NAD 2200 mods and upgrades

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I have been recapping and modding NAD 2200s for a while now- and wanted to give some details back to the community:

I have selected a number of mods from AK and DIY Audio and others listings, as well as my own tests, and these seem to make the majority of difference:

C215-218- These support the 18v rails that provide the power to the initial VAS stage of the power amplifier broads, and as such larger values provide a greater local reservoir. Replacing the original 2.2uf 50v with 470uf 50v makes quite a difference, “more bass” and better dynamics, I have settled on Nichicon HE (ultra low impedance)
C111-114- I have replaced these with COG Ceramics and have added 47uf 50v in parallel with each of these (across the 18v supply lines to the IC) and this again seemed to provide better dynamics, these are Nichicon PW
I tried Pilots (posted in AK) swapping of C109, C110 to 2.2uf 50v Wima- but ended up going back to Nichicon FG 10uf 50v- which gave more solid square wave response at frequencies below 100Hz
C107,C108- these were 820pf ceramics (circuit states 1000pf film)- so replaced these with WIMA 820pf 50v film
C203, C204- I tried a few versions (2.2uf Film, 10uf Film- both WIMA, Nichicon KL, Nichicon FG) and finally settled on ELNA SIMLIC II 10uf 50v- for me this kept the detail and was smoothest- also kept the LF square wave tidy.

I have also replaced a couple of ceramics with WIMA film on the main power amp boards

I replaced the 2043DD IC’s with LM4562NA- I had tried the OPA2134 (which is an IC I like), but again for me the LM4562NA is better suited to the amp-perhaps as it is BJT as is the 2043DD

All the other electrolytic capacitors have been replaced as follows:

Power supply- Nichicon PW same values
Power amp- all PW except c223, C224, C311, C312, C313,C314- all FG and C203,C204- ELNA Simlic II as mentioned
input amp- C109,C110 FG, C115,C116 Nichicon KA
plus the 47uf mentioned above across the 18v supply lines
10000uf 80v with Nichicon or equivalent
the 10000uf 120v are unobtainable, and the 160V versions are both expensive and dont fit- so I now have settled on Nippon Chemicon 10,000uf 100v (125v surge) replacements, which given that the high power rails are 95v, work very well indeed.  These have been operational for over 12 months with no problems.

for me this is the best NAD mod yet- more bass, better dynamics and measures well, though there is some low frequency phase shift and roll off from about 50hz downwards-the LAB inputs less so as expected.

one thought is to bypass the 10k ufs with a film cap (1uf?)- but again I have not tried this as yet.

Pioneer SX 850

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I have just started working on a defunct Pioneer SX 850. When it arrived there was no audio and no relay “click”. The insides, besides being dusty looked OK.

So I started with the power supply and removed and replaced all the electrolytic capacitors with a mix of Nichicon low impedance and audio types (all 105c). There are two transistors which should also always be replaced as they are often prone to failure. Having done this and with unit connected to a variable power supply with a fats trip and current meter, I turned it on, and still now relay click. So I tested all the voltages across the Power supply, ans everything is now as it should be.

So the next board to work on is the protection circuit, again there are two transistors, that should be upgraded, and all the electrolytics replaced. There are two small electrolytics, Sanyo, that I replace with WIMA film caps. Again turned it on, and hey presto the pleasant sound of the relay kicking in, so I then ran some tones through the aux input and all is good. Next is the phono equalizer, where all the transistors are replaced with low noise types and the small value electrolytics by WIMA film capacitors and the other electrolytics with Nichicon Audio types.

 

so fa so good- now on to the main amp boards- photos to follow

 

NAD 2100 upgrades

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so I have two NAD 2100s in for upgrade, one had a cracked PCB and is now up and working, all with new electrolytic capacitors throughout- The Panasonic 10k uf 80v from Digikey drop right in perfectly.

However the second NAD is being somewhat recalcitrant and I have pulled out nearly all the driver and and output transistors to try and find the problem. The issue is with the High Voltage rails,

and now I have it coming out of protection, which led me to look into transistor equivalents and replacements. Although the main outputs (Sanken) are also avialable from Digikey, some others, such as the 2SB922

appear to be unobtainable, and have very few appropriate substitutes.