
251855-01
251856-01
C
C
C
C
C
C
251454-01
950157-04
310156-01
310199-01
310197-01
310198-01
C
C
C
C
310196-01
310157
326189-02
904778-01
BOTTOM CASE ASSY
Bottom Case
Foot, Self-Adhesive
Paper Shield
Shield Chip
Shield Plate
Insulation Sheet
ACCESSORIES
Users Manual
Power Supply
RF Cable
Switch Box
C -
Commodore Stock Part
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PARTS LIST PLEASE NOTE:
PLUS/4 PCB ASSEMBLY #310163-01
Commodore part numbers are provided for reference only and do not indicate the
availability of parts from Commodore. Industry standard parts (Resistors, Capacitors,
Connectors) should be secured locally. Approved cross-references for TTL chips,
Transistors, etc. will be available in manual form through the Service Department
in November of 1984. Unique or non-standard parts will be stocked by Commodore
and are indicated on the parts list by a "C".
DIODES (Continued)
INTEGRATED CIRCUITS
Ul
U2
U3
U4
U5
U6
U7
U8
U9-10
U11-18
U19
U20
U21
U22
U23
U24
U25
U26
U27
CR1
(cont.)
CR2
CR11-20
7360 VLSI, Text Dislay (TED)
Sub:
C 251535-01
8360
C 251535-02
7501 Custom Microprocessor
C 251536-01
6551 A (Synertek)
901895-02
74LS08
901521-03
6529B Single Port Interface
C 251640-03
901521-02
74LS04
901522-06
7406
901523-01
555
901521-57
74LS257
901505-01
4164-2 D-RAM
C 251641-02
7700-01 0 PLA
901521-18
74LS139
901521-34
74LS175
901521-22
74LS27
2312B ROM TED Basic
C 318006-01
23128 ROM TED Kernal
C 318005-04
23128 FUNCTION ROM, 3 + 1 LOW
C 317053-01
23128 FUNCTION ROM, 3+HIGH
C 317054-01
6529B Single Port Interface
C 251640-03
Rl
R2
R3
R4
R5
R6
R7
R8
R9
Rl0
R11
R12
R13
I 2SC 1815
I 2SD 880
Tip 29A
2SD 1266
All values are in ohms-1/4 W
5% unless noted otherwise.
4.7K
10K
470K
220K
18K
1.5K
470K
lOOK
1K
1K
12K
10K
lK
R14
R15
R16
R17
R18
R19
R20
R21
R22
R23
R24
R25
240
250
lOOK
1.5K
47K
lOOK
3K
1K
1K
lK
1K
1K
RESISTOR PACK
RP1, 2
RP3,4
3.3K, 6 PIN
68, 8 PIN 4 ISOLATED
902441-29
326149-06
CAPACITORS
902693-01
902694-01 Sub:
902653-01 Sub:
902694-04
DIODES
CR1
Rectifiers DBA20C
251026-03
Zener RD 6.8 EB 900927-01
IN 914 Sub:
900850-16
IN 4148 Taping
251819-21 Sub:
Diode, IN 4148
900850-01
RESISTORS -
TRANSISTORS
01-03
04
Bridge
Sanyo
Diode,
Diode,
Diode,
II
I Bridge Rectifiers S2VB 10 Sindengen
215026-01 Sub:
Bridge Recitifers DBA20B Sanyo
251026-02 Sub:
C1
C2
C3
C4
C5-C6
C7
