Hardware Hacking

Kantronics KPC-3 512k upgrade.
It is possible to expand the KPC-3 memory quite easily with a 128K chip.
Simply plug in the chip and you can get five nodes and a 101000 byte
mailbox. According to the the Kantronics KPC-3 manual, the unit is
expandable to 512K. Unfortunately, no 512K static RAM is currently being
manufactured at prices easily affordable.

By simply using the two extra address lines Kantronics has built into the
KPC-3 along with a few 128K chips and a decoder it is possible to build
512K into the TNC giving five nodes and a huge 491000 byte mailbox!
Kantronics has made available two extra address lines which will be used by
the new expanded RAM. These are used, along with a 74HC139 decoder IC and
four 128K static RAMs to build all 512K into the TNC. Using this
combination will allow five nodes, and a huge 491000 byte mailbox! I used
four KM681000ALP-8 128K static RAMs. If you use a different type, plug in
a single RAM IC to verify it will work.

When inactive, the data lines of the memory ICs are in a high impedance
state. They are neither logic 1 nor logic 0. Address lines are high
impedance inputs. All remaining pins are either for power or left unused.
Except for the individual chip enable lines, all lines may be bridged.
Only when selected will the data lines be active for reading or writing
information.

The 74HC139 is a 2 to 4 line decoder. I am using the original enable line
of U9 at pin 22 to control its output. The extra two address lines select
which of the four output lines will be active when the memory is addressed.
The 74HC139 will drive one of the four memory ICs.

Begin by placing all four memory ICs in a stack. Solder all common pins of
the four ICs except pin 22. Use needle nose pliers to bend each pin 22 at
right angles to its existing position so the four pins stick out to the
side of the stack. The socket for U9 must be removed to allow the cover to
fit when the four ICs are installed. Carefully desolder it and clean all
the pin holes. Solder the four ICs into the space used by U9, observing
the correct position.

Place the 74HC139 on the side of the memory stack with the pins sticking
out. I glued it upside down to the top of the microprocessor, U4. Apply
+5V to pins 13, 14, 15, and 16. 5V is available at pin 32 of U9. Connect
pin 8 to ground at pin 16 of U9. Address line A17 connects to pin 2 of the
74HC139. It is available at J6, pad 2. This is the closest pad to U9,
next to Q1. Desolder the pad and place the wire through the board. Do not
change the trace at J6 between the center pad and position 1. Address line
A18 comes from pin 1 of U9. It is available at a hole through the board on
the other side of Q1 from J6. Follow the trace on top of the board from
pin 1 and you will see it. Desolder the hole and put a wire through.
Connect it to pin 3 of the 74HC139. Place a wire from the empty hole for
pin 22 of U9 to pin 1 of the 74HC139. Finally, connect pins 4, 5, 6, and
7 to each of the four pins of the memory stack. Refer to Figure 1 for
details of wiring the 74HC139.

When everything is wired up, put the jumper across J7 and perform a hard
reset. With the terminal set to 1200 baud, the TNC will report 512K
available memory! Remove the jumper and reprogram all the parameters.
Even with CD SOFTWARE and LEDS ON current in my KPC3 is still less than
15mA.

As an extra note, this technique can be used to increase the memory
in the KPC9612 or KAM Plus as well. There will have to be minor changes
made to the connection points to suit the particular TNC, but the overall
method remains the same.

74HC139
=DA=C4=C4=C4=C4=C4=C4=C4=C4=C4=BF
U9, pin 22 pc board connection =C4=C4=C4=C4=C4=C4=C4=C4=B41 =DF 16=C3=C4=
=C4=C4=C2=C4=C4=C4 +5V
=B3 =B3 =B3
=B3 =B3 =B3
J6, pad 2 (A17) =C4=C4=C4=C4=C4=C4=C4=C4=B42 15=C3=C4=
=C4=C4=B4
=B3 =B3 =B3
=B3 =B3 =B3
U9, pin 1 (A18) =C4=C4=C4=C4=C4=C4=C4=C4=B43 14=C3=C4=
=C4=C4=B4
=B3 =B3 =B3
=B3 =B3 =B3
Pin 22 top 128K IC =C4=C4=C4=C4=C4=C4=C4=C4=B44 13=C3=C4=
=C4=C4=D9
=B3 =B3
=B3 =B3
Pin 22 second 128K IC =C4=C4=C4=C4=C4=C4=C4=C4=B45 12=C3=C4 n=
/c
=B3 =B3
=B3 =B3
Pin 22 third 128K IC =C4=C4=C4=C4=C4=C4=C4=C4=B46 11=C3=C4 n=
/c
=B3 =B3
=B3 =B3
Pin 22 bottom 128K IC =C4=C4=C4=C4=C4=C4=C4=C4=B47 10=C3=C4 n=
/c
=B3 =B3
=B3 =B3
=DA=C4=C4=B48 9=C3=C4 n/c
=B3 =C0=C4=C4=C4=C4=C4=C4=C4=C4=C4=D9
=DA=C4=C5=C4=BF

Figure 1. 74HC139 wiring diagram.

