Sounds like the power supply is not doing its job...caps may need change.....I am just guessing of course without actually examining the gear!

各位師兄,我部机在関机(開机就冇事)一剎那喇叭癸出强勁燥音,怕会燒喇叭.有甚麽方法可以改善.我一向係先開前級,後開後級.関机就相反. 請指教謝謝.