Bulletin:  SA0140

Subject:  PK-80 Version 1.1.5 Upgrade

PK-80 Modifications to run TAPR Software Updates Versions 1.1.5 and above
-------------------------------------------------------------------------

OPEN UNIT
---------

1.  Remove front-panel screws.
2.  Remove front panel.
3.  Unscrew fastener from regulator at right-hand side of front
    of board.  Remove fastener.
4.  Carefully slide board out of case.

MODIFICATIONS
-------------

Increase Memory from 16K to 32K
-------------------------------

1.  Remove U24 and U25 (Type 6264 8K RAMs)
2.  Cut trace between center and top positions of JMP12.
3.  Add wire connecting the center and bottom positions of JMP12.
4.  Install one Type 43256 (or equivalent) 32K RAM IC in U25.

Modify PUSH-TO-TALK failsafe timer
----------------------------------

1.  Replace C31 with a 47 uF radial lead electrolytic cap @ 15 WVDC.

Set CPU Clock Speed to 4.9 MHz
------------------------------

1.  Cut trace between center and right positions of JMP2.
2.  Add wire connecting the center and left positions of JMP2.

Wire DCD-B to RS232 pin 23
---------------------------

1.  Connect one end of a wire to pin 23 of the RS232 connector.
2.  Connect the other end of the wire to pins 1-2-3 of JMP9 (already
    hooked together on the circuit board)

Replace U3 Op-Amp
-----------------

1.  Replace the LM324 at U3 with either a TL074 or TL084.

END MODIFICATIONS
-----------------

NOTE:  For test purposes, place a good heat sink on the regulator
       chip.  DO NOT operate the PK-80 for more than 30 seconds
       unless the regulator chip has some form of dissipator
       attached!

Reinstall board in case and attach regulator fastener, front panel
and front-panel screws.