BBC Microcomputer Service Manual Oct 1985 Section 1 BBC Micro ...

R39-100k R47-1k5 R61-1k0
ii) Solder all of the above passive components onto the main PCB.
iii) Insert all of the above integrated circuits into their sockets.
iv) Cut the wire links at link positions S2, S12 and S13. (S12 and S13
should already have been cut on Model B's)
v) Set the following link positions using MOLEX jumpers:-
S18-North
S19-East
S20-North
S21-2 x East/West
S22-North
S32-West
S33-West
vi) On issue 1, 2 or 3 boards only, the following modifications are
requi red:
Remove the capacitor C17 and replace it with a 2. 2nF capacitor. Cut
the PCB track from IC26 pin 6 to IC96 pins 1 and 19 leaving the track
from IC26 pin 6 to IC97 pin 2 intact. Cut the track from IC89 pin 26 to
IC97 pin 4 and link IC26 pin 9 to IC96 pins 1 and 19 and also to IC97
pin 4.
vii) Test using a FIT and, if available, a PET.
4.6 Modification F
Add 8 inch disc interface to Model B
(As Modification D - Add 5 1/4 inch disc interface, but add....)
x) Set the following link positions by cutting the indicated PCB track
and inserting a wire link.
LINK CUT TRACK WIRE LINK.
S4 East (Solder side) West
S10 West (Component side) East
S27 West (Solder side) East
4.7 Partial upgrading
If you want to upgrade a Model. A to enable it to run software intended
for use with a model B, but do not want all the various interfacing
facilities, then it is only really necessary to add the RAM and the
6522 VIA and change link 525. The VIA is needed as some professional
software uses its hardware timers.
If you want to use sideways ROMs then you will need to add the 74LS163
(IC76) and be sure that links S12 and S13 are cut.
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