IC-756 Pro3 repair

1.Problem : Blank Screen - only PWR light ( LED ) on - NO TX an NO RX

- bad main board - main proccesor short on +5V line

2.Problem : NO TX - Radio is working fine , but no tx

- Bad Drivers and bad PA

After completing the measurements - I found bad driver transistor 2SC1972 and PA - 2SC5125.Orginal PA and Driver transistor is very hard to find so I decided to use replacements. For PA I put matched 2SC2782 from rfparts.com and for driver NTE343 from newark.com ( also matched pair ).

3. Problem : S-meter show 9s

- but antenna was not connected .

After the measurments I found bad voltage stabilizer on PA UNIT

Note !!!!!

New Icom ( ic-756pro3 ) has option in menu to go to special "ADJUST MENU" and there you can make some of calibration - s-meter calibration,power calibration , etc.

Also you can go to "TUNER MODE" - and you have option to calibrate your auto tunner.

More info you can find in service manual or send me a email tarniowy@yahoo.com

PA unit - this is with new Power Transistors 2SC2782 and NTE343

Note !!! If you are replacing transistor in PA unit you must setup bias current. For 2SC2782 - 500mA

This is view for CTRL-A unit ( this is new unit )

Note !!! Icom have two different units.Difference is PCB pattern.The rest is identical ( number of connector,plugs etc.) That means that units are interchangeable.