My warm CB 250

I have a 1984 vintage NAP 250 that was serviced by Naim in August 2019. This now runs permanently on the high side of “warm” and gets towards “hot” during a session.

A couple of months ago I switched from using 6 meters of A4 to 3.5 meters of A5 so could this be the problem?

As far as I can remember it was always cool to touch when on standby, but I reused the SA-8’s so changing back isn’t easy.

Does anyone know if it was always normal for the CB 250 to be very warm when switched on but not in use or do I have a problem somewhere?

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3.5m of A5 per channel is the minimum but it may be down to some issue somewhere. You say you re-used the SA8s. This can create issues, especially if you mixed solders - i.e. it had leaded solder and you reused them with lead-free. If it were me I would bite the bullet and get some new SA8s and re-do the soldering.

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I have a CB 250 - which was ‘re-shelled’ by Salisbury, as Olive. It can get a bit warm, but I think that’s normal for a 250…

Mine drives via 8 metres of NAC-A4.
Believe trials done by Naim suggest that in this case, longer is better… :astonished:

PS. The design of the Naim 250, being a regulated amp, means there are really 4 amplifiers inside, not just the expected 2. So more potential to generate heat.

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Hi AJK

Mine runs reasonably warm but never hot these days

I do remember though in the 1980’s when we were all young many parties were the order of the day (and night) :grinning:

My 250 of the day then ( and my mates 250’s ) use to get so hot here in Sydney in summer they would just cut out completely , which was not a good look at the height of a party ha ha

Do you run yours for quite a long time for your sessions?

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Thanks Richard. They were put on by the dealer as I am only just about competent enough to plug them in.

Do you think 3.5 meters of A5 is enough on an early model?

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I can get to listen for 4 hours + at the weekend.

Of course its the “standby” temperature I was worried about.

I don’t think you have a problem, here… :thinking:

3.5m should be enough as otherwise it would not be recommended as a minimum. However, my own preference is for 5m+ per channel. I think the Naim amps sound more “at ease” with that length.

As for the NAP250 getting hot, we are entering summer and so ambient temperatures will have an effect on the ability of the casework to cool the amp. Is it kept in a confined space, or is there plenty of airflow around it? Is it just the cable length that has changed or have you moved the system or changed anything else?

Only change was the speaker cable but I can’t be sure it didn’t stay “warm” before I noticed it. It has a Hicap on top and is on a wooden panel straight onto the floor, so limited air-flow.

It sounds like I need to give it some more space and try and get over it.

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I think I read somewhere on the forum that you could also get away with switching a CB NAP 250 off between sessions as it warms up quickly. Maybe switching on Friday night for the weekend.

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Shouldn’t get too hot on standby AJK

But yes need more airflow around required maybe and no stacking

What an absolute iconic product the CB250 is in the history of audio products over the last 40 odd years +

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It was an aspirational product for me as a teenager in the 1970’s and to get one was a dream come true.

Fact it sounds as good as ever after almost 40 years is miraculous. And a bargain too!

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That’s what I do. Everything else stays on, but the 250 goes on when I play something.

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Thanks for the help everyone

I moved the Hicap and found some thick, arty coasters in the kitchen to give the 250 some air flow underneath. It has cooled down to “normal” tonight, and so have I.

Now to go and warm the 250 up again in the way JV intended!

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According to the epistles, JV put the amp on a side and a fan next to it for the airflow.

Forget racks, you can greatly reduce the hifi footprint by this setup.

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And put the amp in a cupboard when it hums… :stuck_out_tongue_winking_eye:

Obviously that might create airflow issues. But who argues The Book isn’t full of contradictions… :sunglasses:

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