Nait 2 - to service or not? Remixed

Posted by: Craig B on 13 March 2004

Sigmund
Member
posted Tue 09 March 04 17:02

I'm the proud and original owner of a Nait 2 integrated amp. On and off, I think about sending it in to be checked out and serviced as needed. A couple of years back, I spoke with a tech at the Chicago site who said that as long as it wasn't giving me any trouble, I should call back in another ten years. Last year, I called again and I could hear the guy on the other end of the phone drooling at the thought of getting $450 or my hard earned dollars because nothing less than a complete overhaul would do. What have any other Nait 1 sor 2 users done? I don't want to give away my $$ unnecessarily. On the other hand, while my unit sounds *great* to me, I don't think I'd know if it's slipping a little. Thanks.

Posts: 75 | From: Pittsburgh, PA USA | Registered: Wed 16 January 2002

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PR
Member
posted Tue 09 March 04 17:20

sigmund

I could rest your concerns if you want to sell your little Nait cutie?

Posts: 975 | From: RTW | Registered: Thu 25 July 2002

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Sigmund
Member
posted Tue 09 March 04 18:18

P, my long lost friend. I knew I could count on you to relieve me of my misery and compassion. Let's talk sometime, say, after another 35 years or so when my wife and I are so old that we couldn't tell the difference between our trusty Nait 2 and a can or okra. Stay in touch.

Posts: 75 | From: Pittsburgh, PA USA | Registered: Wed 16 January 2002

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Top Cat
Member
posted Tue 09 March 04 19:00

It's well worth having the Nait 2 serviced - it can be an incredible injection of musicality and life into the wee amp - but $450 is a severe case of taking the piss. I'd reckon no more than $150 - I paid £40 to have mine done, including new caps, display, power chord, a good clean and some other bits & pieces. That translates to around $80.

John

Posts: 2127 | From: The Fife Riviera | Registered: Tue 24 October 2000

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PR
Member
posted Tue 09 March 04 20:29

Top Cat

Do you want to sell yours?

Posts: 975 | From: RTW | Registered: Thu 25 July 2002

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Sigmund
Member
posted Wed 10 March 04 02:37

Top Cat, did you have yours serviced by a dealer or by the distributor? Thanks.

Posts: 75 | From: Pittsburgh, PA USA | Registered: Wed 16 January 2002

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Top Cat
Member
posted Wed 10 March 04 07:45

Mine was serviced by a Naim approved dealer using the Naim Nait2 update 'kit'. My Â£40 price may have been subsidised by the fact that I was also having an Armageddon, Cirkus and Helikon added to my LP12 at the same time - so perhaps I got the Nait kit at cost?

John

Posts: 2127 | From: The Fife Riviera | Registered: Tue 24 October 2000

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Top Cat
Member
posted Wed 10 March 04 07:47

quote:
Do you want to sell yours?

No chance

Anyway, it's technically my wife's - the 52/SC/250 is mine. I could sell it and make a tidy profit but then I'd regret it, I am sure of it...

John

Posts: 2127 | From: The Fife Riviera | Registered: Tue 24 October 2000

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PR
Member
posted Wed 10 March 04 08:45

Top Cat

I envy you. We have a 62/140 in the bedroom, which is largely used by my other-half. However, with selling my main system, I need a short-term plug. I'm considering the Nait5i - new sound and all that, but wonder how it would compare to the Nait 2? The 5i certainly loses on cutie looks IMO.

Posts: 975 | From: RTW | Registered: Thu 25 July 2002

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mykel
Member
posted Wed 10 March 04 16:38

Just an FYI for Canadian's

I just received a reply from Jean-Luc at Dimexs regarding recapping my Nait 1.

Quote

The cost is 278.00 including parts and labor but no shipping and tax(es).
We change 17 capacitors and reset the bias.

Endquote

I also got a quote on my 160 - same deal, excluding taxes and shipping - $434.00 Canadian.

This is on March 10, 2004.

regards,

michael

Posts: 271 | From: Citizen, Planet Earth - The Canadian Part Eh!! | Registered: Thu 18 January 2001

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Craig Best
Member
posted Wed 10 March 04 16:25

Hmmm, I only paid $Cdn 300. for my 1985 edition NAIT 1 just last year (a veritable bargain over here in Canada).

