Modifications for the Kenwood
19-07-1998 Solution 9k6
This is what I found a service
technical report from Kenwood acc. TM255 and TM455 9600bps Date November 8,
SUBJECT: Countermessure against modulation during packet 9600bps
A trouble modulation malfunction during packet
9600bps operation was found in the manufacturing process even trough there in
input in the DATA terminal.
Pay heed to this trouble in replacing the analog
This trouble is cuased by variation in the analog
Even if the 9600bps SW Tr.(Q20:DTA124EK) has been turned ON, the
analog switch IC remains unstable.
We decided to
raise the analog switch IC13 voltage while the 9600bps SW TR. (Q20:DTA124EK) is
in action by changing the chip resistor R117 in the TX-RX-unit of TM455A/E and
R117=10K to be replaced with 3K3
you have problems with those two say to your dealer to ask for SERVICE TECHNICAL
REPORT No. B510-94-081E page 1/2 and page 2/2
73's DE PAT
06-08-1999 Mods for
the Kenwood TM-255E
Adjust LOW power setting
way to adjust low power is to regulate VR401. This trimmer can be found under
the speaker (regulates power between 2 and 30 watts).
To regulate the power of the HI position is to adjust
VR601. You can find this trimmer on the back left side (remove top and locate
the alu cover).
Please be carefully when you dismount and locate the
Adjust TX-Power/SWR ratio
At the same place you
can find VR603 and that is the SWR protection control. Be carefull when
adjusting this trimmer, because it protects your transceiver against bad SWR,
but can be usefull when power drops to much on relative good
To adjust the AGC time constant of the
transceiver locate VR402 that can be found on the left side at the center when
removing the top.
Please be carefully with these
adjustments! All modifications you make is totaly at your own risk.
have any other mods for this good transceiver then please contact
73's De Guy ON1DHT @ ON0BWP.#BTN.BEL.EU
QTH: Aalst, Belgium,