March 18, 1990
Subject:       Kenwood TM-631 failure
Product:       Kenwood TM-631A 144/220MHz FM Dual Bander Radio
           other related products;
               Kenwood TM-731A 144/440MHz FM Dual Bander
Serial Number: 0100055
Options:       CTCSS Unit TSU-6
 installed     Autocode ID'er
               Cross Band remote modification
Antenna:       Larson 5/8 wave - VSWR 1:1.3 (146.000MHz)
Purchase date: 1st December, 1989 from HRO, Anaheim, CA.

Problem:       No 144 MHz receive, No 144MHz transmit but RF meter 
               indicates full power out. 220MHz worked perfectly.
Problem date:  14th March, 1990  the 101st day after warranty
               (Kenwood will not honor repair claim)

Casualty:      144MHz Final Unit (X45-3350-10 A/3), 
                C17 .001 chip capacitor SMT -                 short
                  location - on the bottom of PCB
                 PCB traces burned off and PCB charred
                 Chassis discolored by burned component
                 R11 120 ohm chip resistor SMT -        burned open
                  location - on the top of PCB
               144MHz TX-RX Unit (X57-3400-12),
                 Q1 1st RF Amp chip type transistor SMT -   shorted
                  location - on bottom of PCB
               144MHz TX-RX Unit (X57-3400-12),
                 Q12 transmit switch, chip transistor SMT -    open
                  location - on bottom of PCB

Other issues:  1. RF power meter does NOT indicate RF power out. 
               The power meter is merely a PTT & high/low power 
               select indicator. Service manual is in error.
               2. Chasis casting ripples under PA brick and minimal
               heat sink transfer compound. I lapped the chasis 
               casting, re-applied gernerious heat sink compound,
               and torgued teh PA mounting screws to chasis.
               3. Numeroius suspect solder joints observed on RF 
               PA/TR switching PCB and associated connecting wires.

I've CONFIRMED this failure on three radios and have received 
over 50 packet messages claiming the same failure type occurance 
in the past year, Kenwood USA will not confirm or deny this 
failure mode.
                                               73,
                                               Kuby, N6JSX /9