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TM731A.MOD
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1980-01-01
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TM-731 FREQUENCY AND CROSS BAND REPEATER MODIFICATION
=====================================================
The TM-731a will transcive between 136-174 MHz and 400-500 MHz as
well as perform cross band repeter function when the following
modifications are performed.
1.- Remove both the top and bottom cover. Disassemble the front
panel such that the control unit (X53-3250-XX) is accessable.
2.- Remove R121, R123 and R25. While R125 snd R124 must be present.
3.- If the time-out timer function is not desired, remouve R122 as well.
4.- Reassemble the unit and perform a microprocessor reset before
operating the set.
5.- Preserve your license by operating whithin the bands it is
cover for.
BEST 73's
GERALD
TM731A.1
Thanks to the efforts of our local technical wizard, Bob VE3GVD, we now have
the secret to making the new Kenwood TM-731A do the same fancy tricks that its
sister rig the TM-721A did. Here is how it's done:
1) Remove the top and bottom covers, and take out the screws that will allow
the front panel assembly to swing down.
2) With the rigs front facing you and the top side up, locate R 121 and R 125
which are both immediately to the left of the lithium battery.
3) Using a low wattage iron and tweezers, remove R 121 which is about the seven
o'clock position with respect to the battery and reinstall it in the blank
position designated for R 125 which is about the eight-thirty position with
respect to the battery.
4) Now locate R 25 on the back of the circuit board that is attached vertically
to the main chassis. (It's the board behind the front panel when the panel
is folded up) Carefully un-solder and lift off the grounded end.
That completes the mod. Having a service manual, or at least a board layout
will assist you in locating the components. It will be neccessary to do a
reset on the microprocessor as described in the user manual after doing the
mods described.
For those curious as to what does what, removing R 121 enables the repeater
cross-band function, and the adding of R 125/removal of R 25 enables the out-
of-band features.
73, Weazle, VE3EAR @ VE3WZL.ON.CAN.NA
TM731A.2
TM-731A Modification
Mode repeteur et elargissement du TX/RX
(Repeat mode and extension of TX/RX)
1- Enlevez les resistances R121, R123 et R25. Les resistances R124 et R125
doivent etre en place.
(Remove resistors R121, R123, and R25. Resistors R124 and R125 remain)
2- La fonction timer peut etre desactive en retirrant R122.
(Function timer may be disabled by removing R122)
3- Faire un reset du microprosseur avant de l'utiliser
(Reset the microprocessor)
Bonne modification.
73 de Gerald Ve2bcm
(Translation by VE3EUK. Try at your own risk)
73 de Ralph
TM731A.3
Subject: Kenwood TM-731A firmware bug
The Kenwood TM731A dual bander has a firmware bug that breaks the 2m VFO scanner
in certain circumstances, that is, the 2m VFO scanner won't work properly if
certain PL tones are stored into memory 1. So far, all tested 731A's have had
this problem. The highest serial number tested was 72713. To demonstrate the
problem, perform this experiment:
1. If not already done, load search bounds into memories A and B of the 2m
unit. Verify that the VFO scanner works.
2. Change the PL tone for memory 1 to (for example) 91.5:
select memory 1, press F VFO to transfer it to the VFO, then
press F TSEL and select 91.5 Hz PL tone, then store back into
memory 1 by pressing F MR.
3. Set the VFO to a frequency outside the range given in memories A and B,
then start the VFO scanning (by pressing VFO for a few seconds).
4. If your radio has the bug, it will alternate between the frequencies
stored in memories A and B. If you start the scan while the VFO
is within the search range, it will scan up until the top limit
is reached, then begin alternating between the two limit frequencies.
5. To restore 2m VFO scanning, program memory 1 with one of the several PL
tones acceptable ... the default of 88.5 Hz works fine.
6. The 70cm unit does not appear to have this problem.
----
73 de James Dugal, N5KNX @ W5DDL (70504) or jpd@usl.edu.