Recently I found a Sony ICF 7600GR with same issue.... Radio runs full volume.. can't be controlled... Found a SMD package capacitor C252 ,1uf was short.. 1.2Volt was missing on pin number 14 of IC 203
Check these voltages of IC 203 ( CXA1522P)
Pin -15 Voltage is 1.3V
Pin -14 voltage is 1.2V then" No/low Volume".
Pin -14 voltage is below 0.5 then "Full Volume ".
By varying volume control (RV204 , 50K) , Pin number 14 of IC 203 must vary between 0.3V to 1.2V.