According to my notes, you have a problem with power amp. Couple questions,
A) How old is this unit? May still be in warrenty.
B) What do you have the power level set at? I like to run mine at at 85%.
C) Is this a heavyly used repeater?
D) Using the software, look at the internal temp. If to high, it will clamp the PA.
Here is a code list
List of error codes for the IC-FR3000/FR4000 series.
Date of issued: 2004/06/01
Error Codes Description
ALT1 Warning Code of the abnormalities in temperature of the final stage of the transmitting circuits. (I.e. It displays when the temperature of the final stage of the transmitting circuits increases due to condition of the antenna.) PA Unit Temp. Check the temperature settings in the software. Cause - PA over heating or PA is going bad.
ALT2 Warning Code of the abnormalities in temperature with the power supply. Regulator Unit Temp
ALT3 Warning Code of the PLL unlock in transmit.
ALT4 Warning Code of the PLL unlock in reception.
01HALT34 Out Of Freq Range This means ALT3 and ALT4
