Service manual

Link
Fitted
Effect
Default
LK19
Yes
Used in conjunction with LK18
to select the function of pin 2 of
the Floppy disc drive data
connector B (PL11).
Shunt 2-3
P1 DISC CHANGE VP on
820710
P2 Pin 2 of disc drive
connector
P3 MODE SELECT (polarity
depends on LK18)
LK21
Yes
Used to connect pin 34 of floppy
drive connector B (PL11) to the
Shunt 1-2
DISC CHANGE I/P of 82C710
P1 DISC CHANGE VP
on 82C710
P2 Pin 34 of drive
connector
P3 nc
LK22
Yes
Connection for Power and Hard
disc activity LEDs.
None
P1 HID LED (-)
P2 H/D LED (+)
P3 Power LED (-)
P4 Power LED (+)
LK23
Yes
Used in conjunction with LK24 to
select various combinations of
None
DRAM on the main PCB and the
memory upgrade card.
Total DRAM DRAM LK23 LK24
DRAM on PCB on UM
card
1M 1M – nc nc
2M 2M – nc 2-3
4M 4M – nc 1-2
2M 1M 1M nc 2-3
4M 1M 3M 1-2 2-3
4M 2M 2M 1-2 2-3
LK24
Yes
See LK23.
Model-
dependent
1MB machine nc
2MB machine 2-3
4MB machine 1-2
Plugs
Plug
Fitted
Function/Specification
PL1
Yes
Serial Port. (IBM PC-AT Pinout)
9-way D-type plug.
Pin Signal Pin Signal
1 DCD 6 DSR
2 RxD 7 RTS
3 TxD 8 CTS
4 DTR 9 RI
5 0V
PL2
to
Power supply connectors.
PL6
PL2 -5V PL6 +5V
PL3 +12V PL7 +5V
PL4 0V
PL5
Plug
Fitted
Function/Specification
PL8
No
Floppy disc power connector.
P1 +5V
P2
P3
P4 nc
PL9
Yes
IDE hard disc drive data connector. This is a
40 way box-header containing all the signals
required by the drive in AT mode.
Pin Signal Pin Signal
1 RST* 2
3 DATA? 4 DATA8
5 DATA6 6 DATA9
7 DATA5 8 DATA10
9 DATA4 10 DATA11
11 DATA3 12 DATAl2
13 DATA2 14 DATA13
15 DATA1 16 DATA14
17 DATA° 18 DATA15
19 20 nc
21 nc 22
23 IOW* 24
25 IOR* 26
27 IORDY* 28 nc
29 nc 30
31 IRO 32 IO16*
33 LA[3}
35 LA[2] 34 PDIAG*
36 LA[4]
37 CSO 38 CS1*
39 SLV/ACT 40
PL10
Yes
Floppy Disc Drive Data Connector A. This is a
34-way Box Header containing all the signals
required by the internal floppy disc drive(s).
Pin Signal Pin Signal
2 MODE SELECT 20 STEP*
4 nc 22 WRITE DATA*
6 nc 24 WRITE GATE*
8 INDEX* 26 TRACK0*
10 DRIVE SELECT 0* 28 WRITE PROTECT*
12 DRIVE SELECT 1* 30 READ DATA*
14 nc 32 SIDE1*
16 MOTORON* 34 DISC CHANGE
18 DIRIN*
* All signals are active low.
3,13,15,17,19,21,23,25,2729,31,33 all
5,7,9,11.
PL11
Yes
Floppy Disc Drive Data Connector B. This is a
34-way Box Header containing all the signals
required by a variety of internal/extemal
drives.
Pin Signal Pin Signal
2 See Note 20 STEP*
4 nc 22 WRITE DATA*
6 nc 24 WRITE GATE*
8 INDEX* 26 TRACK 0*
10 DRIVE SELECT 2* 28 WRITE PROTECT*
12 DRIVE SELECT 3* 30 READ DATA*
14 nc 32 SIDE1*
16 MOTORON* 34 See Note
18 DIRIN*
* All signals are active low.
3,13,15,17,19,21,23,25,27,29,31,33 all
5,7,9,11.
Note: Pins 2 and 34 have several functions,
depending on the positions of LK19, 18 & 21.
F-2 Issue 1, November 1991 Appendix F - Main PCB links, plugs & sockets