Over current at switch on

[Crockett]

Greetings from the "meeting place" state, Tennessee.
I recently turned on my newly acquired oscilloscope and it promptly blew its mains fuse.
I removed the fuse and checked the current. Initially the current jumps when the switch is flipped; but it quickly comes down well under the fuse rating amperage. The required fuse is a 0.5A slow blow 100-115 V 50-60Hz. The fuse I found in it was a 0.5 A, but not a slow blow.
My question is should I just replace the fuse with the appropriate slow blow and not worry about it, or should I do that and also look for what and why the unit briefly draws more than the 0.5 A when switched on??
Thanks,
David

Leader LBO-514

[c4757p]

It's charging up its capacitors. Almost everything takes an inrush when you turn it on; that's why they specified a slow fuse in the first place.

[Crockett]

Yes, I just was wondering if the initial charge up was designed to be that much or if through age they have come to draw more. I guess if I just put the correct fuse in it I'll find out.
Thanks. 
David

[w2aew]

Yes, I just was wondering if the initial charge up was designed to be that much or if through age they have come to draw more. I guess if I just put the correct fuse in it I'll find out.
Thanks. 
David

Just as c4757p stated, the manufacturer wouldn't have spec'd a slow-blow if it wasn't required.

[c4757p]

Yes, I just was wondering if the initial charge up was designed to be that much or if through age they have come to draw more. I guess if I just put the correct fuse in it I'll find out.

I recently coupled a 54W transformer through a rectifier to 28mF of capacitance and it takes over 16A inrush when I turn it on. The initial charge up is indeed supposed to be huge.

[Crockett]

Well, I've got new, correct fuse installed now. So, hopefully I won't be coming back to this thread reporting it not working.
Thanks for the comments and any more are, of course, still welcome.
David