Fender Frontman 65 - weird noise for 2 sec. then plays ok

[spunko]

Hello friends! This Frontman 65 has this weird noise at power ON for 2 secconds, and then plays ok.
Also the mute circuit is not working. One jack was faulty and I replaced it but you can still hear the amp hising when nothing is plugged in. Mute is not that important for the owner, unless it has to do with the starting weird noise.

I have checked Q20 and Q5 and they are good. I don't know what else to check for that noise.
Maybe someone have encountered this problem before and can give me a hand.

Thanks again for the help :)

[tubeswell]

how old are the filter caps?

[spunko]

It seem they are original so at leat 10 years. I going to buy some caps and try that.
I have a capacitor tester, so I'll test them first, but they are old either way.