Guys, this is part of the issue I am asking about in my other thread...

You might consider that the mains power socket that you are using, assuming you are in US domestic residence is generally rated by your city's Electicial Code is 15 amps, do you really  know what you are doing here?

Also the gold label on the back of the chassis also states 8aSB

stereoisomer,

I have the B&K ST202+ Owners manual and it states:

• Main A.C. Fuse    8aSB
• Speaker Fuses    4aR
• Rail Fuse             4aR

Luckily for me I am the original owner of the amplifier so I don't have to worry about someone else previously changing the fuses to something incorrect. Sadly, one of the many benefits of the Internet Age was NOT helping the smaller, local shops. We had a great family chain here in Dallas that lasted decades.

Now, what you mostly see in brick and mortar stores are "Home Theater Studios" who aren't particularly interested in anything you have to say just how much you're willing to shell out $$$ in the hope your Media Room sounds and looks like an XD 3D theater.

Search ebay for 3AG fuses.

Too much chance of a substandard device.
The fuse is the first line of defense for the amp and speakers

Digikey, Grainger, Mouser, McMaster-Carr
Fuse Manufacturers | Littlefuse, Bussmann, Mersen (fusesunlimited.com)

The extra couple of bux for shipping if you can't buy local is cheap insurance. Buy the exact required fuse. If it goes, there is a problem with the amp. Get it fixed.

In more than ½ century in HiFi, I've never replaced a fuse for failure.
Several because a manufacturer scrimped and installed no name crap.

As normb said, if you have a spare, you'll likely never need it.

also, find a few for sale on hifishark, perhaps someone here, write and ask if they have the manual with the spec,

or, original owner, never changed fuse, if they would look and see what fuses they have in there..

1- user manual (Hifiengine has many online) for OEM part value.

2- eBay, Amazon, Zoro, Grainger, lots of sources.

2 major manufacturers of automotive and audio fuses (generally 1x1/4” or 5x25mm although 20mm length are also common) include Buss and Littelfuse.

3- fast or slow-blow are available in glass or ceramic packages.

4- as mentioned previously, power supply fuses are usually of more robust slow-blow, audio/speaker side of the fast-blow variety.

5- for some examples: https://www.littelfuse.com/products/fuses/cartridge-fuses.aspx

6- always have spares. This almost guarantees you’ll never need one.

From the pictures online it looks like a 3AG fuse holder.  The cap unscrews and the fuse is held in a cup on the cap.  The 3AG fuses are 1/4" diameter x 1 1/4" long.  Which are just about the universal glass fuses used.
Usually they manufacture will mark ampere rating by the holders.  If not check the manual. Or
Remove the old fuses and look around the silver ends of the fuse. Usually engraved is 3AG, 250V and some number with an A after it.  This is the amp rating of the fuse.

However!   Power input fuses may be a "slow blow" type to handle turn-on Inrush current. You can tell a slo blo fuse by the extra stuff inside the fuse. The standard fuse just has a wire running across.  Your amplifier may have been supplied with like an 8amp slo blo input fuse. Someone replace it with a standard 8 amp and it blows frequently upon turn-on. If not immediately. So they upped the rating of the fuse. Wrong way to go.

Search ebay for 3AG fuses.

FYI   Also available are Fast Blow fuses. Those fuses have a white ceramic cover instead of glass.



 

Might be worth your while to check the owner's manual to make sure you (or someone else, if you bought used) didn't "accidentally" replace the fuses with the wrong values at some point in the past.  Nothing worse than having your equipment (or your house!) burn up if the fuse doesn't blow when needed. 

Radio Shack

12A @ 120V is an 1800Watt loading, for the majority of domestic amps that would be some failure to blow that.

Cool, good to know, cleeds thanks for the info..

Regards

oldhvymec

Most are in the 3-5 amp range slow blow in some, charging caps and bringing transformers up. Valves may have more protection a second fuse fast blow on the bias circuit.

Yes. Although it’s unusual, there are amplifiers with larger fuses, including the Conrad Johnson Premier 1B, which does have a 15A slo-blo on the 120VAC line.

Most are in the 3-5 amp range slow blow in some, charging caps and bringing transformers up. Valves may have more protection a second fuse fast blow on the bias circuit.

A Valve goes nutty on it's last turn on cycle, POP and hopefully the FB will pop too. .5 to 1 amp or something.. OR turn the bias up to quick when re biasing.. POP!

@yogiboy 

I'm simply replacing the fuses that came stock with the amp. I'm quite certain there are a lot of amplifiers with higher amperage ratings than mine.

You should remove the fuse and bring it with you to make sure that you replace it with the correct one. There are slow-blow and fast-blow type fuses. BTW, I have never seen an amp with such a high value fuse!  

Thanks, guys! I appreciate it. FWIW, both amplifiers came with 15 amp external fuses. The ST-202+ is pretty powerful on its own so I'm just trying to replace like with like.

Lowe's and Home Depot both have a wide assortment of fuses.

stereoisomer

I want/need to buy some 15-20 amp fuses for my B&K amplifiers. These are the kind that fit into the fuse holder on the back and screw in. Once upon a time, these were easy to find. Now, not so much. The fuse has to fit into the screw-in receptical on the amplifier. Any idea where I could get new fuses ...

It's not likely that your amplifiers really need 15A or 20A fuses. You might want to check your owner's manual. In any event, any good electrical supply house should have the fuses they need in stock.