Subject: Mods for the Icom 765 HF Transciever 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 1N914 DIODE FROM THE CATHODE OF D63 TO THE ANODE OF D64. 3. DESOLDER AND LIFT W31 FROM PCB AND SOLDER TO JUNCTION 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. ................................................................. MODIFICATION FOR IMPROVED T/R SWITCHING TIME (PREVENTS DAMAGE TO D45, D46, D47, Q15 ON RF BOARD) PARTS NEEDED: 47K 1/8 WATT RESISTOR 150K 1/8 WATT RESISTOR 1SS53 DIODE INSULATION FOR THE RESISTOR LEAD 1. REMOVE BOTTOM COVER. 2. REMOVE SCREWS FROM MAINT UNIT AND LIFT BOARD. 3. REMOVE R10 (39k) AND R11 (39K) NEAR IC-2. 4. INSTALL ONE END OF THE NEW R11 (150K) TO FOIL TRACE WICH CONNECTS TO C13. INSULATE REMAINING LEAD OF R11 AND SOLDER IT TO PIN 3 OF IC-2. 5. INSTALL NEW R10 (47K). 6. SOLDER D159 (1SS53) BETWEEN PINS 3 AND 13 OF IC-2. CATHODE SIDE OF DIODE (STRIPPED END) GOES TO PIN 3. 7. MODIFICATION IS COMPLETE. NO ADJUSTEMENT IS NECESSARY. REINSTALL THE MAIN UNIT AND BOTTOM COVER. ................................................... ----------------------------------------------------------------------------- MODIFICATIONS FOR GENERAL TX Hi Jean, the all band TX mod is simple, just clip diode #D-53, if memory serves me correctly, you can get to it thru the bottom cover, its on the back of the front end, near either the mode pushbuttons or the keypad, can't remember for sure, U do not have to take the front panel apart, It works, I can vouch for that, but be careful!!!! It tx anywhere. 73 Bill ---------------------------------------------------------------------------- ................................................... THESE MODIFICATIONS COME FROM ICOM EXCEPT FOR PBT AND GENERAL TX. THE MODIFICATIONS WERE MADE BY ICOM ON MY RIG EXCEPT THE PBT AND TX. I MADE THE MOD FOR PBT MYSELF AND IT IS GREAT. IF YOU ARE NOT FAMILIAR WITH ELECTRONIC, LIVE THOSE MODIFICATIONS TO A TECHNICIAN. HOPE YOU WILL ENJOY THESE MODS. BEST 73 DE JEAN-F VE2KAD JEAN-F TANGUY tanguy@cam.org OR/OU ve2kad@amsat.org P.O.BOX 931 AX25 VE2KAD@VE2CLJ.#MTL.PQ.CAN.NA RAWDON QUEBEC CANADA J0K 1S0 ::::::::::::::SALUTATIONS DU QUEBEC:::::::::::::::::: /EX