Slow power-up on black face vibro champ

[AldenFarmboy@xxxxxxx]

Hi,
    I have a chance to buy a Fender black face vibro champ amp from my uncle, 
but I'm worried about something. When i turn the amp on, it takes about 10 
seconds before i get any sound out of it with my mic. After that it's o.k. and 
sounds great. Is this normal for an old amp like this ? Would new tubes help ? 
I think it's from 1966. He said he has not plugged it in in about 5 years. Any 
help would be appreciated. Thanks.