C8
C9
C10
Cll
Elect
Ceramic
Film
Film
Ceramic
Elect
Elect
Ceramic
Trimmer
Ceramic
0.1 µ,F 25V
0.1 µ,F 25V
0.22 µ,F 100V
0.22 µ,F 100V
0.22 µ,F 50V
2200 µ,F 16V
10 µ,F 16V
0.1 µ,F 25V
40 pF
22 pF 50V
900100-40
251075-06
900150-11
900150-11
900022-01
900101-33
900100-25
251075-06
! 251029-02
251070-14
5
PARTS LIST - PLUS/4
PCB ASSEMBLY #310163-01 (Continued)
MISCELLANEOUS (Continued)
CAPACITORS (Continued)
C12
C13
C14
C15-C16
C17-C18
C19
C20
C21
C22
C23
C24-C26
C27
C28-C29
C30
C31-C32
C33-C40
C41-C51
C100
Ceramic
251071-26
Ceramic
Ceramic
Sub:
Ceramic
Ceramic
Ceramic
Ceramic
Ceramic
Elect
Ceramic
Elect
Elect
Ceramic
Elect
Ceramic
Elect
Ceramic
Ceramic
Sub:
Ceramic
Ceramic
Sub:
Ceramic
Ceramic
220 pF 50V
Sub:
220 pF 50V
150 pF 50V
Sub:
150 pF 50V
0.1 µF25V
0.1 µF 25V
10 µF 16V
0.01 µF 25V
10 µF 16V
0.1 µF 25V
10 µF 16V
1 µF 16V
0.1 µF 25V
10 µF 16V
0.1 µF 25V
10 µF 16V
0.1 µF 25V
0.22 µF 25V
900462-41
251075-01
251075-06
900100-25
251075-01
900100-25
251075-06
900100-25
900100-16
251075-06
900100-25
251075-06
900100-25
251075-06
251075-07
0.22 µF 50V
0.1 µF 50V
900022-01
900020-06
0.1 µF 50V
0.1 µF 50V
9000010-01
900010-20
900463-08
251071-24
FB2-14
FB15-21
FB22-26,
FB28-38,
FB40
FB41-58
FB59
FB60
FB61-63
FB64-65
Ferrite bead
Ferrite bead
325563-01
903025-01
Ferrite bead
325563-01
Ferrite
Ferrite
Ferrite
Ferrite
Ferrite
903025-01
325563-01
903025-01
325563-01
903025-01
EM1,2
EMI Filter
CN1
Connector 4 PIN (power supply)
C 251614-01
Connector 6 PIN DIN (serial bus)
C 903361-01
Connector 7 PIN MINI DIN (cassette)
C 251616-01
Connector 50 PIN Female Edge
(exoab)
C 251630-01
Connector 8 PIN MINI DIN
(joy 1 & 2)
C 251259-01
Connector 8 PIN DIN (audio/video)
325573-01
Connector 18 PIN (keyboard)
C 251841-01
CN2
CN3
CN4
CN5-6
CN7
CN8
bead
bead
bead
bead
bead
251842-01
MISCELLANEOUS
Y1
Y2
SW1
SW2
M1
L1
L2
Crystal 14.31818 MHZ 251081-01
Sub:
Crystal 14.31818 MHZ 251081-02
Crystal 1.8432 MHZ
900555-02
L3,L3
Switch, Rocker
(PC Mount)
Switch, Push Button
C 251587-01
RF Modulator
Sub:
RF Modulator
C 251844-01
C 251260-01
F1
Noise Filter
Line Filter
Sub:
Sub:
Coil Inductor 1.2 uHpt
Sub:
251264-01
906127-01
251701-01
Fuse 250V 1.5A
Fuse Clip
Cartridge Guide
Shield Box
Shield Cap
903556-18
906102-01
310171-01
C310172-01
C 310173-01
901152-01
325570-01
251311-01
C -
Commodore Stock Part
6
14
17
RE.
