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Naim XPS DR. To leave on or to not leave on. What do you do?

jimmymcfarrell

pfm Member
Having recently bought an XPS DR (thankyou topbloke @justin65, I hope you have forgiven me :) ) and discovered they have a bit of an appetite for fuses in the mains input, I’ve been wondering what other owners do? Mine has eaten 2 fuses so far in as many weeks. I haven’t checked the voltage coming out the wall but if it’s anything like my last place it could easily be well up near 250v so this could be a factor.
Do others just leave them switched them all the time? This isn’t really an option for me and seems like a ridiculous solution, especially when it will often go multiple days at a time without use.
I’ve seen it suggested that some people up the fuse size to 3.15a (from 2.5a). This is listed as a definite no no on the green forum with warnings that it will kill you & your family & everyone within a 3 mile radius when it explodes. I’ve seen discussion that what it really needs a fuse size that doesn’t exist, in between 2.5a & 3.15a so my thinking is that under fault conditions it’s going to pull more that 3.15a for the time it takes for the fuse to blow, so is upping the fuse size by just over half an amp really such a bad thing if it stops the nuisance tripping?
I would be interested to hear what others think about this.
 
Leave the fuse at the recommended rating or you will invalidate your house insurance if anything goes wrong.
Fuses should not be blowing weekly.
Get it looked over.
And I turn my Naim kit off every night when I go to bed.
 
Seems it's a known problem if you look it up on the naim forum. Apparently it can be worsened if the iec fitting that plugs into the back of the unit is a bit sloppy. Try a different mains chord?
 
Inrush current on Naim amps is long standing problem, or feature in Naim land. I think it's laughably poor design, but there you go.

Some even use special MCBs in their consumer units to avoid the constant tripping.

I'd try a Teddy or CHC power sipply.
 
Seems it's a known problem if you look it up on the naim forum. Apparently it can be worsened if the iec fitting that plugs into the back of the unit is a bit sloppy. Try a different mains chord?

Yes I will try this.

I don’t think the unit is at fault - well the design is at fault not my particular unit - because there is discussion of this being a well known problem. It sounds like the fuses are right on the limit of suitability at best - if my mains voltage is high & I'm using a slightly loose fitting mains cable it sounds like that could be easily provoke the fuse to blow.
I’m sure it’s obvious to people but I’m not talking about the fuse blowing randomly during use, it only happens on startup. I’ve seen it said that pressing the on button a bit limply can cause it to blow; as can switching off and on again in quick succession. If it didn’t make the NAC-N-272 SO MUCH better I wouldn’t be putting up with this
 
Known issue.
Naim or maim dealers can supply fuses that are suitable but a bit more robust at the correct rating. Dont know how. Specific manufacturer ?
I switched my old cds3 on once a week. Would blow one of these fuses about every 6/7 months or so.
I think class A can supply them at a cost. When I got my old xps2 serviced there I asked for a bag of 5 extra fuses too.
 
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It’s not the voltage that causes this it’s the inrush current. Newer kit has a soft start circuit that prevents it but the old XPS is old school. You must use exactly the specified fuse rating and manufacturer but if you are switching off and on regularly then you can’t avoid it. I leave mine on all the time mainly because out of laziness I leave my other kit on too. I heard all the theories about how to push the on button but ultimately the fuse gets stressed every time it’s powered up. Best thing is to leave it on or as suggested above try another PSU like the Teddy XPS.

If you are really concerned, I’d give Peter at Cymbiosis a call. He’s as respected a dealer as you will find and he regularly posts in the Naim forum.

Here is the correct fuse (£1.50):
https://www.cymbiosis.com/product/naim-antisurge-glass-fuse-t2-5al250v-single-supercapxps2/
 
Seems it's a known problem if you look it up on the naim forum. Apparently it can be worsened if the iec fitting that plugs into the back of the unit is a bit sloppy. Try a different mains chord?

If it fits and is powering the unit, it's not the mains cable. IEC cables are rarely 'loose'
 
Fuses don't get 'stressed' they either conduct electricity or don't. Why would anyone leave something on nowadays?
Fueses get stressed when the power is swtiched on its the inrush current heats the wire in the fuse and untimate weakens it and it will fail.

Pete
 
Fueses get stressed when the power is swtiched on its the inrush current heats the wire in the fuse and untimate weakens it and it will fail.

Pete

It's not a lightbulb mate, there's something wrong with the amp if it's continuously blowing fuses. Funny how fuses can last for decades unless they blow?

BRB replacing the fuse in my kettle. It's getting 'stressed'
 
It's not a lightbulb mate, there's something wrong with the amp if it's continuously blowing fuses. Funny how fuses can last for decades unless they blow?

BRB replacing the fuse in my kettle. It's getting 'stressed'
I will stop replying as you don't seem to know anything about electronics so I am not going to suceed with my explanions.

Pete
 
As the BBC put it, our role is to educate and inform. :). So here we go…..

“Fuse fatigue is a factor due to current pulses that cause heating/cooling (expansion/contraction) cycles of the fuse element. A fuse not only has a current rating, it has a current pulse rating, known as the I2t rating -- this rating determines the amount of heat energy required to melt the fuse element in a single pulse of current before any cooling can take place -- for through-hole and clip type electronic fuses, this time is 8ms.

The fatigue limit on I2t, if you will, depends on the fuse element material -- zinc-based elements have a high coefficient of expansion and a low melting point, so they are more prone to fatigue failure than the silver or copper elements used in today's large fuses as per this Bussmann note. For smaller fuses, which likely still use the zinc alloy elements for cost reasons, a max repetitive pulse I2t of 20% of the fuse's rated I2t is recommended by Littelfuse.”
 
*science*

There's something wrong with the amp, no need to leave it on. Why are we worrying about fuse stress when there's non user replaceable items in the actual amplifier? If it's blowing fuses continuously there is a problem with the amp. It's not 'fuse stress'
 


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