ShortScale.org

Gents,

I went to my folks house last weekend and found my old Marshall Lead 20 (1 x 10 @ 8ohms) Solid State Amp, that hasn't worked in quite sometime. One day I flipped the switch to turn it on, and it didn't light up and no signal/noise passed through. I had 2 other amps at the time, so I just switched to a different one and put that one aside.

Now that I have a little bit more technical/electronic knowledge, I am thinking that the fuse just blew (highly possible as I was using this amp to drive my Heil Talk Box). So I opened it up, and sure enough the fuse looks blown. Here's what I don't understand about fuses though:

The fuse I took out of it that was blown, was a T500mA/250v fuse. When I got the manual/schematic for this amp from Marshall it says:

Mains Fuse - 120v. -T500mA. 220/240v. - T500mA

Does that mean.....

A) It had too high of a fuse in there to start with @ 250v vs. 240v?
B) that depending upon what type of power source you are using you might use a 120v/500mA vs a 220/500mA vs a 240/500mA?
C) I should go with a 120v/500mA fuse (for United States, what I usually consider 110v power)?


If anyone could quell my ignorance it would be most appreciated.

Thanks!

The fuse was rated for higher voltage than what the amp's getting, so that isn't the reason it blew. Either a 125V or 250V fuse (the most commonly available ratings in this range) is fine, as long as the amperage rating is at or below what the manufacturer recommends.

With fuses:

-- Don't use a fuse that's rated below the amplifier's recommended fuse voltage. It's fine to use a fuse rated higher than the amplifier's recommended fuse voltage. Meanwhile....

-- Don't use a fuse that's rated higher than the amplifier's recommended current (Amps). It's fine to use a fuse that's rated for lower amperage, but it will likely blow more easily.

Thanks for the quick response! I'll reply back to this thread if I get it working.