Spending another 300. plus dollars doesn't really appeal for what won't exactly be a fully restored amp considering that the key moving bits and connectors will all still be 19 years old.

For that matter, doesn't Naim HQ's service department change out things like DINs and speaker output sockets as a matter of course should they appear to have seen better days? Shouldn't their distributor's service departments be also offering the same level of service rather than simply substituting new caps and re-setting bias? Or, is that what you asked for a quote upon Michael?

Thinking DIY for a moment, changing out the relevant caps appears a pretty straight forward job as long as one carefully observes correct polarity and properly re-mounts the output transistors with mica insulators and thermal coupling goo intact.

I wonder what's involved in re-setting the bias? The pots appear to be conveniently positioned atop the main board just aft of the output transistors. But, what of the relevant input vs. output values for the old NAIT? Presumably one needs little more than a decent scope and the relavant numbers to do the job properly. Anyone know the official details? (a PM will do thanks)

For that matter, what are the audible symptoms of out of spec bias voltage? I've heard tell of the odd younger amp going off and needing nothing more than a bias adjustment. Perhaps such adjustment accounts for much of the perceived improvement brought about by a full amplifier service?

Any thoughts?

Craig
Posts: 600 | From: Canada | Registered: Mon 31 July 2000

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mykel
Member
posted Wed 10 March 04 20:27

Craig

I believe I used the phrase " service / re-cap ", figuring on my end that would entail the full monty.

It was mentioned that Target HiFi may be willing to do the service, If so, Dimexs would send down the cap's but they would have to do the bias adjustment. From this I would take that the service is just what you mentioned, the re-cap and bias check. (unless other work is specified or visual inspection indicates otherwise?)

Does seem kinda steep, if I remember correctly I picked up the wee beastie quite a few years ago now for the unheard of sum of 400.00 CDN, and that was off of the Naim dealers "previously enjoyed" section.

Problem is as mentioned on phone the other day, I just lost a channel, and it is the amp unfortunately. Maybe I will ring up Target and see what they have to say. Beats postage and the wait-time....maybe....

regards,

michael
Posts: 272 | From: Citizen, Planet Earth - The Canadian Part Eh!! | Registered: Thu 18 January 2001

Posted on: 13 March 2004 by Craig B

Sorry to hear that it is actually the amp that is faulty Michael.

Let me know if you do decide to go for the servicing at Target, as I'd like to be a fly on the wall whilst Allan has a go at it.

In particular, I am curious as to what the re-biasing procedure entails, as I believe that my 1 may be out as the wee beast appears to think that everyone should speak and sing with an abundance of sibilance of late (kind of like what your old Scanspeaks were superimposing on the proceedings prior to your fitting the Neodymiums). Also, as I mentioned on the telephone, the level of noise through the speakers seems somewhat higher than usual for the breed.

Come to think of it, perhaps Al can give my bias pots a tweak on your tab?

Craig

Posted on: 14 March 2004 by Mr.Tibbs

Craig,
I imagine service centres probably use some kind of distortion analyser to set the output bias. The idea is to provide just enough forward bias to minimise crossover distortion, but not so much that the output stage is under risk of thermal runaway.

When transistors heat up, they tend to flow more current at any given forward bias, this in turn produces more heat, leading to more current. Before you know it, your little Nait will be trying to become a class A amp, with a lifespan of seconds.

Most designs (including Naim) use low value resistors in series with the transistor outputs. These help protect against thermal runaway by virtue of the voltage across them increasing as the current through them tries to increase. This provides a self limiting effect, at the price of some increased output impedance.

Without access to a distortion analyser, you could get pretty close to the correct bias if you knew how much voltage should be present across the pair of output resistors, when the amp is correctly biased. Maybe they'd be prepared to share that info with you?

You'll need to use a digital Voltmeter, and make sure the amp is left to reach its normal idling temperature before testing. After making any adjustment, the amp shouldn't be running any warmer than normal.

