NAP 500 Blown Fuse

I was replacing/upgrading interconnects with power off. After new cables were in, I powered everything up. The 500 wouldn’t come up. I checked all cabling including the powerline. I made sure the power line was making good contact at the 500 when there was a large flash of light. I had a blown fuse. Replaced the fuse the 500 came back up. However the 555 door does not close completely. I am also concerned about the preamp because my tuner won’t play through the 552. I have replaced all fuses for all power supplies. Everything is powered but nothing works.

I understand that the power line connection can blow fuses. I went to my dealer and got some more fuses as spares. The fuses I received were different. Some had a fine element, others were heaver guage and spiraled.

I’m new to the forum, any ideas?

What a fun upgrade. Still haven’t heard my new cables.

If it’s a non-DR 500 then it’s a common occurrence apparently.

My non-DR happily eats fuses for breakfast lunch & tea.

My strategy is to only power down the 500 when need be, and have a stash of spare fuses ready and waiting.
The last fuse i put in the 500 has lasted at least 6 switch off and ons so quite a good innings! :smiley:

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Yes, you need to be careful with the Powerline that it is pushed all the way in. The jaws are very stiff so they make the most secure connection, so you need to push beyond the first major resistance.

Naim use T fuses. The correct rating is printed on the rear panel ( and will differ depending on what voltage your kit is set at).

Really? I’ve never come across that with any of the 500s I’ve used it even owned.

The XPS2 though…,

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I should have said it is a DR’d 500

My CDX2 likes to eat fuses, so I never ever turn it off…



I’m sure the problem originated with power line but I don’t know what to do now. All fuses have been replaced and power line replaced with a different cable. Everything powers up but now I’m afraid the 555 and the 552 have been damaged.

Have you recalibrated the CD555 Lid?

Maybe the blown fuse has made the NAC552 go back to default input assignment? Have you tried checking the input assignment or just trying the tuner on a different input quickly to check.

That’s okay, you can disregard my post then! :slightly_smiling_face:

There were posts about this on the old forum.
As well as the non-DR 500 tendency to blow fuses while switching on, the introduction of DR’ing the 500 eliminates the huge speaker-WHOMP! on switching off, and when switching back on (apparently).

Fortunately one can buy many thousands of fuses for the enormous price of DR’ing a 500 :upside_down_face:

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Thanks Richard. I tried to recalibrate the 555 door without success. It won’t close all the way.

I tried changing the tuner to a different input on the 552, still doesn’t work.

Richard, how do you change the input assignment on the 552?

It’s in the manual. As follows;

4.2 Input Socket Assignment

Any NAC 552 source input socket can be selected by any button. For example, while the NAC 552 default setup is for the cd input button to select input socket No. 2, custom programming of input assignment could enable any input socket to be selected by pressing the cd button. Assigning of each record button follows the corresponding source button.

Input assignment setup is accessed through the NAC 552 program mode. To switch into (or exit from) program mode press and hold the prog key on the NARCOM 4 remote handset (in preamplifier mode). Program mode is indicated by a flashing indicator on the front panel volume control and the record selection indicators extinguishing.

Note: If no function is operated within five minutes of entering program mode the NAC 552 will return to normal mode automatically.

Any of the six source buttons on the front panel can be assigned to any of the nine stereo inputs (seven DIN sockets and two RCA Phono socket pairs) on the rear panel. In program mode, as a source input is selected, a rear panel indicator will illuminate to designate the socket to which it is assigned.

To change the input socket assigned to a source button, select the source button and use the front panel record mute and mono buttons to scroll along the input sockets. If the input socket selected is already assigned to a source button the indicator above the socket will flash repeatedly. It is possible
to assign one input socket to more than one source button but NOT to assign multiple input sockets to one source button. The remote handset record mute and mono functions can also be used to set up input assignment.

To exit from program mode press and hold the prog key on the handset until the record select indicators are restored and the volume indicator stops flashing.

Table 4.3 illustrates the NAC 552 default input assignment.

I’ve sorted out the connections. The tuner is now working.

Calibrating the 555 door is a work in progress. The door won’t close all the way. I manually (gently) close the door and start the calibration releasing the door. I’ve tried many times to make sure I’m doing it right.but the door keeps returning to about a third open.

Thank you so much for your time and effort helping me.

Good news Dan on the 552. I’m sorry I cannot help further on the door. I hoped that it would just need recalibrating. Maybe try again, or else give your dealer a call in the morning, unless any current or past CD555 owners have any better ideas here.

I’ve only had a door issue once when our cleaner inadvertently triggered the door open and tried to manually close it again. The door fouled on the casing. I performed a door reset and calibration. This resolved the issue and it has been fine ever since.

Hi Dan,

Just to add, if your 555PS is the DR version, you need to keep the relevant button(s) on the CD555 held for a good 3 - 4 seconds after switching the PS on during the recalibration process.

This is because there is a slight delay in the voltage rails coming up on the DR model.


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After multiple attempts at recalibraton of the 555 door, my wife suggested I leave it alone for the evening. Always good advise when problem solving. Next morning the calibration worked on first try. I hate when my wife is right. Everything is sorted out and I’m listening again. My dealer wants to have a look at the power line to see if something is defective. Thaks again.

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Good to hear that Dan, thanks for the update.

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