Nac 72 140 not working on one chanel

Just bought these second hand today. As above only working on onw chanel. Has something blown on the 140? If I switch the speaker conections over it doesn’t work on the other speaker…so I guess they’re ok.



Power off the kit.
Remove the lid on the 72 but pull the innards forward so not to damage fascia.
Reseat the internal boards and try again.
Also check the 72 to 140 cable SNAIC with a Multimeter pin to pin to see if there is a break.

If the reseating doesn’t work try swapping the gain cards (321) and the time aligned boards (729) over - as in swap the left channel with the right. Done set at a time and then test. Doubtful that a board has gone but you never know.

Did you try a different input?

Also, with power off and disconnected, try re-seating the link plug on the NAC72.

Ill try all those things at work today…Im an electronics technican. Some of the guys in my dept will have a much better working knowledge of thrse things to me. Im pretty sure its just on the one chanel. Its the same using a different input/source. Maybe one of the big caps has totally dried out?


You say you have ruled out the speakers, but have you ruled out the speaker cables and their interconnects also?

I think so Ravvie

I tried swapping the speaker cables over and it followed the LH chanel.


Thinking out loud here, if you reverse the Snaic (I know, I know it is directional …) if the Snaic is at fault the not working chanel should flip over to the other one?

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Could I use my old nait 3 as a pre amp to power the 140 to rule out the 72?


If you swapped at the 140 end of the cables then fine.

But if you swapped at the speaker end then the cables and connections can’t be ruled out.

Yep swapped at the 140 end.

So it is the 140 and not the 72?

For me, it makes more sense it being the 140. But who knows I need to have a really good look at it tonight.

So had a good look at things tonight, made sure all the boards were seated properly in the 72, put the case back on, plugged in and…nothing. the power amp didnt even come on. Checked the plug and thats ok. I can only imagine that somthing has gone in the 140?

Made a note of the plug in boards. They are
X2 729/1
X2 321/5
X2 324/7
X1 325/7

Not sure if Im missing a crucial set of boards? I’d settle for that st the moment!



I[quote=“Ardbeg10y, post:8, topic:9755, full:true”]
Thinking out loud here, if you reverse the Snaic (I know, I know it is directional …) if the Snaic is at fault the not working chanel should flip over to the other one?

don’t think so. The pins will still go 1-1, 2-2 etc.

I’d certainly want to check out the SNAIC with a meter for continuity.

Hi Stephen

Yes that was one of the 1st things I did. Checks out fine.

Is there a way of checking the voltage further upstream in the 140? I have a feeling it is not being powered. I checked the power cable and that was reading 235 v.

Would it be worth removing the heatshrink from around the internal socket to see if there’s anything funky going on there?



In terms of not working, is there any hiss listening close by the tweeter? (With input to the 140 disconnected) If yes then if problem is the 140 then likely to be input end. If no then either power supply or output stage of the 140.

If comfortable working live, I’d power up open, and check voltages at different points, simply looking for differences between channels, guided by above. If there is hiss, I’d try get a non shielded insulated long wire with one end insulated and the other bare and lie it alongside mains wires and touch the bared end at points on the signal path (or anywhere if unsure) listening for hum or just any sort of noise as you touch it, comparing between same on different channels. That may help track down what part of the amp.

Thanks IB

At which points in the 140 can you try the voltage please?


I’m very concerned about anybody poking around inside a live bit of kit. DIY discussion is not permitted, as you know from reading the forum rules. You should get it checked out by a Naim dealer, Naim service or someone like Darran at Class A.

Fair enough Richard.

Having just spent 470 on what is in in affect a paper weight, the prospect of spendind another 300 is one that I don’t find appealing.