Warning: extremely niche-audience post ahead.
I’ve recently had the opportiunity to perform a service and calibration on an original Naim NAIT integrated amplifier (new capacitors and bias adjustment). Fortunately I have also been able to look inside an identical model that had a dealer service and recap in 2018, so I could see what was used then.
I based my service component choices off of the dealer-serviced model and also off of the incredibly detailed post on Hi-Fi AF about recapping the very similar NAIT 2 (1988). Since no such parts list was easily findable for the original NAIT (1983) I’m posting this here.
If you’re doing this work, feel free to follow the Hi-Fi AF post regarding the NAIT 2 — these amps are extremely similar to work on, and the original one if anything is a bit simpler to take apart. There’s only one version of the original NAIT — it always has a built-in MM phono section.
This is essentially just a parts list and assumes you know what you’re doing in recapping a vintage amplifier. If you don’t, I suggest starting out on something less valuable (or in any case follow the basic guidelines around desoldering, soldering, and mains voltage precautions that I laid out in my post about the Linn Lingo).
Below are the parts I found in the dealer-recapped NAIT, along with notes about what I used for these components, and what I found as original parts.
- 2x Kemet 10000uF 40V “snap-in” style large cans. ALC20A series. This series can be tracked down but was not readily available to me; I used the very similar ALC10A parts as recommended by Hi-Fi AF. (The original 1980s parts were 6800uF cans.)
- The phono section had 7x Sic-Safco Promisic C031 47uF 40V axial gold-case capacitors. These appear to be obsolete and are rare and expensive to obtain. I suspect that these were actually the original caps that had been left in place on purpose during the service. (That said, the other un-recapped NAIT used some generic Elnas for these parts, so who knows.) I used Vishay 47uF 63V axials (MAL203138479E3) for these. But real talk, is anyone actually going to use the NAIT’s phono input at this point anyway? You might like the sound of the amp itself but surely you have a better phono stage.
- The preamp section has 1x Vishay 3300uF 40V 021 series axial part. These are easily obtainable, though I suspect any old 3300uF 40V+ axial part that fits in there will do fine. The original amp board used an Elna for this.
- The preamp section also has 4x Samwha RS-series 47uF 35V 105° radials. These replaced charming little Rodersteins in the original. Samwhas are a sort of surprising supplier choice here; they’re nothing special. These were the only high-temperature parts and it’s likely that’s just because they had those at hand. I can’t get Samwha parts easily and I don’t think they’re special anyway. I used audio series Nichicons here.
- There are many 10uF capacitors all over the board. These were 14x Samwha LL-series 10uF 35V radial parts. The LL series is “low leakage” and the datasheet for these does indicate great relative specs on that. I’m not an engineer let alone an amp designer so I can’t comment on whether that was a deliberate replacement choice by Naim HQ or whether these were just the parts at hand. These replaced, again, just some general purpose Elnas. And again, I used nice audio series Nichicons.
- Finally, the power amp section has 2x tantalum Kemet 47uF 6.3V radial parts. I didn’t replace these because they don’t fail like electolytics do (although when they do fail, they can fail short, which can put the rest of the circuit at risk… maybe I actually should go do those!).
It’s a pretty simple recap job. As noted in the Hi-Fi AF post, be careful with the mica insulators that sit between the transistors and the heat sink — you want to make sure you retain the originals (and place them carefully) or use fresh ones (very cheap from Mouser, etc) when you put the heat sink back together.
While you’ve got the amp open, I’d recommend working a generous amount of Deoxit as best you can into the bodies of the pushbutton switches, especially the power switch. The electric arcing of mains current from turning the amp on and off will eventually build up carbon inside the switch and you’ll get crackling sounds in the speakers from it. At some point you may need to replace the switch (original is an obsolete Alps 2PDT part).
Calibrate the bias current as in the Hi-Fi AF post. And you should be good to go for another 40 years!
Among other things, I service and restore vintage audio, computing, and household electronics. You can see some of it at hayesvalleyhardware on Instagram. Feel free to get in touch at bzotto at Gmail if you have something old you want help with.
