I want to put a HT fuse in a new design, but I can't decide whether I should make it user accessible or not. I intend to sell the amp, and I'm just trying to anticipate what would happen if the fuse ever blows.
On the one hand, if the fuse is inside the chassis, the user won't be able to mindlessly replace it, and will need to take it to a tech. I'm assuming that if the fuse blows there's something seriously wrong.
On the other hand, if the fuse is user accessible, it's easier for the user to check if the fuse is blown (to inform me or the tech), and easier for the tech to check himself. Of course, there is the risk that the user will replace the fuse thinking there's 'something wrong with the fuse', or use the incorrect value.
What do you guys think?
HT fuse - inside or outside?
Moderators: pompeiisneaks, Colossal
Re: HT fuse - inside or outside?
I've been leaning towards starting to mount them internally.
Like you say, if the fuse blows, the amp should probably go to a tech anyway.
Putting it on the outside carries the risk that the user will electrocute themselves on it, or replace it with a piece of tin foil, plug it back in and do some real damage.
Seems like a low upside/high downside situation to me.
Like you say, if the fuse blows, the amp should probably go to a tech anyway.
Putting it on the outside carries the risk that the user will electrocute themselves on it, or replace it with a piece of tin foil, plug it back in and do some real damage.
Seems like a low upside/high downside situation to me.
Life is a tale told by an idiot -- full of sound and fury, signifying nothing.
...in other words: rock and roll!
...in other words: rock and roll!
-
JamesHealey
- Posts: 477
- Joined: Thu Aug 28, 2008 5:34 pm
- Location: Leeds, UK
Re: HT fuse - inside or outside?
It's safer for all if the fuse is on the outside! Means you don't have to go near those big filter caps that can shock you! The fuse is there to protect people first! At least that's my opinion
-
David Root
- Posts: 3540
- Joined: Fri Aug 04, 2006 3:00 pm
- Location: Chilliwack BC
Re: HT fuse - inside or outside?
I put 'em on the outside, same as Marshall.
Re: HT fuse - inside or outside?
This is funny, Last night the same thought crossed my mind; conclusion outside mount.
1968 Marshall iron and fuse holders.
1968 Marshall iron and fuse holders.
You do not have the required permissions to view the files attached to this post.
Re: HT fuse - inside or outside?
Just playing Devil's advocate, if the there's proper bleed resistors on the caps, wouldn't that be safer to mount it internally then? There's no way they wouldn't discharge by the time the amp gets out of the chassis. Plus, I'd hope a tech would know enough to not injure themselves!It's safer for all if the fuse is on the outside! Means you don't have to go near those big filter caps that can shock you! The fuse is there to protect people first! At least that's my opinion
Thanks a lot for the responses, I'm still undecided, however...
Re: HT fuse - inside or outside?
+1 for outside accessible - quicker (and safer) to check.
Re: HT fuse - inside or outside?
Ht fuses sometimes blow just for the hell of it, stress from the stby or power up. Occasionally one pops and I think oh no, but the amp's always fine. Glad it's on the outside.
-
guitarmike2107
- Posts: 303
- Joined: Fri Dec 12, 2008 10:51 pm
- Location: East Scotland
- Contact:
Re: HT fuse - inside or outside?
You need to decide if you want the user to be able to replace the HT fuse or if it’s a Service technicians job only.
It is assumed there will be a marking to say no user serviceable parts inside?
The advantage of putting them externally is
They are easy to access
Can be checked and replaced by anyone… even a drummer could do it!
The disadvantage is
Guitarist are also dumb,.
The wrong spec of fuse may be used, which may cause fire, shock or further damage, which you may be asked to cover under warranty.
Advantage of installing them internally
They should only be checked and changed by a qualified person per your instruction marking.
A “qualified person” can take the time to properly check over the amp before starting it up again, checking valves shorts etc.
A qualified person would certainly use the correct part and therefore prevent further damage or a risk of fire or shock in the future.
You can easily place 2 fuses on the AC side before the rectifier without having loads of holders on the outside. See link http://www.freewebs.com/valvewizard/fuses.html
How often do fuses just blow for the fun of it….
You can fit a drain resistor to ensure the amp is safe when opened.
The disadvantage of internally is
Your roadie wont be able to change the fuse quickly if it pops on stage, ( but that’s what back up amps are for anyway)
Adventurous guitarist will open the amp up to see what’s wrong (but you have told them not to)
You cant ask him to check the fuse when he phones up from the other side of the country to say the amp is not working… now what do you do?
Of course all the guys here will want it external, we build/service the things.
BTW Marshall place fuses internally and externally, depending on the circuit.
You decide.
It is assumed there will be a marking to say no user serviceable parts inside?
The advantage of putting them externally is
They are easy to access
Can be checked and replaced by anyone… even a drummer could do it!
The disadvantage is
Guitarist are also dumb,.
The wrong spec of fuse may be used, which may cause fire, shock or further damage, which you may be asked to cover under warranty.
Advantage of installing them internally
They should only be checked and changed by a qualified person per your instruction marking.
A “qualified person” can take the time to properly check over the amp before starting it up again, checking valves shorts etc.
A qualified person would certainly use the correct part and therefore prevent further damage or a risk of fire or shock in the future.
You can easily place 2 fuses on the AC side before the rectifier without having loads of holders on the outside. See link http://www.freewebs.com/valvewizard/fuses.html
How often do fuses just blow for the fun of it….
You can fit a drain resistor to ensure the amp is safe when opened.
The disadvantage of internally is
Your roadie wont be able to change the fuse quickly if it pops on stage, ( but that’s what back up amps are for anyway)
Adventurous guitarist will open the amp up to see what’s wrong (but you have told them not to)
You cant ask him to check the fuse when he phones up from the other side of the country to say the amp is not working… now what do you do?
Of course all the guys here will want it external, we build/service the things.
BTW Marshall place fuses internally and externally, depending on the circuit.
You decide.
Re: HT fuse - inside or outside?
One option is to mount the fuse externally, but to add another fuse internally (in series) which is larger than the external one (say 2x the current rating). That way if the smaller fuse blows by accident it can be replaced quickly by the user, but if they replace it with a bit of tin foil you still have the internal fuse to prevent a serious fire hazard.
-
JamesHealey
- Posts: 477
- Joined: Thu Aug 28, 2008 5:34 pm
- Location: Leeds, UK
Re: HT fuse - inside or outside?
merlin your genius never ceases to amaze me!
-
Cliff Schecht
- Posts: 2629
- Joined: Wed Dec 30, 2009 7:32 am
- Location: Austin
- Contact:
Re: HT fuse - inside or outside?
That's very practical advice for sure.
**golf claps heard all around**
**golf claps heard all around**
Cliff Schecht - Circuit P.I.
Re: HT fuse - inside or outside?
Heh, it's not my genius! Lots of appliances do this, including many Garnet amps.JamesHealey wrote:merlin your genius never ceases to amaze me!
Re: HT fuse - inside or outside?
(deleted)