PK232.37

From    : NZ9E @ WB9HMD.IL.USA.NA

ADDING A "HARD RESET" SWITCH TO PK-232

There seem to be a number of modifications for the AEA PK-232 that address 
the problem of TNC "hang-ups", ie., the PK-232 locking-up in the terminal 
program or simply refusing to stay in the program or perhaps getting 
"lost" somewhere in an undefined loop!  It's happened to mine too, and 
it's frustrating, especially when it calls for a hard reset - erasing 
the back-up RAM and starting the initialization from scratch!

Here's an idea you might want to impliment; it won't keep the 232 from
crashing, but it makes the restarting from ground-zero a bit easier if the 
other modifications you've tried haven't completely solved the problem.

Install a MOMENTARY, normally open push-button switch, on a small bracket,
mounted somewhere on the INSIDE of the 232's cabinet, but accessable via 
a hole drilled in the top cover into which you can insert an insulated 
actuating tool (such as a piece of thin plastic dowel rod, etc.).  
I installed mine on a small aluminum "L" bracket attached to one of the 
screws holding down the AEA daughter-board option, on the left inside 
toward the front.  It's accessable through a 3/8" hole drilled in the 
left side of the top cover.

One wire from this new "hard reset" switch goes via a 10 ohm, 1 watt
resistor to the cathode of diode D12 (this is the 5BB line, or 5 volt
battery back-up line, at least it is in my 232, but check the schematic
for yours just to be sure).  The other wire goes directly to chassis 
ground.  If your TNC requires a "hard reset" in the future, you won't 
need to remove the top of the cabinet and search for the right point 
to short to ground or to resort to having to remove the back-up battery 
jumper and waiting until you "think" that the bbRam "might" be erased.  
You simply turn the power switch OFF and push the new "hard reset" 
switch momentarily to erase the bbRAM.  

Be sure that the power switch is OFF because pushing this switch will short 
the 5BB line to ground (through 10 ohms) and you don't want to do that with 
the power on!  It will also effectively short the Lithium back-up battery 
momentarily, but if you don't over do it, it won't cause any great harm, 
just push it for a second or less, no more than that.  Actually, I've seen
some manufacturer's instructions suggest momentarily shorting the back-up 
battery to clear bbRAM, especially if the back-up battery is soldered into
the circuit as it is in my model of the PK-232 (earlier ones may not be 
from what I've been able to gather).

If you don't think it's a good proceedure, then by all means don't make
the modification; it works for me and I pass it on for what it's worth for
those who will use it with the proper care and forethought.

De Dave, NZ9E @ WB9HMD.IL.USA.NOAM.