Curioser and curioser.
What have I got here?
I appear to have the heatsink with the recesses but still the 250-2 shape?
Yes it would be nice if anyone from Naim or Richard recognises this configuration. Comparing the pictures the underside of the heat sink appears to have the 009ās.
All connected up and is working well. I am going to have to get used to the sound and then swap back to the 250-2 to compare. It seems to be have a little more bass at low levels but that could just be me and buyer expectation.
I wonder if itās a NAP250.2 upgraded to DR spec? Or maybe a transitional model? Iām no expert here on the later classic kit so probably best for @NeilS to comment.
1 Like
Thanks Richard. It was sold as a 2016 250-2 upgraded to 250DR in 2018. Unfortunately Naim say they have no record of that. I do have a copy of the dealer invoice to the person I bought it from but no serial number is recorded on that invoice. I will contact the dealer at some stage but before doing so I wanted to have an idea of what I have- DR or not.
A question to you Richard. Were Naim dealers allowed to offer their own DR upgrade service at any time?
Edit 2014 250-2 and 2019 DR upgrade. ( Just checked the invoice)
1 Like
I donāt think so, but it was after my time at Naim so couldnāt say for sure. I do know that some distributors did DR upgrades, and some of them went a bit āoff pisteā at times, so there are one or two bits of āDRedā Olive kit around.
Interesting you confirm itās an upgraded unit, I guess perhaps the original heatsinks are drilled and reused? Again, Iām sure @NeilS can enlighten on the process.
2 Likes
The entire PCB/heatsink assemblies were replaced during a DR upgrade.
@bruss your heatsinks are the correct DR ones, Iām unfamiliar with the āfullā versions in the pictures above, perhaps those pics were of a pre-production unit.
If Iāve picked out the serial number correctly, your unit was updated @ Naim in Aug 2019 & the power switch was replaced at the same time.
Regards
Neil.
4 Likes
Woo-hoo - resultā¦!!! 
If I have read the Serial No right (starting 37xxxx - ?), it shows that it was a 2014 build.
1 Like
Thanks Neil. That is really helpful. Unfortunately the service department had missed this when I enquired recently. A big relief. I owe you my thanks and a drink if our paths ever cross.
Yes it was my memory error above. My recent communications with Naim service department carried the correct number.
1 Like
Brilliant, thanks for clarifying @NeilS I guess the ones shown in the official pictures were the pre-production ones?
1 Like
I find it hard to believe that the 250DR etc have a 1000VA transformer. the Mark Levinson No. 23.5 although Dual Mono had 1258VA transformersā¦ 200 wpc at 8ohms 400 into 4ohm ā¦ Iād think a 250DR has maybe a 400VA or 500VA transformer. but Iām probably wrong 
Also looks like the top most picture that that amp is using MOS-FET out put devices?
Not MOSFETs but bipolars. They were originally BDY58s on the original NAP250 from '75, then Naimās own custom made NA001s from 1982. The final olive NAP250 used NA001s with the new NA007s in the regulation circuits.
The earliest NAP250 used a transformer rated at 400VA, then upgraded to one rated at 500VA in 1984 (I note the last Olives had transformers rated at 600VA - see the Thegreatrobertos image above). The NAP250.2 and NAP300 used a much bigger transformer that was rated at 1020VA.
2 Likes
Thank You Richard. 1000VA is a big transformer! Very much over-sized, but great for longevity and reliability. Good engineering.
So, the Transformer has got much bigger - but the Capacitors have got smallerā¦?
(well, they look smaller on the 250.2 onwards)
So, my 250 has a 500VA Transformer and NA001 Transistors - its from 1985.
Physically smaller, yes, but you get twice the number.
Yes, my CB 250 is also from '85 with a 500VA H&F transformer and NA001 transistors used for both the output and regulation.
1 Like
Thatās all I can imagine, I havenāt seen that style of heatsink in the flesh. Seems odd that the cutout would be omitted, as it was present in the non DR version. Obviously the cutout provides clearance for the Ch.2 speaker sockets/wires.
Regards
Neil.
1 Like
This topic was automatically closed 60 days after the last reply. New replies are no longer allowed.