Fuse problem:cannot understand what i'm missing

Hello fellow Audiogoners.I need your help.
A year ago i replaced a stock fuse on my Krell SACD mk3 (slow blow 500mA 20 mm (small)) with Hi-Fi Tuning fuse.
I threw away that Krell fuse thinking that i can always buy one at Radio Shack.I did some changes in my system and decided to try how Krell would sound with a generic fuse through my system.I went to Radio Shack and bought a 4 pack of Slow Blow fuses (T 500mA 250V).They all burned down one by one as soon as turned the power switch on.Everything is OK when i put back Hi-Fi Tuning fuse with the same specs.The fuses that burned down were slow blow fuses,500mA .I cannot understand why they are failing but a Hi Fi Tuning fuse keeps working without a problem.Are there any other specs that i'm missing?Please,help me solve this dilemma.Thanks a lot!
I don't think you're missing anything. Sounds like "slow" means something different to Radio Shack's supplier than it means to the other suppliers.

If you go to digikey.com or mouser.com (which are leading electronics distributors) you'll be able to find a wide selection of fuses from various makers, and I think the listings for them may provide links to data sheets which would indicate the specific blowing parameters.

-- Al
What Almarg said, X2. Also- Most towns have at least one real electronics supply house, stocking Buss and/or Littelfuse. Check your Yellow Pages under, "Electronic Equipment and Supplies. Radio Crap fuses(like everything else they sell) are junk and will often fail, given no other reason.
Overhang, I buy my fuses from Automation Direct. I am sure that they carry whatever you need. If anything , it's another source.

Are you sure you have the correct fuse? Perhaps the package is mislabeled, are the fuses marked 500mA SB? If it's a SB it should be a coil of wire and not just a straight piece of wire between the 2 ends.

I've bought a lot of fuses at RS over the years and never had a problem. They don't make them so it is highly unlikely that their definition of slow blow is different than others. Something else is going on.
The "T" instead of "SB" probably means "Time Delay".

The delay characteristic may be different from the fuse supplied by Krell.
I went through the same thing with Radio Shack "slow blow" fuses. They are not slow blow. The construction looks like regular fast blow fuses and "fast blow" they do!!

I ended up ordering from Mouser.