PK87.7
      For older models of the PK-87 the clock speed has now to be upgraded.
Remove C 5 (680pF) and discard the it, then desolder C 3 (330pF) and put it
in the position marked C 5. Put the 220pF capacitor in the position marked
C 3 and change the crystal to the 4.9152MHz crystal. On the top side of the
board between U 5 and U 14 (8530A and 7910) a thin track passes under R 12,
cut this track, see Fig 3.

                            \/ Cut this track
                [         O      o[ 4           Top side of board
             28 [o        :   ____[
                [         :  /  _o[ 5
     U 5     27 [o        : /  /  [     U14
     (8530A)    [_________:/   [ o[ 6  (7910)
             26 [o       +-+   [  [
                [        ! !   [ o[ 7
             25 [o       ! !    \_[                     FIG 3
                         R 12

On the underside of the board link pin 24 of U14 (7910) to pin 9 of U 12
(4040). This puts 4.9152 MHz divided by 2 to the modem chip so it remains at
2.4575 MHz while the rest runs at twice the speed.
CONTINUED IN FILE PK87.5