What’s gone wrong with my amplifier?

Switched my hifi on last night.

Nasty background buzzing noise and the amplifier has lost load of volume.

So it’s still “working” but lost some power.

Any educated guess on what could of caused this?

It’s a s/h Naim Nait 5 which cost about £500 a few years ago, I guess any repair is going to cost at least £150 – £200, by the time it’s been shipped and diagnosed.

FWIW I’m going to open it up later and see if there’s any components that have obviously gone bang.

I have no electronics knowledge beyond VIR but do own a multi meter.

Wasp nest.

Sounds like it could be a supply rail has failed for some reason. Might be worth inspecting any big electrolytic (round metal can type things) for physical signed of failure as a first step. If you are careful you could try and check the supplies with your multimeter with it powered in to see if they are as expected.

@bigginge – How would I know what they should be? Is it voltage or power I should be looking at?

Probably a dumb question but you’ve checked the speaker cables haven’t been pulled loose or some other simple thing?

Yeah, I did the basic checks.

Took the DAC out of the system as well.

It worked perfectly the day before.

No idea what’s wrong with your amp, but I know where I’d send it! I had a problem with my Naim NAP 140 just this week, and John Jackson at JJS Thatcham did a same-day repair for a very reasonable price. If you give him a call on Monday morning I’m sure he’ll be able to advise.

@lorax     Thanks for that. I’ll ring him on Monday. If you don’t mind me asking, how much was reasonable?

I’m thinking of possibly replacing with something newer but not as high end.  Maybe a Rega Brio or Marantz PM6007.

Don’t want to spending hundreds on repairs only for another bit to go pop later.

The Nait 5 came with two versions of the volume pot, one is the “resister ladder” and one is the “alps” type, both have known issues.

Give darren a call at Class A servicing as he will be far cheaper than Naim and will have it back to you in working order quickly.

How does it sound though headphones?

It doesn’t have a headphone output.

Does it happen on all inputs or just some? That will at least tell you if it’s the pre or power section.

I checked with mr b for you who used to work in the test department at Naim. He says:

I suspect it’s gone D.C. best unplug speakers. If you can use a low voltage multimeter on -/+ of each speaker output, and it’s more than a few 100mV then switch it of and send to JJ with my recommendation (I worked with him at naim).

@Anna-B – what does “gone D.C.” mean?

Yes I had to check that too. Broken direct current, shouldn’t have any volts dc on the speaker output essentially. Milli volts ok, volts not. My interpretation of a diagram he just drew of what yours might be doing is the output is flatlining at volts, it should be wiggly up and down at milli volts. You can tell I didn’t work in the test department at Naim  😀 if the flatline scenario, potential to melt speak coils so unplug.

@Anna-B- Thanks for your and Mr B’s help but it’s not that.

I was getting a few milli volts across the speaker outputs.

I opened it up and there is nothing obviously damaged. There is very little inside TBH, a big power supply, 4 large caps and then a few IC’s. I was expecting a bit more for the cost of these things!

I’ll try it with some different speakers later.

Well it looks like there’s an issue with my 4 week old Q Acoustics 3050i speakers!

Just tried the amp with another pair of speakers and it appears fine.

Going to connect everything back up and see if the fault is still there.

WTAF! Everything is back to normal.

No idea what the issue was the other day.

I have no electronics knowledge beyond VIR but do own a multi meter.

I don’t know what’s up with the amp, but with this in mind I’d suggest exercising caution on poking around with probes.  There’s a risk of further damage either to the amps or yourself.  Even unplugged, a decent-sized capacitor can give you a sting.

@Cougar – Fully aware regarding capacitor.

Just did a voltage check on the speaker outputs as suggested above.

On the whole, it sounds a bit like “Dismantle it, then remantle it like it was” has fixed it

Daft question but, might be worth a check on the wires in the plug / wall socket.

Make sure everything is tight and no stray strands etc.

Could it be the volume knob (pot) got a bit scratchy from a bit of dust ingress or something, and a bit of twiddling cleared it up?

But I dont think that would make a buzz, it would just sound ‘crackely’ when adusting the volume…

It will have a link plug on the back with a bit of orange Flexi foil connecting the two plugs. Perhaps the link plugs were a bit dislodged or the Flexi has been damaged in the past. This carries signal and power (and I think signal ground?) between the pre and power amp stages.

@RichPenny It’s a Nait 5i, 2 it doesn’t have that link set up.

It looks like this.

Ah, definitely not that then.