Fault on CB NAP250 - diagnoses welcomed

There is a chance that I left it outputting at 42 on the volume knob last night, after listening to music, with the SU pre amp muted. Would the NAP still be 'working' during that period, and might it therefore be a thermal protection circuit?

I think a NAP is a NAP in this instance. The only thing I can think of, as the 250 seems to be fine, is that either the din to XLR lead has a loose connection, or that you have inadvertently turned off the SU’s analog output, which would have required you to hit the spanner button on the remote, which I’d expect you’d remember. I’d undo the plugs on the interconnect and have a shufti. 

With the SU on mute the 250 isn’t working, so it shouldn’t be the thermal trip - the amp has to reach 70C for that to happen, if memory serves. 

Thanks, Mr Halibut. Yes that just occurred to me as being impossible. When I noticed the fault this morning, the NAP was blood-warm and no more, which is usual if it's not being used.

I was thinking it's an interconnect issue, maybe caused but unduly enthusiastic dusting by the cleaner.

I agree with HH. Check the interconnect connections look ok, especially the common or earth connection. Then I'd put it all back together, turn it on and see whether it now works.

it won't  be a thermal cutout from leaving it on overnight with the volume turned up if there was no music playing. My 272/250 DR is left on for months at a time with the volume wherever it happened to be when I stopped listening.

best

David

Hi HH, I'm not sure the SU's analogue output can be turned off via the menu. It's possible my fiancee did something amazing with the remote but unlikely. I just checked and the digital out of the SU is turned off and everything else is as I set it.

How might a lose connection between Din and XLR manifest - broken solder due to being old? What else might go wrong in a NAP.

Thank you, once more, for helping me to decipher this.

Donkeyhaute posted:

zesty gags

Knowing full well that I wasn't going to be able to help, I turned to your post in the more than expectant hope of exactly these.

Anyway I hope you can get the NAP sorted, and music back.

As it is affecting both channels, it is either the common connection at one end or the other of the interconnect or a power supply fault in the 250. But as it made a screech when you unplugged stuff in the wrong order, it sounds more like an interconnect problem.

Broken wires in an interconnect that isn't moved often is very unlikely. Solder joints don't age, but a badly made joint (dry joint) do fail eventually. More likely though is that there was some corrosion on the interconnect pins or the socket at one end or the other and plugging them in and unplugging each end a few times might sort it. Make sure the power is off though!

best

David

Just unscrew the two plugs and have a look inside. There is nothing to lose. 

If the NAP250 has been powered down a while, have you tried powering up again and seeing if it works OK.  It's odd for an interconnect fault to affect both channels, usually it's just one, however I don't know whether there's something about the i/c in question that may make such a fault more likely.  And yes, if you try unplugging a SNAIC or 4pin DIN to XLR lead while powered up and connected to speakers you will get an almighty screech through the system. You could try substituting the original DIN-XLR to see.

Otherwise, check the SU pre-out.  If no dice then it may be time for a service engineer to take a look. 

Donkeyhaute posted:

Hello everyone, I hope you're all booming with health.

I have a problem, and an SU, connected to a CB NAP 250, via Witchhat - and from there to Guru QM10 Mkiis.

It's gone swimmingly for years. The CB NAP 250 was serviced by Witchhat in 2013 with records to attest to the fact. It was bought from a forum member in 2014. 

This morning, no music was forthcoming. I had assumed the cleaner inadvertently hit the CB NAP's power button (whose light no longer works). I powered down and up. There was a thump from the speakers when the NAP was turned on again, but no music. 

No inputs from the SU could be heard through the NAP and speakers. Power cycling the NAP brought the expected thumps, but nothing played. I turned the SU off and on again, but still zip.

A bit panicked, I started mucking about with the interconnect without turning the NAP off and a dreadful screech came from the left Guru. I guess this indicates that something is emerging from the speaker ports of the NAP. Cursing myself, I unplugged everything, waited for a while, then took the NAP out of the frame. The NAP's fuse was intact.

I reactivated the SU's internal amp and it now plays completely normally via all inputs into the Gurus. No blown tweeters, thank God.

However, I'm at a loss for what could have gone wrong in the CB 250. Evidently some sort of current was still hitting the binding posts until I pulled it out of the rig.

I wonder whether any of you wise sages have experienced something similar and can explain it to me. What could have gone wrong with the NAP. Have i missed a stage of diagnosis? Where should I send it to be fixed, and how much might that cost?