As ever, proceed with caution when working inside a live amp!

Mr Tibbs

Posted on: 14 March 2004 by Martin Clark

quote:
you could get pretty close to the correct bias if you knew how much voltage should be present across the pair of output resistors, when the amp is correctly biased.

As a ballpark figure, a quick poke-about on two healthy Nait2s measured in the range 4.7mV - 6.5mV across each of the 0.22ohm emitter resistors.

Posted on: 14 March 2004 by Mr.Tibbs

Martin,
Check the voltage across the pair of resistors for each channel, and take a note of the values. Then, bring the lower channel up to the same value as the higher one. You'll find only a very small tweak of the pot is needed to shift the bias by a couple of mV.

Leave the lid off for an hour and keep and eye on temperature - there should be no significant change.

Have a listen. If it seems in any way worse, you can always go back to the original value.

Mr Tibbs

Posted on: 14 March 2004 by Martin Clark

Thanks Mr Tibbs, but been there, done that

Posted on: 14 March 2004 by Mr.Tibbs

"Thanks Mr Tibbs, but been there, done that

"

Sorry, I figured you had. I really just added that for Craig's benefit.

Go to it Craig!

Mr Tibbs

Posted on: 14 March 2004 by Martin Clark

Craig - Mr. Tibbs is right;and as for this bit:

quote:
What have any other Nait 1 sor 2 users done?

.

Um, well....

Posted on: 14 March 2004 by David Dever

Up to about two years ago, I did a good portion of the NAIT I and II recaps at NANA (Chicago). This service largely included any or all of the following:

- replace old with new-spec output transistors
- replace input transistors as necessary
- replace DIN sockets as necessary (corrosion)
- replace reservoir capacitors
- replace coupling capacitors with higher-spec bead tantalums
- modify grounding arrangement to comply with newer spec / later production etc.
- set-up and full test (NOT just a bias setting)

This is by no means a comprehensive list.

NAIT I units tended to be more fiddly than others inasmuch as the single-sided PCB had smaller copper traces, which would often pull away from the board EVEN at the proper worktool temperature settings.

As I recall, labor charges were the largest factor in the price - no "drooling" profit center for the technician poised to perform the upgrade service...

Posted on: 15 March 2004 by P

IIRC 7mV is about right on a Nait 2

P

Posted on: 16 March 2004 by Craig B

Thanks for your contributions gents.

I don't know what Sigmund and/or Michael intend doing with their NAITs, however, I think I'll hold off on making any decisions until such time as it becomes clear as to what constitutes a full service here in Canada.

Specifically, I'd like to know whether I should expect to get the same level/thoroughness of service as I would receive were I to send my NAIT off to Naim HQ?

Michael,

When you said...

quote:
It was mentioned that Target HiFi may be willing to do the service, If so, Dimexs would send down the cap's but they would have to do the bias adjustment.

did you mean that Dimexs would have to do the bias adjustment?

David,

Would it be safe to assume that NANA's NAIT 1 service would still be $US 450. regardless of what parts end up requiring replacement? Or, could it perhaps end up being greater or less than that amount?

On that note, would it be possible for you to post a copy of the complete service check list? (assuming it is considered kosher to do so)

Craig

Posted on: 16 March 2004 by mykel

Craig

Sorry about that, I meant that Target would have to set the bias.

Jean-Luc mentioned nothing about checking / replacing input or output devices etc. All he mentioned in his e-mail was Cap's and Bias.

When I get a moment I will send Jean-Luc a copy of David's post to see if Dimexs do the same type of service and if the price quoted was for said service ( less any needed parts of course ) or just the cost of caps / replacement / bias.

As my Nait is channel challenged at the moment I don't have much of a choice, either Target if willing or Dimexs.

Thoughts?

regards,

michael

Posted on: 16 March 2004 by mykel

Posted on: 16 March 2004 by Craig B

All things considered, I think I would go with Dimexs (or is it really Emmanuel at Euphonie?) assuming that they in fact do the full Monty as required.

