NAP150 Options?

[Suffolk Tony]

Hi folks,
My old NAP150, which by my reckoning's over twenty-five years' old, is overdue an overhaul. It currently resides in my surround sound system, driving a set of ceiling speakers, and from what I can tell still sounds OK.

Anyway, I peeked inside it today, and the caps appear to be intact. Now I'm deciding what to do. I could just replace the caps and the tants (is there something better to use rather than the latter?) but I also happen to have a couple of "NCC200" Chinese copy boards, which I populated, replaced all the transistors with UK-sourced ones, and they work OK. I've also got a few of the generic rectifier/cap boards, so I'm wondering if I could remove the one-piece NAP board, fit the NCCs & rectifier boards, & just use the transformer?

Not sure about what values to use for the caps on the boards...Anyway, any help and advice, as usual, most welcome and appreciated.

 

[neiljadman]

As it happens I only recently acquired a NAP 150/NAC 112 pair - listed as non working and in mint condition with original cartons...a bargain price too. The only faults I could find on either piece were a leaking reservoir cap and a dead LM317. Once both were replaced normal operation was resumed and the 112 proved to be working anyway.

Based on this recent experience and the experience of seeing similar failures of these caps in other Naim power amps, I'd highly recommend replace all of the reservoir caps since the faulty ones tend to leak acid on to the board - neatly out of sight underneath the cap with nothing to see from above.

At the same time I decided to do a total recap of the amp, replacing all of those old electrolytics. Wima MKS2s in the input coupling position, a 68uF tants on feedback and bypass duty and 10uF tans in the SOA - which I left in place since I intend to re-sell it, otherwise that would be out too. I was pleasantly surprised - it's a good sounding amp.

 

[Gervais Cote]

Hmmmm........
Personally, I wouldn’t make any major modifications on such a nice amplifier.
I would replace the tantalum for the same as original, electrolytic with high quality Nichicon or equivalent and if you want the best of the best for the reservoir capacitors, go with Mundorf M-Lytic.
Also have a look at the large resistors near the output transistors and if they don’t show any traces of heat, just leave them there.
Best way to upgrade those Naim amps is to hook them to a better preamp IMO.

 

[Suffolk Tony]

Thanks folks. I do agree, on the odd time I wire this into a stereo system (usually when I manage to blow up my dual-mono DIY Voyager) I'm always surprised by how good it sounds. Think I'll take your advice there Gervais, but I'll skip on the Mundorfs! What are the values of the tantalums please? Can't read them at the moment.

 

[misterc6]

The only tantalums I can see are the two blue ones in the 24v regulator circuit on the left-hand edge of the board, they're almost certainly 10 uF, 35 V.