Modifications for the Kenwood
TM-455
19-07-1998 Solution 9k6
TM255/455
Dear OM's
This is what I found a service
technical report from Kenwood acc. TM255 and TM455 9600bps Date November 8,
1994
SUBJECT: Countermessure against modulation during packet 9600bps
operation.
Phenomenon:
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
switch IC13.
Cause:
This trouble is cuased by variation in the analog
switch IC13.
Even if the 9600bps SW Tr.(Q20:DTA124EK) has been turned ON, the
analog switch IC remains unstable.
Counter messure:
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
of TM255A/E.....etc.
R117=10K to be replaced with 3K3
So if
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
KE6MIQ
23-04-2000 TM-455A/E
Change in pin diode
Author:
Kenwood Communication, inc.
Service Bulletin no. 1058 (6 May 1994)
Symptom:
Some early versions of the TM-566A/E have been discovered
with a bad solder connection at the final module pin diode, D601. If the
impedance of this devices is too low, the power consumption for this devices
goes up. This increased power consumption might cause excessive heating of the
solder connections, and may result in a failure of the connection(s) after long
FM transmission.
Countermeasure:
On the TX/RX unit replace diode D601 with a UM9401,
change R606 to 100 ohm, change C623 to 5 pF, and C624 to 12 pF. After replacing
these parts, readjust the NULL and Protection circuit using the procedure
provided in the service manual.
Parts required:
Qty Description Part No. Circuit Description
1 Pin diode UM9401 D601
1 100 ohm chip resistor RS14DB3A101J R606
1 5 pF chip capacitor CM73F2H050D C623
1 6 pF chip capacitor CM73F2H060D C624
Time required for this modification is 60 minutes or less.