PK-88 DCD STATE MACHINE
Re: PK88 Mods.
PK-88 DCD STATE MACHINE
I have available one file on the PK88 which I downloaded from the AEA
Support Forum on CompuServe.
I could leave a message for you on the Forum requesting the exact
information you require, if you like.
Here is the file, please feel free to pass it on:
INSTALLING THE TAPR DCD STATE MACHINE IN THE PK-88
The AEA PK-88 is not among the TNCs for which detailed
installation instructions are given in the State Machine pamphlet.
It isn't that hard to figure out, but maybe these instructions can
help someone else get theirs working faster.
First, electrical connections. As the TAPR instructions
detail, the gray wire should connect to pin 26 of the 7910 modem
chip (IC10); the violet wire connects to pin 25; the brown wire to
pin 2; and the red wire to pin 22.
The x16/x32 clock is a little harder to find. I located it
on pin 13 of the 4020 clock divider chip, IC22. This is an x32
clock, at 38.4KHz. Connect the blue wire here.
I returned the DCD signal from the TAPR board to the CD pins
of JP4. This involves connecting the green wire to the jumper pin
closest to the rear of the PK-88 board, and closest to the power
switch. Don't connect the green wire directly to this point; it'll
be too short to allow you to put the DCD board inside the case.
I lengthened the green wire by splicing the black wire (discarded
from the ribbon cable earlier in the installation) onto the green
wire. You could also connect this signal to pin 14 of the RS-232
connector, J1. By returning the TAPR DCD signal at this point, you
can revert to original PK-88 DCD operation by simply moving the CD
jumper back to its original position. (especially important to me
since I wasn't too sure the rest of this installation was going to
After making this connection, move the black jumper plug
nearest the power switch to the other position, so it's towards the
rear of the PK-88.
Fitting the DCD board inside the PK-88 case isn't easy!
Before doing anything else, cut off the top 1/8" or so of the pins
on the JMP jumper. (make sure you replace the jumper plug in the
1-2 position!) I ended up wedging the DCD board between the heat
sink and the AM7910 chip. To make this work, you have to loosen
the front screw holding the heat sink in place. Be careful (and
don't retighten this screw all the way) since you could probably
crack the PC board.
That should do it. Open your squelch and enjoy!
GW1NGL NA7KR Kevin Roberts Ham Radio
Page last updated on 09/10/2012 by Kevin Roberts NA7KR a colection of Ham Radio and Electronic Information