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5
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KEYBOARD MATRIX
1\
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3
A2
A1
A0
I<J
cj>OI N RDY -IRQ AEC -
1
2
3
4
VCC - 5
A
6
A - 7
A2'- 8
A3i9
A4.- 10
A51- 11
A6,- 12
A7 - 13
A8 - 14
A9 - 15
A1 no. 16
A 11 - 17
A12 - 18
A13 - 19
GND,- 20
~
7501
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
RES
R/W
-
-
-
-
D0
D1
D2
D3
D4
D5
D6
D7
P0
P1
P2
P3
P4
P5
P6
GATE IN
A15
A14
PIN ASSIGNMENT
U2-251536-01
CUSTOM MICROPROCESSOR
VDD CS0 CS1 R/W -
IRQ
MUX
RAS
CAS
cj>0
-
-
COLOR CLK IN K0 K1 K2 K3 K4 K5 K6 K7 -
SYNC VSS -
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
7360
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
-A3
-A4
-A5
-A6
-A7
-A8
-A9
-A10
-A11
-A12
-A13
-A14
-A15
-AEC
-BA
-SND
-D7
-D6
-D5
-D4
-D3
-D2
-D1
-D0
PIN ASSIGNMENT
U1-251535-01
VLSI, TEXT DISPLAY
(TED)
SHIFT LOCK
SW
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TRANSMIT/RECIEVE CHARACTERISTICS
M1 SCHEMATIC ON PAGE 11
PIN
CONFIGURATION
1
2
3
RES
4
5
RXC
XTL 1 - 6
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RTS 8
9
CTS TXD - 10
DTR - 11
RXD - 12
RSQ)- 13
RS1 - 14
VSS
CSQ)
CS1
6551
28
27
26
25
24
23
22
21
20
19
18
17
16
15
CHARACTERTISTICS
TRANSMIT /RECEIVE
CLOCK RATE
TRANSMIT /RECEIVE
CLOCK HIGH TIME
TRANSMIT/RECEIVE
CLOCK LOW TIME
XTL 1 TO TXD
PROPAGATION DELAY
RTS PROPAGATION
DELAY
IRQ PROPAGATION
DELAY (CLEAR)
-IRQ
UNIT
MAX
MIN
-R/W
-Q)2
-D7
-D6
-D5
-D4
-D3
-D2
-D1
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2 MHZ
SYM
*
tCCY
400
-
ns
tCH
175
-
ns
tCL
175
-
ns
too
-
500
ns
tDLY
-
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ns
tlRQ
-
500
ns
(tr, tf = 10 to 30 ns)
*The Baud Rate with External Clocking is:
BAUD RATE
1
16 x T CCY
U3-901895-02
ACIA
SYNERTEK ISYP6551A 12 MHZ
PIN
CONFIGURATION
PIN
CONFIGURATION
FE 171615141312I1 IQ)F7 F6 F5 F4 GND -
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
U19-251641-02
PLA
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-19
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-113
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00-07
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L
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P4
P5
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I
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SINGLE PORT
INTERFACE
1
2
3
4
5
6
7
8
9
10
6529
3 MHz
I
20
19
18
17
16
15
14
13
12
11
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U3, US, U19 PINOUTS ON PAGE 8
PIN
CONFIGURATION
A(JJ -
5
6
A2 A1 - 7
VCC - 8
-vss
(ns)
HM4864-3
200
335
330
20
!-,PD4164-2
200
375
250
28
M5K416NS-20
200
330
275
28
MOSTEK
MK4564N-20
200
345
300
22
901505-01
OKI
MSM3764-20
200
330
248
23
901505-01
HITACHI
HM4864P-3
200
335
330
20
901505-01
MATSUSHITA
(PANASONIC)
MN4164P-20
200
330
275
27.5
901505-01
SIEMENS
HYB4164-3
200
330
150
20
901505-01
SHARP
LH2164-Z1
200
330
248
28
901505-01
HITACHI
HM4864AP-3
200
330
242
20
901505-01
TOSHIBA
TMM4164AP-20
200
330
275
22
901505-01
HITACHI
11 -A4
901505-01
NEC
901505-01
MITSUBISHI
901505-01
10 -A5
9 -A7
R/W CLOCK
GENERATOR
-
(ns)
ACTIVE
(MW)
-A6
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U11 - 18
64K DYNAMIC RAM
901505-01
WE
CYCLES
APPROVED
1
SOURCE
OF SUPPLY
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VENDOR
PART
NUMBER
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CAS CLOCK
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POWER
STANDBY
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ACCESS
TIME
COMMODORE
PART
NUMBER
16
15
14
13
12
1
NC
2
DIN
WE - 3
RAS - 4
....
