Naim NAIT 2 Restoration Project

[hifiaf]

A few more tweaks added -- all the above and some extra material on setting bias, including a video.

 

[Bad Parameter]

A few more tweaks added -- all the above and some extra material on setting bias, including a video.

On an undertaking of this scale it's important to add a light/dim bulb limiter to the start up procedure, plenty of links out there explaining. A socket spliced into an extension cord with wire nuts is plenty fine. In this day and age might need to mention must be incandescent, Edison base halogens should work, I never tried. Hopefully save some Naits for the next generation of fiddley monkeys to let the smoke out.

 

[Jo Sharp]

After a looooong delay, I started on this project a few days ago and have completed phase one:

Vishay 50V 10,000uF power psu caps
Vishay 3300uf 25V pre psu cap
feedback caps (pwr and pre) Nichicon Muse 50V 47uF
cleaned up heat sinks and applied new paste
cleaned 2A fuse
isolated the phono stage power rails

DC offsets 11mA and 9mA - so all good.

After a short test run with an old drive unit, hooked up to the 2805 ESLs, running off a phone with Helm Bolt dac.

Sweet music! Even without any running-in, this is going to be a keeper for sure.

Phase two - planning 2 x ALW psu boards for the pre section. And the xtra decoupling caps on the output trannies as recommended on Acoustica.

 

[martin clark]

Nice project; and nice to see you post here again @Jo Sharp : )

Only one suggestion - you might want to consider changing the 6A/100PIV bridge rectifier when you next have it apart. They don't last forever - the symptom is fuse-blow on turn-on. Fortunately you can still find drop-in replacements pretty cheaply, so grab a couple.
ATB.

PS: Oh, and the preamp section draws so little current, I'm perfectly happy with one ALWSR for the whole front end, no need for one per channel; it's better to give one a little more load. Is this change worth it?.. not sure, but I had a spare all those (15+!) years ago - which is why I went there.
Adding a bit of output transistor decoupling, say 100uf + strapped back to the transformer centre tap as ilustrated, did more.

You've inspired me - I need to pull my Nait 2 out of the cupboard, and try it once again; maybe even service it!

 

[Jo Sharp]

Hi Martin,

thanks for your kind words and helpful (as always) suggestions. I will follow them of course.

one interesting point: the NAIT 2 has a 0V line from the PCB via the earth terminal on the back to the mains lead earth. So if you use a Naim CDP you will end up with 2 joined connections to earth which is not regarded as a good idea.

 

[coltrane]

...Only one suggestion - you might want to consider changing the 6A/100PIV bridge rectifier when you next have it apart...

how about replacing that rectifier with 4 diodes instead? generally and IME, it benefits in better musicality (and in the other hi-fi attributes, as well)

 

[martin clark]

Only tiny space allowance - about 18 x 18mm.

- and there;s no much wrong with the original, imo.

 

[coltrane]

Only tiny space allowance - about 18 x 18mm.

- and there;s no much wrong with the original, imo.

positioning them vertically is doable. and yes, no problem with the original rectifer, agreed - but here the aim is better sonics, ain't it

 

[martin clark]

Naits are about 'enjoyment' - rather than 'accuracy', I suggest.

You do what works, for you

 

[Jo Sharp]

Jo - seriously - don't butcher the amp. PM me - I'll buy it from you.

I have not changed anything that can’t be undone. I even have a bag of NOS Roe caps should they be needed.

 

[Pete MB&D]

I changed a faulty one and all I had was a chunky one I had to drill out the holes a smidge and the user said it had never sounded so good.

Pete

 

[jpk]

Another huge win - if you find it has too much gain then snip the 1k resistor in line with the 47uF feedback cap in the preamp. The gain stage is now a buffer instead and can use far more of the not-very-well-tracking volume pot.

Can I do this also to the NA321 or even to a Starfish?

 

[The_JJ]

Interesting Pete, there's no 317 that I can find...there’s just the large 2700uF axial cap on the pre-amp rectifier diodes output which feeds both channels.

It's a tiny TO92 with 2 tants next to it

 

[The_JJ]

Can I do this also to the NA321 or even to a Starfish?

You can, although replacing it with 3k3 might be a better compromise.

 

[laverda]

If I can pile in: I was looking at this last week (see photo) and wondering if it was worth some time to get up and running. A few bits missing Vol and balance pots (blue alps will not fit) and some output transistors.. Then I stumble on this thread...sounds like it's worth a little TLC, all be it a Nait 1

Anyone know where I can source a Vol pot that would fit and best modern outputs if any.

TIA

 

[martin clark]

@laverda

Bring it!

ATB!

 

[Craig B]

If I can pile in: I was looking at this last week (see photo) and wondering if it was worth some time to get up and running. A few bits missing Vol and balance pots (blue alps will not fit) and some output transistors.. Then I stumble on this thread...sounds like it's worth a little TLC, all be it a Nait 1

Anyone know where I can source a Vol pot that would fit and best modern outputs if any.

TIA

Some have gone with mounting blue alps to the front panel upside down with short leads to the PCB.

Also, ISTR that if one were to remove the oddball one-channel balance control that there is an associated resistor that needs bypassing, else balance be way off.

 

[MJS]

The Alps blue does indeed just fit there if you put it upside down. I 3D printed a bushing so that it can lie centrally in the large panel hole. You'll need a large washer on the front.

The heatsink clamp needs splitting equally into two. This keeps constant pressure on the output transistors. As it is it can bow and not clamp the inside ones as heavily. This was a must-do mod at the factory.

And for goodness sake please replace that awful radial cap supplying the pre-amp. Axials are available still https://www.mouser.co.uk/ProductDet.../MAL202117332E3?qs=herSbFlu8j2m%2BUN59NsjgQ==

 

[Jo Sharp]

And for goodness sake please replace that awful radial cap supplying the pre-amp. Axials are available still https://www.mouser.co.uk/ProductDetail/Vishay-BC-Components/MAL202117332E3?qs=herSbFlu8j2m%2BUN59NsjgQ==

Used exactly that cap. Now wondering about the CCS mod.......

2 days of warm up and the sound is just lovely. Running off the CDS3 and into ESL 2805s, which of course this puny little box shouldn't be able to drive..but does brilliantly. Just for fun, tried a few tracks from Rufus du Sol ; the deep bass lines on Desert Nights or Innerbloom were managed very well, even if not at NCC300 levels of control.

I remember a visit to Naim HQ in the late 90s and noticed (IIRC) in JV's office a NAT tuner with Nait and IBLs. So it can't have been that bad....

 

[laverda]

Taking a closer look at my unit, it has been recapped at some point in its life, having Elna, Nichicon and OScons installed along with uprated rectifiers. I recall OSCons were a favorite back in the day but I found them a bit soft and so I'll be swapping them back to bead tants.

May not be a big job as long as the transistors are OK ? I'll whip round and test these and the caps before I get excited.