Apologies for lack of zesty gags in this one. 

Full system in signature, but I need CB NAP experts, I fear.

Not the fuse in the power lead to the 250 is it?

Alley Cat posted

 

Not the fuse in the power lead to the 250 is it?

Hi Alley Cat. I don’t think a fuse in the power cable as the thumps and screeches still occurred. But I’ll take a look.

Richard Dane posted:

If the NAP250 has been powered down a while, have you tried powering up again and seeing if it works OK.  It's odd for an interconnect fault to affect both channels, usually it's just one, however I don't know whether there's something about the i/c in question that may make such a fault more likely.  And yes, if you try unplugging a SNAIC or 4pin DIN to XLR lead while powered up and connected to speakers you will get an almighty screech through the system. You could try substituting the original DIN-XLR to see.

Otherwise, check the SU pre-out.  If no dice then it may be time for a service engineer to take a look. 

Hi Richard, thanks for answering. And apologies for the reply with quote, I’m on the mobile. How might I check the SU pre-out? That’s a good point which fits the symptoms. Jack 

hungryhalibut posted:

Just unscrew the two plugs and have a look inside. There is nothing to lose. 

Hi HH, please can you elaborate a bit? Do I unscrew the interconnect fitting at the NAP end? What do I look for? Corrosion and broken bits? Thanks for helping. 

David Hendon posted:

As it is affecting both channels, it is either the common connection at one end or the other of the interconnect or a power supply fault in the 250. But as it made a screech when you unplugged stuff in the wrong order, it sounds more like an interconnect fault.

best

David

Hi David, thanks for your kind reply. The cleaner had been told not to clean the Hi-Fi, but I’m interested to learn how a power supply fault might be the culprit. This sounds expensive. If the power supply IS broken, how do we account for the normal thumping and the screeches I stupidly induced? 

Thanks again, 

Beverley Steamed Pilchard

I don't think it is the power supply in the 250 as I said in my post, for the reason you give. I reckon it's a poor contact in the interconnect earth/common connection. But it could be an SU fault as Richard says, but very unlikely I think.

best

David

Thank you David. Sexually outraged cat now prime suspect in punctured interconnect. Good news if it is the WitchHat. I’ll reconnect later this evening and test. 

I once had a strange fault in a satellite tv set top box which took the house electrics out too. It eventually turned out that one of my cats had been sick into the ventilation slots on the top of the unit and the set top box was toast. After quarter of an hour of checking things,  unplugging it meant the house supply would at last stay on. At least Naim doesn't put ventilation slots in the top of their boxes!

best

David

I’m looking forward to my domestic supply vomiting onto the cat for karma’s sake.

Good to have you back Donkeyhaute, although I accept the circumstance could be better. 

Hope you get the punctured WitchHat sorted, and possibly some counselling for your cat.

Apparently the static electricity from 23 domestic cats provide sufficient energy to start a car. If this fails to reinvigorate my NAP, I intend to find out exactly how many cats 23 electric hire cars can run over during a standard lease period. 

Talking about static electricity....

I found out that my vintage QUAD ESL-63s, when left on for days, can trip my Olive 250. It manifests itself by one or two channels muting. A quick re-set sorts things out.

What sort of speakers are you running your CB 250 into?

Hi Adam, I'm very thankful for your reply, and to all stout-hearted forum members who have selflessly pitched in to help.

The NAP is feeding Guru QM10 MkIIs, an easy load, via Tellurium Q Black. I've just returned from work, and the NAP is resting, as French women are wont to rest (via Titanic), upon my sofa.

I'll reconnect after supper to see what's occurring. I don't think load is an issue with these speakers.

But I've always lusted after a pair of Quad Electrostatics. Perhaps Leonardo could expunge his crayon upon them.

UPDATE. I've returned to my home. My bosom bursting with your collective wisdom. 

I plumbed the NAP250 back in. Some judicious shaking of the WitchHat interconnect occurred.

I switched the SU from internal amp to external.

I turned on the NAP in the correct order this time.

No sound.

As a last resort, I turned the SU's internal amp onto 'All outputs' (I'm not sure what this means), rather than 'internal' or 'external'.  Now there's sound.

I'm only a minute into a familiar track but it sounds ok. 

What does 'all outputs' do. And what has failed on the SU? Or is the cable still in play?

DE PROFUNDIS CLAMO AD TE DOMINE.

PS: is it time for a 272?

How do I edit this thread to exculpate the innocent 1984 NAP 250?