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Old 27th December 2012, 08:58 AM   #71
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That's normal when trying to run on a bulb limiter. The power supply to the amp just falls flat to below its minimum operating voltage and weird non-amp noises result. It's not meant to deliver audio with the limiter in place.

Yes, it needs firing up without the bulb or fit a big one first if you have such, like a PAR 38 outdoor or pro lighting lamp etc. It will briefly thump with full power available, as it may have done originally, since there is no speaker relay. I have amps that thumped right from new back in the 1970s - It makes no odds and speakers can handle that no problem, assuming it's not scary loud.

230V in the USA, you say? Are you also using a step-up power suppy?
Keep a close watch on idle current and keep the volume low initially. Monitor temp of VAS and driver transistors, they may overheat now. There's no point starting without speakers (not NS10 ) fitted so fire away but hang on the switch too.
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Old 27th December 2012, 09:47 AM   #72
gilwe is offline gilwe  United States
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Regarding the QUADs - well, both the 303 and 405 are in my list of favorites (I have both). I actually like the 405 much better than the 303, although the 303 is a bit warmer sounding.
Just can't get the details with the 303 :/
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Old 27th December 2012, 12:51 PM   #73
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Yes, many have regrets about the aged sound of their 303s. Mine is still original (apparently). It needs a new broom to sweep out the old caps (expensive!) in there but the exterior is to remain original or it's worth very little. This is a great and somewhat technical site, if you haven't already seen it.
http://www.google.com.au/url?sa=t&rc...55325884,d.dGI
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Old 27th December 2012, 08:11 PM   #74
gilwe is offline gilwe  United States
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Hi Ian,

The NAP90 with the vintage Tannoy Mercury-S pair sounds amazing in my studio, even with these "replacement" trannies in the right channel I actually placed a similar Fairchild FJE13009-2 instead of the CDIL BD911 in it, hoping it will sound better, but it seems the change in sound is really more in the VAS variation. Also got the pair of BC239C in (Q1, Q2) after testing them to verify they're good. I will order a bunch of ZTX752/3 ZTX652/3 and genuine Fairchild BD743 to fit in it later. Really like this setup for close monitoring !

The 230v is coming directly from the outlet, I'm located in Europe

Last edited by gilwe; 27th December 2012 at 08:27 PM.
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Old 27th December 2012, 11:08 PM   #75
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That's great that you have it working again - good work! Are you still hearing high levels of buzzing in the repaired channel?

So being in Europe is the reason for all the UK gear - that figures.
Now I'm jealous to hear it for myself but that's your privilege.
Enjoy...
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Old 28th December 2012, 12:22 AM   #76
gilwe is offline gilwe  United States
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Thanks, and thanks for you great assistance, very much appreciated !

Yes, the buzz/hum is much lower now - the same level as on the"good" channel.

The channel still sounds less detailed and a bit "duller" than the "good" channel.

Curious to hear how it will sound with the original BD743 in it. Will probably take some while to arrive (from Hong Kong)

Really love this little amplifier !
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Old 28th December 2012, 01:37 AM   #77
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I don't think you'll notice anything, since the issue is about reliability more than audio quality but do
check if these look new - a good sign of fakes, which is the great fear of buying semis from China.
Yes, most people regularly buying there have been "stung" even if they don't realize it.
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Old 9th February 2013, 05:06 PM   #78
gilwe is offline gilwe  United States
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Hi again !

Just coming back to report that I also replaced the "replacement" transistors toady with genuine ZTX653 / 753 and the amp sounds superb ! (took a month to arrive...)

The use of BC640/639 did make the channel sound blurry and dull compared to using an all-ZTX set ! So this is to anyone considering replacing the ZTX trannies. The ZTX must be a part the NAIM sound after all
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Old 9th February 2013, 08:17 PM   #79
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Excellent. That's similar to what others have said about substitutes for the VAS transistors. 'Hope you get many hours enjoyment from it.
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Old 9th February 2013, 09:43 PM   #80
gilwe is offline gilwe  United States
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Thanks Ian, and also thanks for your help in the recovering process

Do you recommend replacing the Fairchild FJE13009-2 with BD911/BD743 just for reliability or should such swap also improve sound?
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