Hello - I am recapping the amplifier in a circa 1982 Proton 300 Table Radio and am unable to find one cap - part 17-2.5SF405M, Electrolytic Bipolar 4uf 25V. The closest I have found are 3.3uf and 4.7uf. I do not know what function the cap is serving and do not know the ramifications of trying to find a work around. Surprised to not be able to find the appropriate part - wondering whether there is a generally accepted swap for some other size/type of capacitor? Please advise in layman terms. Much appreciated. Thank you.