MEMORY
ARRAY
0
u
•
FUNCTIONAL DIAGRAM
VBB GENER ATOR
PIN
CONFIGURATION
28 -VCC
1
27 -CS3
2
26 -A13
3
25 -A8
4
24 -A9
5
23 -A11
6
7 23128 22 -CS,
21 -A1CIJ
8
20 -CS2
9
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10
18 -D7
D1 - 11
17 -D6
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16 -D5
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15 -D4
GND - 14
NC
A12
A7
A6
A5 A4 A3 A2 A1 ACIJ
U23-318006-01
ROM - BASIC
PIN
CONFIGURATION
NC
A12 A7 A6 A5 A4 A3 A2 A1 ACIJD1
D2
D3
GND
-
1
2
3
4
5
6
7 23128
8
9
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11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
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U24-318005-04
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:
COMPONENT PARTS VALUE: R = n. C = F. L = H
Q3. Q4: 2SC460 OR EQUIVALENT.
Q1. Q2: 2SC1684 OR EQUIVALENT.
03. 04: 1SS 198 OR EQUIVALENT.
02
: 1SS110 OR EQUIVALENT.
01
: 1SS119 OR EQUIVALENT.
p3
~():)p
l
I
I ~!
TERMINALS
NO.
'1
o
"
1
N.C.
2
AUDIO SIG. INPUT
3
+B (+5V)
'--I,
-!1ft
RCA. PHONO JACK
TOP VIEW
4
SYNC + LUM. SIG. INPUT
"CH3
5
COLOR SIG. INPUT
D.ETAIL (CH.S'N)
6
COLOR SIG. OUTPUT
7
COMPO. SIG. OUTPUT
8
SYNC + LUM. SIG. OUTPUT
9
RF OUTPUT
CH4-
4
I
,
tiLL -
-
10
CHANNEL SELECT SW.
REAR VIEW
RF Modulator Layout and Schematic #251844
11
LIe
COLOR IN
I
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03, 04: 1SS198 OR EQUIVALENT.
02
: 1SS110 OR EQUIVALENT.
01
: 1SS119 OR EQUIVALENT.
TERMINALS
NO.
[
o
,.
1
N.C.
2
AUDIO SIG. INPUT
3
+B (+5V)
4
SYNC + LUM. SIG. INPUT
5
COLOR SIG. INPUT
6
COLOR SIG. OUTPUT
7
COMPO. SIG. OUTPUT
8
SYNC + LUM. SIG. OUTPUT
9
RF OUTPUT
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•
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TOP VIEW
CH¢
• I • CH3
D.ETAIL (CN.SH)
10
CHANNEL SELECT SW.
REAR VIEW
RF Modulator Layout and Schematic #251311
12
Issue 6, 1984 : Computer
Model:
.. commodore
3
PLUS 4
© 1980 COMMODORE BUSINESS MACHINES INC.
Troubleshooting
Aides
NOTE: Visual inspection is critical in this unit!
The upright position of many of the components used on the
board can create problems. It is possible for them to be
shorted to the shield or to each other. Make sure they are
evenly spaced and do not contact the shield.
Areas of the PCB particularly vulnerable to this
problem are:
Bottom right corner - caps
Bottom center - Jl-J6
Bottom left - Q3 shorted to FB57
Top left - ferrite beads
Center - Twisted caps (just outside of RF can)
•
1) NO VIDEO - Absolutely no video on screen
A) Check for 5 volts
O.K.
If not: 1) Check fuse
2) Check for twisted or bent caps
+
( 5 V. short to ground)
3) Check Ll
B) Check for oscillation at pin 14 of Ul
O.K.
If not: 1) Check for good connection at
pin 14 of Ul
+
2) Check for good connection at
Rl thru R7
C) Check for LUM signal at pin 23 of Ul, at pin 4 of
the modulator, at pin 8 of the modulator, at FB3
and at pinl of CN7
O.K.
If not: 1) Check for LUM signal shorted
to ground
+
2) Check for open traces
3) Check modulator
D) Check for reset
O.K.
