Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: JKRamsey1991 on January 14, 2019, 03:58:30 pm

Title: Fuse Value Question
Post by: JKRamsey1991 on January 14, 2019, 03:58:30 pm
So I built a matchless spitfire clone and have a question on the fuse value. I know AC15s and my Dr Z Monza only use a 500ma fuse, the schematic I used for this build calls for a 2amp. Why the increased value and is it necessary? I did just blow a 500ma fuse playing it hard after about an hour. I can’t find anything wrong in the amp and replaced the fuse and it’s operating fine no signs of any issues all voltages look good and it sounds fine. So I’m tbinking if the 2 amp fuse is truly needed that’s my problem.
Title: Re: Fuse Value Question
Post by: jjasilli on January 14, 2019, 04:03:17 pm
AC-15 uses 2A fuse.  See:  http://www.valvewizard.co.uk/fuses.html
Title: Re: Fuse Value Question
Post by: PRR on January 15, 2019, 12:09:08 am
120V land or 240V land?
Title: Re: Fuse Value Question
Post by: bmccowan on January 15, 2019, 08:58:09 am
I built a spitfire clone here in 120V land - it has a 2A - no problems. Comment - amp was too bright for me, I removed the bright cap - much better.
Title: Re: Fuse Value Question
Post by: JKRamsey1991 on January 15, 2019, 03:15:37 pm
120v here. Maybe I just looked at something wrong. I’m going to plug in a 2amp I’ve played it a few hours with the 0.5amp with no issues so I’m pretty certain it’s okay.

I also removed the bright cap on mine!
Title: Re: Fuse Value Question
Post by: turtle441 on January 16, 2019, 01:15:26 pm
Have to look at where you're fusing things as well.  My Spitfire/Lightning combo used a 2A Sloblo on the mains and a 500ma fastblo on the HV secondary. 
Title: Re: Fuse Value Question
Post by: PRR on January 16, 2019, 05:10:45 pm
> I know AC15s ...only use a 500ma fuse

500mA in 230V land.

1 Amp in 117V land.
Title: Re: Fuse Value Question
Post by: jjasilli on January 16, 2019, 08:05:14 pm
Seems there are different versions of the AC-15 schematic showing 1, 2 , 3A mains fuses:  https://el34world.com/charts/Schematics/files/Vox/Vox_Schematics.htm