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

Edge connector pin number |6|7|8|9|10|11|12|13|14|15|
1C98 pin number |1|3|4|5| 6| 7|10|11|13|14|
Note: On the edge connector, pin 1 is nearest the speaker, thus the
polarising key is pin 3 and pins 4 and 5 are "empty".
Also check that there are no short-circuits between any of the edge
connector pins. Repeat the tests for the other edge connector.
v) Insert ICs 98 and 99, turn the machine on and type:
REPEAT SOUND-1,GET,0,0:UNTIL0
Now press any alphanumeric key and you should hear the voice synthesis
operating. If the pitch is wrong, follow the instructions in vi) below.
If there is no speech, double check the modifications and try again.
vi) The pitch of the speech must be set. From Issue 4 PCBs onwards this
is a simple matter of adjusting VR2 which is situated just west of
IC98. On Issue 1, 2 and 3 PCBs, the resistor R32 (between ICs 98 and
99) may need to be changed to achieve the best result. The method for
setting the pitch is to connect a frequency meter to pin 3 of IC99 and
to adjust VR2 until the meter reads 160 kHz (+ or - 100 Hz), or as
close as is obtainable by changing R32.
vii) Reassemble the machine. Before fitting the ROM socket cover into
the
the case lid, remove the rforated section of the black label above the
ROM sockets. It may be necessary to trim the label to match the case
cutout. For early version cases (without a rib on the underside behind
the keyboard cutout), remove the two small lugs on the ROM socket cover
before fitting.
viii) Test using a FIT and, if available, a PET.
4.4 Modification D
Add 5 1/4 inch Disc Interface to Basic Model B
i) The following parts are required:-
1 off 8271 IC78
2 off 7438 ICs 79,80
1 off 74LS10 IC82
2 off 74LS393 ICs 81,86
2 off CD4013B ICs 83,84
1 off CD4020B IC85
1 off 74LS123 IC87 (Not required if Econet already fitted)
1 off 2764 EPROM (DFS) IC88 (or IC100 if Econet fitted; but not
required if DNFS already fitted)
ii) Insert the ICs listed above into the sockets provided on the main
circuit board.
iii) On issue 1 or 2 circuit boards only, connect the two pads of link
position S8 with a wire link.
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