PK87.5
      If you have not made the modifications needed on the old PK-87 to the
audio output make then now. They are to turn C 24 round so the positive is
to the RADIO connector and if a TL082C is used as the opamp, to put in
series with the audio output from it to the RADIO connector, a 100 ohm
resistor to stop spurious signals appearing on the microphone line.

      The PK-88 EPROM should now be inserted in the socket and the board
should be checked for any defects such as shorts, solder splashes or bent
pins. The board can now be connected up and tested. If
 all is alright it
will enter the auto baud routine and can be started as from cold.
If there are no problems turn the link block on JP 1 so it links the pins,
remove power and reassemble the unit.

      If you have problems with resets due to spikes on the 12 volt line,
such as when you turn on a radio on the same power supply, either put a
high value resistor in series with D 1 or just cut a leg of D 1.

You should now have a PK-88 in false colours.
If you have problems with overheating or unreliable operation I suggest
you replace the Z8400A with a 6 MHz CMOS Z80 processor as the clock is
beyond the rated speed of the Z8400A, the same can be done for the 8530A.
With a CMOS EPROM and both CMOS Z80 and CMOS SCC the current consumption
can be reduced to below 250 milliamps.

     73   ADRIAN,  GM1FML @ GB7MAC