Nothing against Target's potential abilities, but Emmanuel has the experience and David's mention of the board trace separation issue with the NAIT 1 in particular has me concerned (especially so as I was present when one of my speaker socket traces lifted during re-soldering at Target - and not through any negligence on their part I might add).

Also, it hasn't yet been established what exactly has caused your dead channel. Should said diagnosis be outside of Target's abilities, then you'll likely end up having to ship the amp to Montreal regardless.

Anyway, do let me know what you find out/decide.

Perhaps after one of them has had chance to practice on your half dead amp, I'll be more inclined to send my live one in.

Craig

P.S. Looking on the bright side, at least our old NAIT 1s will allow us each to test the Canadian service waters without putting our true loves (i.e. your 32-5/HI/160 and my NAIT 2) at risk.

Posted on: 17 March 2004 by Craig B

Well here's something interesting (at least to me anyway).

What got me thinking about having my old NAIT 1 serviced was a recent bout of persistent sibilance, susceptibility to RFI breakthrough and, higher than usual hum/noise through the speakers.

Just last night I was poking around (as I am want to do) and decided to swap out a cheap Freitag RCA to DIN (that had been doing temporary tuner connection duty of late) for a nice Chord Chrysalis RCA to DIN that was no longer seeing use in my modest all olive system.

Yes, you've guessed it, all the shite disappeared in one go. Bloody RF antennae that crap Freitag. In hindsight, I should have known all along - all classic symptoms for sure.

Anyway, there is still some residual low level hum through the speakers, but nothing more than is usual with the early NAITs (this system is in a small bedroom where such noise is quite noticeable, especially during late night listening at reduced volume).

Bottom line is that I won't be having this amp serviced anytime soon (knock on wood) other than perhaps treating it to new footwear, as it's original galoshes are well past it.

I will, however, be sticking to a regular schedule of internal visual inspections to ensure that none of the caps are suffering from bloat, nor have any taken to venting their spleen.

Thanks again to those who offered help/suggestions.

Craig

PS. Who the hell is using the Topic Rating feature again? Can't someone just turn it off all together?

Posted on: 18 March 2004 by Mr.Tibbs

Craig,
A new set of reservoir caps would probably kill the hum completely - as well as putting new life into the sound.

Don't wait until the caps belly out, they are shagged at 8 years or more, even if they don't look it.

Mr Tibbs

Posted on: 18 March 2004 by Sigmund

This is good news. Somehow, knowing more about what's involved sets my mind at ease. I suspect that I'll have it serviced during the next couple of months. I'll let you know about what differences .... Right now, though, everything sounds mighty fine and it doesn't seem to be throwing any more heat than usual.

Posted on: 18 March 2004 by Craig B

Hello Tibbs,

I appreciate your sharing your opinion - which, of course, I value highly.

BTW, I've been catching up on your 'New Speakers for Tibbs – The hard way!' thread this week and, I must say, it does appear that you have done quite the job there.

Congratulations all round and do enjoy re-discovering your music collection.

Craig

Posted on: 19 March 2004 by Mr.Tibbs

"Congratulations all round and do enjoy re-discovering your music collection."

Thanks Craig.

"does that mean my 1997 vintage 135s need to be recapped sooner rather than later? I do seem to detect a bit more grain in the music than I'm perhaps used to. Or am I being overly analytical of the E-IIIs again? Your counsel please."

The electrolytic reservoir caps go off quickest of all capacitors. They deteriorate slowly and steadily over their lifespan, the length of which depends on a few factors. They get a pretty rough time in a power amp or integrated amp, with all that current rushing in and out.

Lifespan before failure is hard to predict - they'll probably soldier on for 15 years or more, before spilling their guts inside the amp. Long before then, the amp will have gone off song, with increasingly poor performance at both ends of the audio spectrum. You could change the caps at 5 years and hear a worthwhile improvement, but if you can't DIY, best wait until about 8 or 9 years and get the amp fully serviced at the same time.

Regulated amps such as the 250 and 135 are probably less fussy about lower capacitor performance, as the regulators isolate the amp from its raw supply. The worst affected amps would probably be the NAIT’s, as their power supply is small and the demand comparatively large.

Mr Tibbs