+
E) Check
Signal
AEC
AEC
CAS
CSI
CSl
CSO
CSO
for control
I.C.
Ul
U2
Ul
Ul
U20
Ul
U20
Pin
35
4
11
6
15
5
1
signals:
Signal
R/W
0
MUX
IRQ
RDY
BA
RAS
I.C.
Ul
Ul
Ul
Ul
U2
Ul
Ul
Pin
7
12
9
8
2
34
10
PLUS 4 Troubleshooting
Page 2
2) BAD VIDEO - Scrolling lines on screen - Random
blocks on screen - Blurred display
A) Check JI-J6
O.K.
•
B) Check
O.K.
for shorts
reset for correct
to ground
or each other
operation
•
C) Check Ul for proper operation
O.K.
If not: 1) Check socket for good solder
•
2) Check for bad Ul
D) Check U2 for proper operation
O.K.
If not: 1) Check socket
+
2) Check for bad U2
E) Check RAM data lines for correct amplitude
O.K.
If not: 1) Check for hot surface of RAM
•
2) Jump out RAM to verify
F) Check multiplexers U9, UIO - signals at RP3
and RP4 should be similar in frequency and
amplitude
O.K.
If not: 1) Suspect U9 or U10
+
G) Check ROM for chip select signal at p.in 22 of
U23 and U24
O.K.
If not: 1) Check for signal generation
•
at U20
H) Check that all ROM addresses are present and
correct amplitude
O.K.
If not: 1) Trace problem address AO-A15
+
I) Check
good
3) NO POWER
A) Verify
U19, U23, U24 by replacement
voltage
+5
1)
2)
3)
with known
and +9 volts
Check for shorts to ground
Check switch
Check power supply
4) BAD BASIC - Random characters on screen - Random
colors - Power-up message is missing
A) Check Basic ROM U23
B) Check B thru I above (Bad Video)
Page 3
PLUS 4 Troubleshooting
5) NO COLOR
or BAD COLOR
A) Check Ul pin 14 for 14.31818 MHz with
frequency counter
O.K.
If no t : 1) Check solder joints of CTI
and adjust for correct frequency
..
2) Check crystal, Ql and Q2
3) Check clock circuit for
opens or shorts
B) Check Ul pin 13 for Color Out signal.
1) Swap Ul w/known good
O.K.
If not:
•
C) Check
O.K.
modulator Ml pin 5 for Color In signal
and pin 6 for Color Out signal
If not:
1) Check Ml operation
•
D) Check FB4 and CN7 pin 6 to see if color
is present.
1) Check for shorts
6) NO SOUND
signal
or BAD SOUND
A) Check Ul pin 33 for SND signal
O.K.
If not:
1) Check socket for open circuit
•
2) Swap Ul w/known good
B) Check audio circuit for short to ground or loss of
signal.
O.K.
If not:
1) Check Q3 - Be sure emitter and base
are not shorted to 5 v.
•
C) Check modulator Ml pin 2 for SND signal
1) Adjust I.F. can (top right of
modulator) for clean, loud volume
2) Ml pin 2 to ground should read
approximately
480 ohms
3) Check Ml for component failure
7) SERIAL
FAILURES
A) Check
B) Check
FB23-26 for shorts
U7, U2 and CN2
to shield
or each other
Page 4
PLUS 4 Troubleshooting
8) KEYBOARD
FAILURES
A) Check
O.K.
pins on ribbon cable
for good connection
•
for shorts - CN5, CN6, FB's, Diodes
•
chip select
B) Check
O.K.
C) Check
O.K.
•
D) Check
O.K.
•
to U27 and the I.C. U27
Ul for proper operation
If not: 1) Check socket
2) Check for bad Ul
9) FAILURES IN SOFTWARE MODE - All units should be checked for
proper operation, when any repairs are necessary.
