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IC-730 most common service | Radioaficion Ham Radio

IC-730 most common service

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ICOM IC-730 most common service

My 730 has no RX/TX at all. Display is OK.

Resolution

You have an open R1 resistor on reg. unit. Replace R1 resistor (4.7 ohm, 1/2 watt).


 

IC-730-Preamp-My 730's preamp is inoperative or intermittent. The RX is sometimes noisy.

Resolution

Possible causes:
1) Bad preamp RL1 relay on RF unit.
2) Cracked solder on RF unit in preamp section.

To fix:

Replace bad relay RL1 (FBR221D012). Carefully examine the preamp section of the RF unit for bad joints and resolder as needed.


 

IC-730-Poor Sens.-My 730 has intermittent low RX sensitivity. Actuating PTT temporarily restores RX or causes it to drop out again.

Resolution

Probable cause:
Intermittent preamp relay on RF unit, or intermittent T/R relay on filter unit.

To fix:

Replace RL1 relay (FBR221D012) on RF unit. If this doesn't help, replace RL1 relay (SR-202) on filter unit.


 

IC-730-Freq Changing-My 730 jumps frequency unexpectedly when turning the VFO knob. The digital display does not track with this jump. The frequency jump is consistent and happens at the same place every time. Actual operating frequency does not match in some parts of the bands.

Resolution

The LDO is out of alignment. Adjust the R22 trimmer pot on the main unit for best performance.


 

IC-730-Unstable freq Error-My 730 has frequency instability.

Resolution

You have dirty RIT/XIT pot and switches. Clean the dirty RIT/XIT pots and switches with Blue Shower solvent.


 

IC-730-Audio response-My 730 has drastic changes in audio frequency response between USB and LSB; i.e. the USB audio has too much bass while LSB audio has too much treble. The TX frequency response is also poor.

Resolution

There is misadjustment of the BFO or IF shift oscillator. Realign the BFO and IF shift oscillator as per pages 8-4 and 8-5 of the service manual.


 

IC-730-TX Output-My 730 has intermittent TX output.

Resolution

there are cracked solder joints at J3 connector on the RF unit. Resolder these solder joints.


 

IC-730-Poor TX Audio-My 730 has a distorted/raspy-sounding SSB in TX. Carrier power present in SSB modes. Complaints of RFI. Unit tests fine on dummy load.

Resolution

Probable causes:
1.) Inadequate station ground.
2) External power supply used with unit needs additional RF decoupling.

To fix:

Recheck station ground and improve if necessary. If a 3rd party power supply is being used with radio, install additional decoupling capacitors across the output terminals.


 

IC-730-Low Output-My 730 has TX oscillations, or low spurious output.

Resolution

Possible causes:
1) Bad Q5 transistor on RF unit.
2) Bad electrolytic capacitors on PA unit.
3) Band switch is misaligned. 4) Bad drivers or PA transistors.

To fix:

Disconnect J2 connector on the RF unit and see if the problem goes away. If it does, then Q5 transistor is most likely bad (replace it with a 2SC2878B). If disconnecting J3 has no effect, examine the PA unit. Replace C18 and/or C23 capacitors if they appear swollen or overheated. Check alignment of the front and rear band switch wafers. If none of the above are causing the problem, then most likely the drivers or PA final transistors are bad.

If Q5 transistor on the RF unit is a 2SC945, it should be replaced with a 2SC2878B

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