Sounds kie kie kie after 15min play HELP!

this system was brought from my dad office in non working condition with cut input wires so just sort it out with tape & fixit then also nothing work while fixing the wire so just lookout on the transformer & have replaced all the 5 fuses with there rating amp & found 2 where not just working while tested on multimeter now everything is working perfectly expect amplifier after 15 min on medium vol.55 (top 79) sounds like kie kie very low treble sound then vol adjust to 45 then sounds perfectly without any problem if i play whole day.... the only problem is when i raise it vol above 65 up & down rapid sounds kie kie continuous until i low down the vol to 50 when the system was brought it was having lot of dust in pcb ckt i just clean all the dust & clear out thing that it will fix but nothing change all same (system condition was like not used from years) i thing there could be a ic fault not sure for that wheather i need to replace or something....& also no surround sound i am getting on the system while turning on the switch from backside or i will get surround sound only when i used cd player or tape like that because in while using AUX no surround (8 to 16 ohms) only left right (4 to 6ohms) i just what to make this sytem alive again when it used to sound like new system just waiting to feel the sound in full vol. HELP ME GUYS!!!

u just post it i will fixit!!!