To Check: 1) Press 'Fl' on keyboard
2) Press 'Return' to enter Word Processing mode
3) Press 'Commodore' key and 'c' key at the same
•
tIme
4) Type ltc' and press 'Return' to enter
Spreadsheet
5) Press 'Commodore' key and 'C' key again
6) Type 'tw' to return to Word Processing mode
Watch
for video or loading
A) Check
O.K •
•
B) Check
jumpers
at JI-J6
Ul, U2, U25, U26
problems,
then:
for correct
connection
Issue 7, 1984
Model:
••
computer
.,. commodore
4
C16, PLUS 4
© 1980 COMMODORE BUSINESS MACHINES INC.
LINE DEFINITIONS
AO to A15
AEC
ATN
BA
BRESET
Cl HIGH, Cl LOW
C2 HIGH, C2 LOW
CAS
CLK IN
COLOR
COMP
CE
CS
CSO
CSl
CST MTR
CST RD
CST SENSE
CST WRT
CTS
DBO to DB7
DCD
DRAM
DRAM ADD
DSR
DTR
EXT AUDIO
GATE IN
IRQ
KO to K7
KERN
LUM
MUX
PO to P7
RAS
RESET
RxC
RxD
R/W
RTS
SND
TED
TxD
'f 0
f2
Address Bit 0 to 15
Address Enable Control
Attention
Bus Available
Buffered System Reset
External Cartridge Chip Select
II
Dynamic RAM Column Address Strobe
Master Clock (Single Phase, 14.31818 MHz)
Chroma Output
Composite Chroma and Luma
Chip Enable
Chip Select
Low ROM Chip Select
High ROM Chip Select
Cassette Motor Control
Cassette Read
Cassette Sensor
Cassette Write
Clear To Send
Data Bit 0 to 7
Data Carrier Detect
Dynamic RAM
Dynamic RAM Address
Data Set Ready
Data Terminal Ready
External Audio Input
R/W GATE
Interupt Request
Keyboard Latch 0 to 7
Kernal ROM Control Line
Composite Sync and Luminence
Address Multiplex Control
Port Bit 0 to 7
Dynamic RAM Row Address Strobe
System Reset
Receive Clock
Receive Data
Read/Write Line
Request To Send
Sound Line
Text Display
Transmit Data
System Clock (Varies between 1 and 2 MHz)
Artificial,2,
Address Valid Rising Edge,
Data Valid Falling Edge
Issue 6, 1985
Model:
: Computer
C-64,
SCHEMATICS
C-16,
1
I[ commodore
Plus 4
FOR C-64,
©
C-16, PLUS 4
1980 COMMODORE BUSINESS MACHINES INC.
These computers have been affected by an Engineering
Change Order that adds 4 diodes to the serial port. These
protection
diodes are not required as field upgrades. They
are 1N914s and were added as a circuit improvement.
The Schematic and PCB Layout for the C-64 in the
Service Manual (Pages 28 and 32) include these diodes.
However, the C-16 and Plus 4 Service Manuals were completed
before the changes were made. The Schematic corrections
are
shown below:
., ~.
I
lie:
4 -+sv
m
~
"J
~/N
f.
4
7
lJlOI
I ,.,
'
t\J
~
II
11
CST WitT
< I
~'~
~
I
l'-.A/
.j
II(
~
Q..
'->
It,.,
U't'
• •
C-16 SCHEMATIC
2.
F822
C.
I
SERIAL BUS
CD PIN
FEMALE
DIN
--
I
FB23
6
5
DATA
ROY
,
N
7'10(0
FB24
-U:;-9
5
3rD
~
0,12
4
elK
,FB25 ,
/5
ro
<:9
~
3
ATN
FB'ZG,
+5V
R23
R24
R2S
114><,3
y
II
28
C5T MTR
27
~
.b'
".... ".,.
9,~lQ()
~,y
./
II/!
/'
C5T WRT
A.
3 , J,....., ........
I
N.C-
1
t •.
CRiP+
C5T RD 2(;,
-': ...
fI}
(J, :.".:0
~::e
-::.::""'
j
t;;""
PLUS 4 SCHEMATIC
<:5
U2.