Blowing Fuses on DR Power Supply
Posted by: John G on 17 January 2015
Hi..is there anyone else having the same problem as me..I have now blown 3 line fuses in the past year on my DR Power Supply (attached to NDX) when switching on.
https://forums.naimaudio.com/to...22#19447375214204422
Naim have found that fuses of the same rating but different manufacturer do not provide the same outcome when used in Naim units.
In Production and Service we use fuses from a specific series within the Littel Fuse Company range. We strongly advise you continue to use the exact same as replacements.
These should be readily available from your Naim retailer – although some will source their stock elsewhere. You should check that your Naim retailer carries a full range of spare fuses – either from Naim Salisbury or the exact same items from a Littel Fuse supplier.
Fuses of the correct rating from other manufacturers may work and should be safe. However, some Naim units make greater demands on the rating (the XPS-2 for example) and non-Littel fuses are likely to rupture – always or more often.
Repeated blowing of the correct Naim supplied fuse is an equipment fault indicator.
Repeated blowing of A.N.Other (correctly rated) fuses MAY be a fuse fault indicator.
The XPS has a reputation for blowing fuses
I have friends with the original (black) XPS & XPS2 & both have the same problem. They leave them switched on 24/7 & only turn off when going away for holidays etc.
A question for Naim ........
Looking at fuse ratings & input power VA for various PSU's, something does not appear to be logical.
555PS
Input power 80VA
Fuse T3.15AL
SuperCap
Input power 40VA
Fuse T2.5AL
XPS
Input power 110VA
Fuse T2.5AL
HiCap
Input power 40VA
Fuse T3.15AL
Repeated blowing of the correct Naim supplied fuse is an equipment fault indicator.
Actually, in the case of the XPS2, as many have noted, it's an equipment design fault indicator.
The XPS2 is the only piece of electrical equipment that I have ever owned that has blown a fuse apart from a kettle... and it's done it several times. Its a design flaw and maybe Mike-B's post gives an indication of what the issue is.
Oh I wouldn't say that 
or would I ??? 
The XPS2 is a bugger for blowing fuses. Mine got through 2-3 a year and I kept a bag of dealer supplied spares. I suppose it comes down to how often it blows a fuse when powered up. I'd say three a year sounds OK but if that is the same as the total number of times it's been switched on in 12 months then there is a problem. My 500PS has also blown a fuse once in 2 years through probably >20 power cycles. Being convinced about how seriously Naim treat sonic performance and the lengths to which they go, I'm happy to stick to their stock fuses and keep spares. I've never been charged for them.
A question for Naim ........
Looking at fuse ratings & input power VA for various PSU's, something does not appear to be logical.
I suppose they may have the figures wrong - or you lack the specialist knowledge to encompass the variations in characteristics that choices in transformer design can produce.
If so - a question of education that you could address..
As someone with B.Sc & few years in the electrical business I find it a perfectly reasonable & logical question & was hoping that Naim might respond.
Meanwhile welcome to my ignore list, you're in an exclusive club of one
Hi..is there anyone else having the same problem as me..I have now blown 3 line fuses in the past year on my DR Power Supply (attached to NDX) when switching on.
Yes, xps2 yesterday when upgrading the ndx firmware. Grrr
A question for Naim ........
Looking at fuse ratings & input power VA for various PSU's, something does not appear to be logical.
555PS
Input power 80VA
Fuse T3.15AL
SuperCap
Input power 40VA
Fuse T2.5AL
XPS
Input power 110VA
Fuse T2.5AL
HiCap
Input power 40VA
Fuse T3.15AL
Na 110v xps2 fuse 240v 5al. They (naim) should bung at least a dozen in the box given its' propensity to eat them , especially at the most inopportune moments ....
Hi John,
My 500PS is twitchy in this regard. Try this. It sounds daft, but seems to help.
When pushing the power button; jab it quickly as opposed to a 'soft push'. This seems to make the connection more quickly, and there is less chance of the case fuse popping.
John.
Hi John,
My 500PS is twitchy in this regard. Try this. It sounds daft, but seems to help.
When pushing the power button; jab it quickly as opposed to a 'soft push'. This seems to make the connection more quickly, and there is less chance of the case fuse popping.
John.
Not daft at all. I always had to sneak up on my xps2 when switching on to avoid blowing case fuses.
Hi John,
My 500PS is twitchy in this regard. Try this. It sounds daft, but seems to help.
When pushing the power button; jab it quickly as opposed to a 'soft push'. This seems to make the connection more quickly, and there is less chance of the case fuse popping.
John.
My 500PS blew it's fuse a couple of weeks ago.
I always turn the volume knob right down but still get a hefty plop-sound though the sibbles every time. It causes some fear and trepidation at button push time.
Do you think it would help to push the mute button on...?
[i haven't tried yet, and don't have any spare fuses so don't want to]
Or wear ear-defendors...?
Or unplug the sibbles naca5 before turning amp off... ?
[seems like a lot of trouble to go to]
I've just got used to it. I had an Exposure amp that thumped loudly so the 500 is a trip down memory lane. Muting doesn't help. Our 300 did it also, but rather politely compared to the 500.