PK87.9 ICS say the faster rate is the standard rate, which means you do not need to change the device in the PK-87, U 12. (The non-standard EPROM is issue 30-DEC-88 checksum $15 and needs the slower rate.) (The 4020 is a 14 stage counter as opposed to the 12 stage 4040 and can therefore divide the clock further but both are pin compatible in the pins that are used in the PK-87 and PK-88. If a change is made it will make no difference, except that if a slower rate is needed the 4020 will give the needed clock on pin 2. Once U 12 is relaced with a 74HCT4020, to get the slower clock rate cut the track going to pin 1 of U 12, at the pin and put in a link from the track to pin 2 of the device.) Before starting it might be an idea to note the parameter settings so that any important ones can be re-entered at the end. Disconnect the cables and dismatle the TNC. Remove the link block from JP1 (beside lithium battery) and replace it on one pin only (disconnects battery from RAM). CONTINUED IN FILE NAMED PK87.1 - REQUEST FROM SERVER