Easy first question : Ampeg B15 fuse question

Rover Eric · #1 06-27-2010, 04:16 PM

Hey, all. I have a question about an Ampeg B15N fliptop i picked up recently. It's a late 70's model, with the blue grillcloth, 4 inputs, etc.

Anyways, after opening it up, everything looks good, except there's 2 hanging wires where according to the schematic would be a 6 amp fuse.

So...is this needed? If so, what does the fuse holder look like, since it's not a surface mount one like the 3 amp fuse? What is the point of two fuses in series?

here's the schematic...the missing fuse is the one circled in ballpoint.

http://farm5.static.flickr.com/4135/...587911a1_b.jpg

and here's the pic of where the inside of my amp has 2 hanging wires, presumably where this 6amp fuse would go. It DOES look like someone just hooked up lampwire or something... like they removed the old fuse and just hooked up some wires and didn't attach a fuse.

http://farm5.static.flickr.com/4138/...9f8f9d4a_b.jpg

So, if someone could help me out with some advice on this, that would be super.

-Eric

BassmanPaul · #2 06-27-2010, 04:57 PM

6A is way too high for a B15. There is only one fuse in the amp.

Paul

Rover Eric · #3 06-27-2010, 05:00 PM

weird. So why does the original schematic that's pasted inside the chassis of the amp show 2 fuses in serial? Mistake?

coreyfyfe · #4 06-27-2010, 05:08 PM

That's odd. My schematics only show the 3A fuse, but my amp is a 65 and the schematics book I have is from 71 so it doesn't have your amp (note the date on the schematic looks like 8-24-77 which makes sense since you said 4 inputs).

Rover Eric · #5 06-27-2010, 05:23 PM

what worries me is that it looks like someone tried to figure this out for themselves, circled the fuse in the diagram.... perhaps they were troubleshooting a constant fuse blowing, and assumed this was the problem.

craig.p · #6 06-27-2010, 08:23 PM

First of all, as far as I can tell, the pre-Rev D incarnations didn't have serial fuses.

Second, my SWAG about the 6A fuse is that it was installed as an inaccessible failsafe in case some moron installed a 10A or something (or even foil) into the panel fuseholder to get around persistent fuse-blowing. OR, if the 3A is a slo-blow, maybe the 6A is a fast-blow to stop a sudden dead short quickly and reduce any collateral damage. Again, I'm just guessing.

From a personal-liability perspective, I think you should reinstall that 6A. If "something strange happens" inside the amp and any surrounding property is affected, you want to be able to say your amp was to spec/to print. A one-in-a-million chance, I know, but still...