Tube/valve amp fuses 101

Concretebadger · Post by **Concretebadger** » Fri Apr 04, 2014 11:38 am

Last night my DRRI crapped out on me with no sound and no indicator light. My first port of call, before checking for bad tubes, is to replace the fuse and work it out from there.

I'm guessing the correct type (F1AL 250V, according to what's stamped on the fuse body) is easy to find on places like Amazon (LANK to a pack of ten) but I've seen 'quick blow' and 'slow blow' bandied around.

What's the difference between the two types? Or should I just play it safe and replace the fuse with the exact same thing? Yeah, I know, I ought to have some spare fuses stashed away anyway, because this is the sort of unforseen annoyance that I should be prepared for.

timhulio · Post by **timhulio** » Fri Apr 04, 2014 11:49 am

You want a 1 Amp slo blow fuse in an amp. When amplifiers are switched-on there's a spike in current which blows normal fuses.

*** DISCLAIMER - and in light of the dangerous nature of the topic I'd advise anyone else who isn't 100% sure to also make it known - I am NOT an expert in amplifiers! This is only what I was told to use by an amplifier tech with my sf Deluxe Reverb and sf MM Bass amp ***

jculpjr · Post by **jculpjr** » Fri Apr 04, 2014 12:46 pm

I'll vouch for what Badger is saying. I just replaced a fuse in my VOX and it was 1 amp 250 volt slow blow. Here in the states they are available at Radio Shack brick 'n mortar stores. I couldn't wait 5 days for fuses. They are pretty common and should be available at most hardware stores.

Ankhanu · Post by **Ankhanu** » Fri Apr 04, 2014 2:26 pm

Yeah, Sloblo's the way to go. I was able to get a couple pretty quick at The Source (Radio Shack) when one went in my Twin.

Concretebadger · Post by **Concretebadger** » Fri Apr 04, 2014 2:49 pm

Slow blow makes sense now...there's always surges, pops and arcs when you throw the power switch. That may be what toasted this one for all I know. The slo-blo equivalent would be a pack of these then?

Fortunately I don't need the amp for any upcoming gigs but it's still a bummer, especially when there's a realistic possibility of a valve gone bad.

I've had the amp for a couple of years now so ordering a pair of 6V6s and a rectifier would be a good idea in any case.

Concretebadger · Post by **Concretebadger** » Tue Apr 08, 2014 12:59 pm

Quick double-post to say the slo-blo fuses arrived and the amp seems to be working fine now, so thanks for the advice. I don't believe in fuses blowing for no reason, so I've made a mental note of where the rectifier and output valves are, for when I need to swap them out.

The spare fuses are now in a ziploc bag that's gaffer-taped to the inside of the amp. This won't happen again!