Send a message via packet to VO1KS @ VE1BBS.NS.CAN.NA if you have further
questions or comments. Email ar772@chebucto.ns.ca
73 de Warren VO1KS

————————————————————————
| dear sir,
|
| having a a bag full of 128k srams, i decided to do the mod listed in
| kpc3_2.txt, but before i started, i reviewed the mod itself.
|
| Please add the following to kpc3_2.txt:
|
| This mod is only partially correct, and as it is now, will not work.
|
| The standard pinout for a 32-pin DIL package 128kx8 SRAM is indeed
| very similar to that of a 32-pin DIL package 512kx8 SRAM, with the
| following exceptions:
|
| On the 128kx8 parts, pin 1 is unused, and pin 30 is CS2.
|
| On the 512kx8 parts, pin 1 is A18, and pin 30 is A17.
|
| On the 128kx8 parts, if EITHER CS1* is high, or CS2 is low, the chip
| is deselected and put into standby mode. In the original mod as found
| on the mods page, CS2 is still in-circuit, but with the TNC in 512k
| mode, it’s an address line subject to changing state. This mod as it
| exists *CANNOT* work.
|
| To make it work, you follow the instructions as given, *BUT*, you must
| do the following additional procedure:
|
| Bend pin 30 on each 128k SRAM out, just as you do with pin 22 [CS1*],
| tie all four pin 30’s together to pin 32 [Vcc]. Obtain A17 from the
| pad for pin 30 and run that over as the A17 input to the decoder.
|
| This will prevent the chip from being put into standby mode when
| attempting to address a substantial portion of the upgraded memory, as
| will happen if the original mod is applied.
|
| Notes:
|
| KM681000B [or any standard pinout 128kx8 32-pin DIL package SRAM]:
| ———————————————————————
| CS1* CS2 OE* WE* I/O Mode Power
| ———————————————————————
| H X X X Hi-Z Deselected Standby
| X L X X Hi-Z Deselected Standby
| L H H H Hi-Z Output Disabled Active
| L H L H Dout Read Active
| L H X L Din Write Active
|
| H = High
| L = Low
| X = Don’t care, one of High or Low
|
| CS1* = pin 22
| CS2 = pin 30
| OE* = pin 24
| WE* = pin 29
|
| Disclaimer:
|
| If you fry your tnc, srams, or fingers, don’t blame me. I have
| personally tested this myself, and found it to work, but I cannot
| vouch for you.
|
| Always verify the technical accuracy of any mod to any piece of
| equipment before you apply the mod. This simple principle has been
| known to reduce the numbers of people performing hari-kari because
| they are too trusting.
|
| jim
| –
| All opinions expressed are mine, if you | “I will not be pushed, stamped,
| think otherwise, then go jump into turbid | briefed, debriefed, indexed, or
| radioactive waters and yell WAHOO !!! | numbered!” - #1, “The Prisoner”
| ——————————————————————————
| kc5vdj@swbell.net KC5VDJ - HF to 23cm KC5VDJ@NW0I.#NEKS.KS.USA.NOAM
| HF/VHF: IC-706MkII VHF/UHF/SHF: IC-T81A KPC3+ & PK-232MBX Grid: EM28px
| ——————————————————————————
| ET has one helluva sense of humor, always anal-probing right-wing schizos!
|

KPC-3 battery backup and reset

Along with upgrading my KPC-3 mailbox and node to 512k, I have added two
other features. One is a battery backup and the other is an external
microprocessor reset. Both of these are very useful for using the TNC
at a remote site.

Normally the TNC is powered via the DB25 connector from the same 12 volt
power supply as the VHF radio. Instead of simply putting jumpers at
J8 and J9 as described on page 96 of the manual, I have placed a single
1N914 diode from J8 pin 2 to J9 pin 1. The cathode connects to J8 pin 2.
The 9V battery is installed as well. It has another 1N914 diode in its
positive lead, sealed with heat shrink tubing. The cathode side connects
to the BATT+ terminal on the PC board. The DC power connector is NOT used.
In this configuration the 12V supply powers the TNC under normal use. If
power fails, the internal 9V battery will take over. The diodes prevent
current from the DB25 power input from charging the 9V battery as well as
preventing a heavy current drain from the 9V battery to the VHF rig when
power is lost. Of course the station will be off the air, but the 9V
battery will ensure the TNC clock continues to run and remains accurate.

The second mod is even easier. A single wire will allow an external
microprocessor reset to the KPC-3. Instead of using the hard reset line,
as described in the manual, I decided to use a microprocessor reset. A
hard reset will return all paramaters to default values, wipe all memory
contents, and you will have to go to the site to reprogram everything. The
microprocessor reset will act as if the power is shut off and back on. No
memory contents or parameter settings are destroyed or changed. However all
connections will be lost. By placing a ground at the junction of R35 and
R49 the microprocessor is reset. R35 and R49 are to the side of the power
switch near the front of the circuit board. Look at page 125 of the manual
for placement. R49 isn’t actually installed in the board, and a
convenient hole is provided. Place a wire from the empty hole to pin 2 of
J9. You will then have a reset line on pin 7 of the DB7 connector.

