I PRESENT HERE AGAIN THE MODS FOR AMTOR OPERATION
FOR THE ICOM 720A TRANSCEIVER.

ON MY ICOM 720A I DID THE FIRST SET OF MODS (BY G4ICM)
AND NOW MY ICOM 720A WORKS WELL IN AMTOR AND PACKET !

I HOPE THAT THIS INFOS ARE USEFUL FOR SOMEONE!

                              73 DE IK3BVD OP.ENRICO
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MODS FOR THE ICOM 720A:

MAIN BOARD:  CHANGE C40 C42 C43 C54 TO 0.1 MF
CHANGE C69 TO 0.01MF.

I.F. BOARD: C87 MAY BE 33MF, BUT SHOWN AS 0.0047MF, WHICH IS ON
PRINT SIDE.
CHANGE C87 TO 2.2MF, LEAVE 0.0047 ON PRINT SIDE.

R.F. BOARD: REMOVE C169 C127. CHANGE C165 TO 0.47MF.

NOISE BLANKER UPDATE. (CHECK IF DONE)
CHANGE C116 TO 10MF
CHANGE C171 TO 0.01MF

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DELETE C40 AND C43 ON MAIN UNIT

CHANGE C42 AND C43 (10MF AND 2.2MF) TO 1MF.

DISABLE A.F.MUTING- LINK SHORT-C69.

DELETE CAP. CT14 AT PIN 6 OF IC3 ON I.F. UNIT.

REARRANGE THE R9V TO TR Q22 ON I.F. UNIT
SO THAT IT IS CONNECTED TO UNSWITCHED "9VOLTS SUPPLY.

DO A SIMILAR MOD. TO THE "9 VOLT SUPPLY TO THE A.F. UNIT TO OVERCOME
SURGE PULSE.

==============================================================================

MAIN UNIT: DELETE C40,C43
IF UNIT:   DELETE C87 AT PIN 6 OF IC 3
PICK UP AUDIO FROM ACCESSORY SOCKET (600 OHM)

==============================================================================

CONNECTIONS TO ACC. JACK ON THE BACK OF THE TANSCEIVER:

PIN 3 KEYLINE (NOTE THAT 200 MA CURRENT CAPABILITY IS REQUIRED
               SO A DIL RELAY MAY GIVE PROBLEMS)
PIN 4 AF TO CONVERTOR
PIN 9 FSK INPUT TTL LEVEL
PIN 8 GROUND

ON MAIN BOARD:REMOVE C40/42/43/54 AND REPLACE BY 0.1 UF
              REPLACE C69 BY 10 NF
ON RF BOARD  :REMOVE C169 AND 127 AND REPLACE C165 BY 0.68 UF
WHEN DESIRED THE RELAY TO CONTROL  AN EXTERNAL LINEAR AMP
CAN BE DISCONNECTED TO REDUCE THE CLICKING NOISES