Service manual

Appendix F - Main PCB links, plugs & sockets
Introduction
This appendix describes the links, plugs and sockets on the
main PCB of the A5000 computer.
Links
Unk
Fitted
Effect
Default
LK1
Yes
Used to select signal options for
pin5 of keyboard socket (SK4).
Shunt 1-2
Sig. option LK1
PC Kbd clock 2-3
KIN data 1-2
LK2
Yes
Used to select the signal source
to pin 6 of the keyboard socket
Shunt 1-2
(SK4).
1-2 inverted Kout from
IOC
2-3 logic 1
LK3
Yes
Internal auxiliary audio
connector providing access to
the following signals:
None
P1 Unfiltered Left
P2 OV
P3 Left Phones
P4 OV
P5 Aux Input
P6 OV
P7 Right Phones
P8 0V
P9 Unfiltered Right
P10 0V
LK4
Yes
Used to select signal options for
pin 1 of keyboard socket (SK4).
Shunt 1-2
Sig. option LK4
PC bidirectional
data 2-3
reset from Kbd 1-2
LK5
Yes
Used to select the source of
Shunt 2-3
"Keyboard In" data for IOC.
1-2 Keyboard in data
from controller (IC6)
2-3 Kin data
from keyboard
LK6
Yes
Genlock connection point:
Shunt 1-2
Shunt 3-4
P1 Internal video P9 VED2*
dock
P2 Clock to VIDC P10 VED3*
P3 SINK P11 SUPREM-
ACY'
P4 OV P12 HI'
P5 nc P13 HSYNC*
P6 nc P14 VS*
P7 VED0* P15 OV
P8 VED1* P16 OV
Link
Fitted
Effect
Default
LK8
Yes
Connection point for the internal
speaker:
None
P1 OV
P2 Signal
LK9
Yes
Test connector used in
conjunction with Acorn
designed test equipment:
None
P1 5V
P2 D[0]
D[0]
P3 LA[21]
P4 TESTAK
P5 RST*
P6 OV
LK10
Yes
Used to select ROM TYPE:
Shunt 1-3
TYPE
Shunt 2-4
Non JEDEC 512K 1-2 3-4
Non JEDEC 1MB ROM 1-2 3-4
Non JEDEC 1MB
EPROMs
JEDEC 1, 2, 4, and 1-3 2-4
8MB ROMs and
EPROMs
LK11
Yes
Used in conjunction with LK14
and LK12 to select ROM SIZE:
Shunt 1-2
SIZE (Bits) LK14 LK11 LK12
1M 2-3 2-3 2-3
2M 1-2 2-3 2-3
4M 1-2 1-2 2-3
8M 1-2 1-2 1-2
LK12
Yes
See LK11.
Shunt 2-3
LK13
No
Used to select the source of
1-2
Parallel port Interrupt for IOEB
1-2 parallel port ACK' signal
2-3 PINTR* from 82C710
LK14
Yes
See LK11.
Shunt 1-2
LK15
Yes
Used to select '5th column' ROM
size (JEDEC only device).
Shunt 1-2
Size (bits) LK15
up to 1M 2-3
2M 1-2
LK17
Yes
Used to select Normal or
None
Alternate pre-compensation
scheme for floppy drive interface
Pre-comp LK17
Normal (125ns @ 500kb/s) 1-2
(125ns @ 250kb/s)
Alt (125 ns @ 500kb/s) None
(250 ns @ 250kb/s)
LK18
Yes
Used to select the polarity of the
Shunt 1-2
Mode select signal routed
to pin 3 of LK19.
Polarity LK18
PC-AT 1-2
PS/2 2-3
Appendix F - Main PCB links, plugs & sockets Issue 1, November 1991 F-1