Fuse for Jolida SJ 502 A

I have recently purchased an older SJ 502A that did not work as a rehabilitation project. The fuse is burnt out on the amp and I need to replace it but I'm not sure if the one that was in the unit is the proper fuse. It had a 6.3A 250 Volt short fuse in it but when I replaced this one with a matching fuse there was a LOT of buzzing in the speakers (with volume all the way down) that can be diminshed somewhat with bias adjustment. Two questions for the Agon experts: What is the correct fuse for this amplifier? Can the buzzing be eliminated with out electronic surgery?

Any information you can provide would be greatly appreciated.

BTW: I have asked this question of the people at Jolida and they referred me to the internet to search for parts and answers.
It seems like it doesn't recognize the presence of input. You may check condition of input tube and if it's normal than I'd suggest looking arround elements on the DC and signal path for both input and splitting tubes.

It's more likely an electronic surgery problem since if tube going bad in these amps it may take some other circuit elements with it.

The fuse you're using the most tube amps use so it shouldn't be an issue.
The fuse you describe doesnt sound right.
I had a 502A and had to replace the fuse.The fuse # you mention are different and it was a slow blow.
Jolida told you to get help off the internet? If I were you,I would call them back and ask again for help.Even though you bought it used,they should still support you and not blow you off.
Tell them about the awesome customer service of other companies mentioned on audio sites on the internet and if they would like the quality of their customer service discussed on the internet.