Naim Nap140 problems

I own a Naim Nac62 and Nap140 which I bought in the mid 80s. I used them continuously up until about 10 years ago, then put them in storage until 6 months ago when I set them back up again. They’ve worked fine up until a few weeks ago when the fuse in the power amp blew on switching it on.

Given that the amps are way over 30 years old, I decided to have a look inside, I quickly discovered that one diode in one of the rectifier bridges was short circuited. I’ve bought the exact same part, but I’m wondering what caused it to fail? Old age, or are the capacitors in the power supply circuitry on their way out?

One thing that puzzles me is that since I set up the amps again 6 months ago, when I switched the amps on, there was a thud in the speakers, but I can’t remember if the amps always made a thud on switching on? Is it normal for the amps to make a dull thud in the speakers when switching on? And if not, is this a sign of failing capacitors?

Many thanks in advance

The thud is normal

An unserviced amp of that age is well overdue a recap. DIY is outside the scope of this forum, but you should deal with this before you use the amp if you don’t want to risk more expensive damage to your speaker drivers.

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Do you not leave it on 24/7? Repeated turning on/off stresses components more I believe.

Anyway, if it were me and I lived near Sheffield I would take it that well regarded Naim service centre for some much overdue tlc. If not, get a Naim dealer to get it back to HQ for same.

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Just get it serviced. Simple as that. Any issues will be dealt with a good service. Darran at Class A is very reasonable.

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Thank you all for your replies. Svetty says the ‘thud’ is normal, but ChrisSU says I’m risking more damage to my speaker drivers, I take that to mean that the thud causes damage?

I expect the diode failed through over curernt. I.e something downstream ( most likely the cap) has done short and allowed the excess current draw. Shame the fuse didnt provide protection. Anyway, time for some Class A action. And then another 30 years of fun.

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The thud getting louder is a sign that the amp needs attention, but the worst case scenario is that the output dumps DC current into the speaker and cooks the drivers, which can be much more expensive to replace than the caps in a power amp.

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So this Naim combo is 30 + years old, has not been serviced (ever) - ?

Just get in serviced. Discussing DIY fixes will get this thread nixed.

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As others have pointed out, electronic DIY discussion falls outside of forum AUP. If the NAP140 has never been serviced then it’s way past due. Note that a proper Naim approved service is more than just a “re-cap” and will have the amp back to performing as new again.

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10 years is recommended service requirement as we all know on CB and olive kit! :sunglasses:

No it’s not.

When I took my HiCap and 180 to Darran at Class A, he didn’t service the 180 as the caps were good for 20 years. There’s no blanket 10 year rule.

That’s Naim’s recommended service interval for Olive and CB equipment. 12 to 15 years for black boxes.

If the equipment is all good for 20 years after Darran’s say so that is fantastic.

I stand corrected if that’s the case.

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