From INTERNET :

MOD FOR IMPROVED MONITOR VOLUME.

FOR RADIOS WITH SERIAL NUMBERS BELOW 2000

1. SET RADIO FOR 8 MHZ IN LSB
2. ADJUST C226 FOR 1 TO 1.2V AT R201.
3. VERIFY THAT IT GOES TO 3V AT 7.9999MHZ
CHANGE R85(10K) ON MAIN UNIT TO 4.7K.
........................................

PASSBAND TUNING MOD.

1. DESSOLDER AND LIFT CATHODE OF D63 FROM PCB.
2. ADD A 1N9UNCTION OF THE
   1N914 CATHODE AND D63 CATHODE.
AFTER MODIFICATION:
IF SHIFT BUTTON OUT = PASS BAND TUNING
IF SHIFT BUTTON IN  = IF SHIFT.
..........................................

MOD TO PREVENT ANT SW UNIT FAILURE.

1. REMOVE TOP COVER
2. LOCATE ANT SW UNIT AT RIGHT REAR OF RADIO (AT ANTENNA JACK).
3. SOLDER A .0047 UF, 500V CERAMIC CAPACITOR TO BACK SIDE OF
   PC BOARD AS SHOWN. (BOARD REMOVAL IS NOT NECESSARY).
4. REINSTALL TOP COVER AND CHECK FOR PROPER TRANSMITTER
   OPERATION. THIS MODIFICATION PREVENTS FAILURE OF R1, R2, D1 AND L1.


-------------------------------------- TOP EDGE OF BOARD

                     /0\
                   /     \                  REAR PANEL OF RADIO---->
   I----0        /         \
 __I__         /             \
 .0047UF     /0_______________0\
 --I--  0                                  /0/
   I       ________________________       / /
   I------0________________________0     / /
                                        / /
                                       /0/


         VIEW: BACK ANT SW UNIT PCB.

..................................................

THE FEEDBACK CIRCUIT THAT CONTROLS THE TUNING MOTORS BECOMES SENSITIVE
AFTER A FEW MONTHS OF AGEING. IT REQUIRES A ONE TIME ADJUSTEMENT TO CORRECT.

1. REMOVE TOP COVER AND LOCATE THE ANTENNA TUNER BOARD.
2. LOCATE R5 AND R10 AND SET THEM TO THE CENTER OF THEIR RANGE.
3. SET RADIO AS FOLLOWS: TUNER ON
                         FREQUENCY 14.100 MHZ
                         MODE RTTY
4. AFTER TRANSMIT IS ENGAGED FOR 30 SECONDS,
5. ADJUST EACH CONTROL (R5 AND R10) SO NEITHER MOTOR TUNES WHILE CHANGING
   FROM SSB TO RTTY AND BACK TO SSB.
-NOTE: R5 (RIGHT) CONTROLS RIGHT MOTOR AND R10 (LEFT) CONTROLS LEFT MOTOR.
6. REPEAT THIS ADJUSTMENT TO VERIFY PROPER OPERATION AND THEN CHECK ON
   ALL OTHER BANDS.
7. REINSTALL TOP COVER AND RETURN TO OPERATION.
.................................................................