RM100 Fuses

[SickPunk]

I know it says to use the Fast Blo 250mA 1/4 amp fuses but will using 1/2 amp work ok too? I saw somewhere on this board that .315 amp fuses were ok to use.

 

[wesarvin]

Check Fry's or online. They're not too expensive to get the right thing.

 

[Julia]

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=071-808

 

[SickPunk]

Does it matter what amp it is?

 

[Julia]

I have a RM100

 

[SickPunk]

I meant amperage in the fuse. The manual says 250mA 1/4 amp.

 

[drewiv]

I meant amperage in the fuse. The manual says 250mA 1/4 amp.

The okay to use 400mA over the 250mA was approved by Bruce Egnater himself. I believe it's safe if he says it is. Although, I've never used the 400mA as I've never blown a fuse of the 250mA variety.

 

[SickPunk]

But what about the amperage of the fuse? I have 250mA 1/2 amp but it says to use 250mA 1/4 amp.

 

[HughJasol]

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=071-808

Thanks for that link, and it's good to have the exact fuses in the amp's specification. But man, the cheapest shipping option is about $10 - for 5 fuses?! I cancelled my checkout once I got to that point.

 

[drewiv]

But what about the amperage of the fuse? I have 250mA 1/2 amp but it says to use 250mA 1/4 amp.

That's a good question. Anyone? I would go with what it requests, but I don't know much. Maybe one of the electro-techy guys can help out here?

 

[warlok]

I have this cut and pasted from somewhere on this site if it helps. I'd stay at the amperage the schematic/Bruce says.
RM100 FUSES?
This is from the RM100 Randall schematics.
17V Rail: 5A SB(2)
B+ Rail: 1.6A SB (2) [corrected]
Mains (120V setting): 5A SB(1)
Filament Supply: 8A (FB SB ???) (2)
Tubes: 250mA FB (4) (From Pete>> ?Bruce Egnater has stated we can use 400ma fuses for the tube fuses?
Bias: 250mA (FB SB ???) (1)
voltage rating is 250V for all the fuses. 5x20mm glass

 

[warlok]

If someone knows if the "filament supply" and "bias" are fast or slow blow, post it so we can have the correct full list.

Edit - here is a post from Bruce last year in reference to the Filament supply.. "Did you install 10 amp slo blow fuses? I assume you have a meter since you "checked" the fuses. Bet you are using something other than 5881/6L6 tubes? Check for ~6.3VAC across the green wires. Then check on the other ends of the fuses for 6.3VAC. If you blew the fuses again, install 15 or 20 amp fuses. The issue is that many power tubes have a much higher "cold" surge current than the 5881s. They can blow those fuses even if there is no problem."

 

[gag halfrunt]

Great info in this thread. Fuses can kill or save a gig, so I like getting this kind of info from the horse's mouth, so to speak.

Or at least second-hand from said horse's mouth

 

[wyd-open]

But what about the amperage of the fuse? I have 250mA 1/2 amp but it says to use 250mA 1/4 amp.

That's a good question. Anyone? I would go with what it requests, but I don't know much. Maybe one of the electro-techy guys can help out here?

250 mA is a milliamp rating. There is 1000 mA per amp. Therefore 250mA = 1/4 amp, it's just another way to say it.

What you are probably getting confused is the Voltage rating of the fuse which is commonly 250v.

If the man that designed the system says it's ok to use the higher rated 400mA fuse (just under 1/2 amp) then I would definitely assume it is safe. i don't know if I would push my luck with the full half amp fuse.