Had to disconnect my equipment the other day and neary s*** myself when it wouldn't power on
turned out to be fuse in XPS. So now using spare and all ok
Have read a few articles about fuses going but I want to try and minimise it occurring again, so want to be very clear on power off and on order
I have NAC N 272 XPS and NAP 250 DR. If I read right power off is speaker to source so Nap 250 off first, but is it then the XPS with the power cord in and finally the 272 or the other way round I.e 272 then xps ?. And reverse for power on again is it 272 first and nap 250 last?
obviously will get some proper maim fuses to replace the blown one but I don't want another heart attack !!
Posted on: 22 February 2017 by Mike-B
You do not have the 272 connected to mains power when XPS is used, all the power is from XPS. ... See Connection Guide page 22
The power off cycle is 250 off first - then XPS (272)
The power on cycle is XPS (272) on first - then 250
Posted on: 22 February 2017 by David Hendon
I don't think the power switch on the 272 does anything at all if you are using an XPS-DR and so the 272 has its link out, a Burndy connected and no power lead.
We aren't allowed to discuss fuses here (forum rules) but they do blow occasionally and there is nothing you can do about it except keep some spares, which should be the correct value and the correct type, which probably means buying them from your Naim dealer. You are even supposed to put them in a particular way round, for the correct sound quality........
i really doubt it was anything you did wrong. Just bad luck that you turned the unit on at the moment that the AC supply was at or near a maximum. There is no way to avoid that.
best
David
Posted on: 22 February 2017 by Mike-B
The 272 on/off switch does nothing when its powered by XPS - its the very first thing in the units power circuit before the 272's internal power supply. When the 272 Burndy plug is removed & the XPS connected, that whole power supply section is isolated. The XPS simply replaces the 272 internal power supply, the 272 itself consumes very little power & there is no means or need to turn the 272 off.
The fuse blow problem you had is simply the XPS transformers in-rush current phase that lasts a few milliseconds at power up, once this phase is over the power consumption is normal. The in-rush phase is why its important to have the correct slow blow fuse as specified by Naim for the XPS, the slow blow feature allows high in-rush amps for a short period without rupturing (hopefully) .
Posted on: 22 February 2017 by ChrisSU
Tha XPS has a reputation for blowing fuses, and some users keep a supply of the correct slow blow fuses for that reason. Presumably you used the correct fuse stored in the spare fuse holder in the rear panel, not just any old fuse that fits?!
You are using the correct switch on/off sequence, other than that the 272 should have its mains lead removed, and its on/off switch is then a vestigial feature that can be ignored.
When you turn the units on or off (250 as well as XPS) press the button firmly and release it quickly to minimise the risk of a blown fuse or tripped MCB. I also turn the volume to zero and mute the preamp.
Posted on: 25 February 2017 by audio1946
theres no black magic. on switch on the magnetic field strength increases which slows down the current increase . AT switch off the current spike across the switch causing arcing . then fuse is more likely to fail. It could also fail if the mains switch is not positively switched on , switch contact bounce OR the fusing element just gets tired after old age
