Modifications for the Kenwood TH-22



19-07-1998 TH-22E and CLONE

After expanding of TH-22E by cutting the wire, I have gained much wider band and several options. "CLONE" is the one of them.
You can run it by pressing the REV button when turning on the handie. The text "CLONE" will appear on the display and you can start cloning by pressing the PTT.



19-07-1998 TH-22AT Beyond Mars Modification

This Mod is TH-22AT Beyond Mars Modification Dated November 12, 1993 from Kenwood.
  1. Turn off the power.
  2. Remove the batery pack.
  3. Remove the two long screws from the rear or the case.
  4. Remove the two knobs from the top of the unit.
  5. Remove the rubber top panel.
  6. Squeeze the bottom of the front panel togather an GENTLY separate the two case halfs. Use caution so that you do not damage the thin ribbon cable connecting the front panel to the main unit.
  7. Remove diode D208. Located on the circuit board behind the front panel. See ascii artwork below.
  8. Place the diode you just removed (D208) in the location shown for D212 and solder in place. Observe proper polarity. The diode should face the same direction as diode D210 and D211.
  9. Reverse steps 1-6 to reasemble.
  10. Reset the microprocessor. 
    |   
    |
    |  ---  [D206] [D210]
    |  |C|  [D207] [D211]
    |  |N|  [D208] {D212}
    |  |2|  [D209] {D213}
    |  |0|
    |  |3|
    |  ---    ____|-----|
    |        |    |     |
    |        | SP | MIC |
    |        |    |     |
     ----------^-----^--------
This modification requires soldering equipment rated for CMOS type circuits. It also requires familiarity with surface mount soldering techniques.



19-07-1998 Expanding TH-22 to 136-174 MHz

Hello OM's

the only modification I know and have tested with my TH22E is expanding it to 136-174Mhz range and turning into US mode. Unfortunately I don't think it is possible without opening the case. Here's how to do it:
  1. Remove battery pack and reasseble the case. Open the case carefuly as there's special tape-connector connecting both halves.
  2. Find the little cabels on the top-right corner of the silverplate (on the LCD display part).
  3. One of the cabels in marked as "CH". Cutting this will turn your th22e into channel-only TRX (number of channels will correspond to the memory settings). Better don't cut this - you can set the same from the menu.
  4. Next cabel (to the left of that "CH") keeps the range reduction. Cutting this will expand your portable and turn into US-mode.
  5. Close the case, replace screws, etc. and reset your TH22E (by pressing F-key when turning on). 
here comes the schema of this:
+-----------------+
¦           -  -ch¦+¦       This is the half with LCD display.
¦   cut --> ¦  ¦  ¦ ++ PTT  The look from the silverplate side.
¦   this    -  -  ¦ ++
¦   cable         ¦ ¦
¦                 ¦ ¦
¦                 ¦ ¦
¦                 ¦ ¦
¦                 ¦
¦                 ¦
+-----------------+
In US-mode you can also use the CLONE-MODE. Just keep pressed the the REV/SHIFT key when turning on. Press PTT to start cloning to the other TH22E.



19-07-1998 KENWOOD TH-22E xpansion...WARNING

Hi there.
For those of you wondering how to expand the freq. coverage of your TH22E, this is how you do it:
Remove battery and unscrew the two screws holding the front and back of the rig together. Carefully squeeze the sides of the bottom of the rig together so that the back cover comes unclipped from the from and ease forward to clear the LEDs on top (you will need to peel back the rubber top).
Inside, you will see two green wires marked W201 and W202. Cutting W202 will expand the TH22E from 137MHz to 174MHz on receive AND TRANSMIT.

DO NOT CUT W201! as this will cause the rig only to operate on the memory channel setting and THIS CANNOT BE REVERSED (Meaning that your TH22 will have to be returned to the manufacturer).

Replace backplate and battery.

I hope this is of help to some of you. The W202 mod has been tried by the supplier and the set appears to be working very well. There are some diodes nearby which I assume can be altered to give different RX/TX settings. Any suggestions.



23-04-2000 TH-22/42A/E Memory loss improvement
Author: Kenwood Communication, inc.


Service Bulletin no. 1057 (28 March 1994)

Symptom:
Memory loss can occasionally occur if the following procedure is observed:

  1. Program the memory with any desired information.

  2. Allow the battery pack with to drain down over an extended period of time without turning off the transceiver. For example turn the volume control up and squelch off. After approximately 8 hours the battery voltage will drop to approximately 3 - 4 Vdc.

  3. Turn off the POWER SW.

  4. Connect a DC voltage supply or a fully charged battery pack.

  5. Turn on the POWER SW.

  6. Memory will have been lost.

Corrective Action:
Replace microprocessor IC206 with the improved part listed below. This part incorporates an software improvement to correct this symptom.

Parts required: 

Qty   Description              Old part No.   New Part No.   Circuit Description
 1    Microprocessor           HD404629B17TF  HD404629B49TF  IC206

Time required for this modification is 60 minutes or less.