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From: wa2ise@cbnewsb.cb.att.com (robert.f.casey)
Newsgroups: rec.radio.amateur.misc
Subject: TH25 and 45 automatic power off defeat
Keywords: mod
Message-ID: <1991Dec10.044456.26533@cbfsb.att.com>
Date: 10 Dec 91 04:44:56 GMT
Sender: news@cbfsb.att.com
Organization: AT&T Bell Laboratories
Lines: 57


copied from packet:
 Msg# TSF  Size #Rd  Date  Time From   MsgID        To
 8733 BF   2759   0 08-Dec 0330 KD2EJ  28521_WB2QJA INFO@ALLBBS ()
 Sb: TH-25-45AT AUTO POWER OFF.

SB-939

TH-25/45AT Automatic Power OFF Function                            8-02-88

Some users of the TH-25AT/45AT have expressed a desire to defeat the
automatic power off function.  The following modification will explain how
to do this.  It should be noted that this modification does not effect the
battery saver function.

Required Part:

Diode Kenwood Part #1SS133

1.   Disconnect the battery pack and antenna.
2.   Remove the Volume, Squelch, and Tuning Control knobs by pulling them
straight up from the top panel.
3.   Using a 7mm spanner wrench, remove the nut from the volume control and
the nut from the tuning control.
4.   Remove one screw located by the PTT switch.
5.   ReMOve one screw located by the speaker jack.
6.   Remove two screws from the battery terminal plate.
7.   Carefully pull the front panel up from the transceiver  (do not break
the wires connected between the front panel and the body of the
transceiver.)  Lay the front panel to the side of the transceiver (Keep
track of the F.LOCK cover if it comes off.)
8.   Remove the PTT cover.
9.   Remove one screw from the PTT switch unit.
10.  Gently lift the top panel from the transceiver by pulling it forward
and then up (the "O" ring on the BNC connector will produce some tension.)
11.  Carefully unfold the flex Printed Circuit Board (PCB) to expose IC2.
12.  Using a 45 watt (or less) soldering iron that has an isolated or
grounded tip, add a diode between pins 23 and 58 of IC2.
13.  Carefully assemble the transceiver by reversing step 1-11.  Pull the
BNC connector "O" ring up a little before installing the top panel.
14.  Reset the microprocessor by following the procedure in the instruction
manual (page 16) called CLEARING ALL MEMORY.

This is an optional change that is not covered under warranty.
Time required for this modification is 1 hour or less.

SYSOP NOTES:  Later versions of the TH-25/45AT came with a programmable
defeat for the Auto power off function.  Do not install this modification
if your manual provides a procedure for turning the power off function off!
Step 11 tells you to carefully unfold the flexible pc board.  It is
extremely important that you do not try and bend the board in a direction
that is opposite from its current bend.  To do so will break the board or
the foil traces inside the board!

(c) 121589TKC
=============================================================================
Note: I haven't tried or verified this, proceed at your own risk. WA2ISE