I'm replacing a fuse for the electroluminescent panel in my 1968 Ampeg bass amp. The factory fuse is rated at 0.25A 300V and runs from the transformer to the panel.
The schematic from 1968 was inside the case (so cool!) and says the following for the fuse:
".22/1000 V OR 1/4 AMP FUSE OR 20 k 25w"
It also says "300 VAC" coming from the transformer.
I can't seem to find a matching fuse, but McMaster-Carr has a 0.25A 500V fuse. Is it okay to go higher in voltage?
Also, if you could direct me to a source where I can get the fuse with a matching inline fuse holder (like this: http://asamarx.com/images/productimages/inline_fuse_holder.jpg), please let me know.
Thanks!
Well, the original spec seems to be 0.22A/1000V - I'd think the 0.25A/500V is probably close enough if the 300V fuse has held up for a while. After all, the quote above suggests that an 0.25A fuse should be OK.
Don't sue me if the amp burns down 
.
BoxheadTim wrote:
Well, the original spec seems to be 0.22A/1000V - I'd think the 0.25A/500V is probably close enough if the 300V fuse has held up for a while. After all, the quote above suggests that an 0.25A fuse should be OK.
Don't sue me if the amp burns down .
No need to sue ;)
From what I've read, it's the amps that count, and you can go higher on the voltage without worries. That opens up my fuse selection a little, but I can't find one with an inline holder.
I just realised that you presumably can't find a fuse in the shape of the original, what's so special about that?
Depending on what the shape of the fuse you found is, you might be able to find a suitable fuse holder at some car audio place?
Try parts express.
http://www.parts-express.com/fuse-index.cfm
I've used them for a variety of things, and I find that their prices are good, shipping is reasonable, and they ship quickly. They seem to have a good selection of fuses and fuse holders.
What size is the fuse? Glass tube with a metal cap on each end? 5mm x 20mm?
The factory fuse, best I can tell (since it's in a once translucent sleeve that has now turned opaque), is a glass type with metal end caps, but it has all metal leads permanently attached to it, much like a resistor or LED (http://rocky.digikey.com/weblib/Littelfuse/Web%20Photos/3AG%20FUSE%20315%20SERIES.jpg)
The fuse itself is maybe 1 - 1.5" long.
Should I remove the plastic sleeve to see what's under there?
An inline fuse holder would make it easier to replace this fuse should it pop again in the future.
can you install an inline fuse holder, say, for a car?
sounds a ton like trying to find the proper rated fuses for the power supply board on my pinball machine. just for kicks i would check out an old pinball parts supplier.
Yeah, I suspect that this:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=070-612
along with this:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=071-804
would do the trick.
They don't seem to have the larger AGC type fuse in anything lower than 500ma, and they don't carry an inline fuseholder for the little GMA fuses. You could improvise and use the panel mount holder inline, or try to find an inline holder for the little GMA fuse, or even solder leads onto the 250ma fuse, but like you say, the holder would make it easier to replace in the future.
On a somewhat related note, the fuse may not be the total extent of the problem. I am reminded of trying to fix an old Peavey amp for my neighbor, and it turned out to be more Berkeleyed than I thought. Old electronics, particularly electrolytic capacitors, go bad with the passage of eons. Be happy if the fuse fixes it, but be prepared for it to blow immediately.
Good luck!
In reply to 1988RedT2:
I jumped over the fuse quickly with a wire and the panel lit right up, so I think the fuse should do it. Many thanks for the links!
1988RedT2 wrote:
Yeah, I suspect that this:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=070-612
Any issue with this fuse being 250V instead of the 300V required from the factory? I know it is 300 volts running to the panel.
It should be fine. Volts won't blow the fuse, amps will. They've got to rate it at something, and 300 is just 20% greater than 250.