The reset control is provided by a homemade DTMF controller board. The board
also has a control code to disable the PTT circuitry of the transceiver, and
another to enable it again. This is useful in the case of interference.
Finally a second watchdog circuit provides added security. I can provide
more information on this circuit to anyone interested.

Send a message to VO1KS @ VE1BBS.NS.CAN.NA if you have further questions or
comments.

Mods for the original Kantronics KAM. It is for improvements to both the HF
and VHF ports of the TNC.

— Kantronics KAM HF frontend modification update –

I recently received a Kantronics KAM-Plus modem. After comparing the
schematics of the KAM and the KAM-Plus, I came up with this modification
for the KAM to upgrade it to the improved frontend AGC and limiter used in
the KAM-Plus hf modem.

The specs from the manuals for the KAM and the KAM-Plus are as follows;
Audio Input: HF
FM sensitivity 20mVpp (KAM) 2mVpp (KAM+)
AM sensitivity 100mVpp (KAM) 40mVpp (KAM+)
Dynamic range >60dB (KAM) >80dB (KAM+)

With the help of the schematic and the component layout diagram for the
KAM the location of components is simple and the use of a solder sucker
to clear the holes for the double sided PCB will facilitate a clean job.

Components to replace;
OLD NEW
R17 470 100 (All 1/4 watt carbon resistors)
R18 47K 68K
R19 2.2K 10K
R27 15K 2.7K

Remove CR11 and reinstall with polarity reversed
Remove CR5 and discard
Lift the end of R13 that is common with R1.

Insert one end of a .1uF 50V capacitor into the PCB hole vacated by the
end of R13 common to R1; solder in place.
Connect the other end of this cap to the free end of R13.
Install a 100K 1/4W resistor between the free end of R13, the .1UF CAP
and ground. Use the PCB hole vacated by removing CR5 (ground side).
You end up with a tripod of components.

CAUTION: Some PCB holes having double sided traces may need to be
soldered on both sides of the board to ensure a through board solder job.

This completes the update modification for the KAM.
You will notice a better dynamic range for input signals to the KAM
and an improved limiter using the FM/AM front panel switch. I noticed an
improvement in throughput when operating AMTOR/PACTOR. I also noted improved
CW reception using the ‘AM’ position of the FM/AM switch providing perfect
copy on 160M CW signals.

I would appreciate any feedback on this modification or other improvements:
K5HK @ K7BUC.AZ.USA.NA (APLINK) OR mail to my home address.

73, CARL YOUNG, K5HK /MM2
ABOARD SS KAINALU

HOME QTH: 983 LESTER AVE.
RENO, NV 89502

—————————————————

KAM VHF front end improvement 7 April 1995

Original KAM VHF port audio sensitivity 20mVpp, >60dB dynamic range
KPC9612, KPC3 VHF port audio sensitivity 5mV, 70dB dynamic range

The KAM uses the same modem IC as used in both the KPC3 and KPC9612.
By changing some components the KAM VHF performance can be improved to
the same specs as the KPC3 or KPC9612.

To improve the KAM VHF performance;

Remove R4, R8, Q4
Remove and place jumpers in place of C14 and R6
Replace R9 6.8k with 100k
Replace R26 6.8k with 100k
Replace R28 15k with 470k
Replace C6 0.001uF with 0.01uF

K1 position 2 or off, equalization off
K1 position 1, equalization on

This will change the configuration of the original KAM VHF front end
to be similar to the KPC3 and KPC9612. I use a Mocom70 with direct
audio feed from the discriminator. There is no way to simply increase
the volume level to get more audio. There is a great improvement in
the VHF port performance of my KAM since making these changes.

73 de Warren VO1KS

Packet VO1KS @ VE1BBS.NS.CAN

Subject: KAM hf carrier detect mod.

I noticed that the KAM, when connected or trying to connect, will start
to transmit on top of an other signal at times. This will happen when a
received signal appears just before the the KAM wants to transmit.
It is visible by looking at the mark/space display. After a quiet period
a received signal will light up the bargraph display and the KAM will
transmit on top of it.

Looking at the circuit diagram, I noticed a 1 uF capacitor (c 29) in the
carrier detect circuit. It seems to slow down the detect function more
than desired. Changing the capacitor to .1 uF made the carrier detect
work more the way I expect it to. It is easy to get at. Somewhere in the
middle of the board. There is a layout in the manual.
I didn’t ask Kantronics about it. And I didn’t notice any side effects.
I also didn’t try it in any of the other modes.

Comment to ve3iwj @ ve3iwj. 73 Nand.

KAM ‘98 Single-Port Multi-Mode Digital Controller

DB-9 connector
Pin no. Pin name Function
1 TXA Transmit audio (AFSK out)
2 XCD External carrier detect
3 PTT Push-to-talk
4 A/D-3 Analog-to-digital input 3
5 RXA Receive audio (AKSK in)
6 GND Ground
7 EXT-IN External input for Power/Reset
8 CTRLB Control line B
9 KEY CW Key line