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2SD786/ 2SB737's + film capacitors

Discussion in 'd.i.y.' started by Richard Lines, Oct 8, 2019.

  1. Richard Lines

    Richard Lines pfm Member

    Good Evening,

    I have done a search and it is some time since the subject of these replacement transistors for the MC boards in Naim pre-amplifiers was a forum thread, it's a bit like the previous threads for group buys of film capacitors for modifying Naim amplifiers as well.

    I see the passage of time hasn't made sourcing any of these parts any easier.

    My first question has to be are there any members out there who acquired parts for carrying out modifications previously who just never got around to it or whatever who might be inclined to consider selling any parts they may have?

    My second question has to be are there any members who might be interested in a new group type purchase? I'm not committing myself to co-ordinating anything at this point just gauging interest. I've already determined none of the parts are going to be easy to source.


  2. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Fairly pointless I would have thought... those Rohm transistors are very quiet but the paralleling of the input transistors in the Naim MC board should make them quiet enough anyway...
    If anyone really can't stand the hissyness there are vastly more obtainable parts which, whilst not as quiet, are significantly quieter than the standard ones.
    I have a few 2SB737 but probably only 6 or so and I'm "saving them for a rainy day" as it were!
  3. chiily

    chiily PFM Special Builder

    Years ago I modded a pair of MC323 cards, this is a summary of the work I did:

    A quick run down of the mods to the MC cards.

    Removed the crude on board regulator and replace with a pair of ALWSRs.

    Replaced all the ZTX384 transistors with 2SD786, especially those in the low noise ladder. Beware the change to pin outs!

    Replaced the 15R current balancing resistors in the ladder with Vishay/Dale RN50Cs.

    Replaced the 47uF feedback capacitor with a 47uF film

    Replaced the power rail cap with a Sanyo 47uF OSCON SP. Now removed with the ALWSRs close by.

    Replaced the i/p and o/p decoupling tant caps with BC128, solid Alu caps.

    Replaced the 6.8nF and 22nF caps with polystyrene equivalents.

    As I couldn't lay my hands on a 68nF ploystyrene cap (at a reasonable price!) I use a Polyphenylene Sulphide (PPS) one instead.

    And various resistors for RC55Y equivalents.

    A couple of resistor splitting mods a la Les W

    [​IMG]2008_03150323 by Garf Arf, on Flickr

    I'll post some pictures when I get home.

    I too have a stash of 2SD786s and 2SB737s. I bought them years ago for pennies. They sell for a bomb on ebay these days.

    In fact I don't use the cards anymore. No idea what they are worth, but the 2SD786 are worth a few quid each. :)
    Last edited: Oct 10, 2019
  4. Richard Lines

    Richard Lines pfm Member


    2SD786 available at $1.25 each from njsemi.com - just needs a bulk buy.


  5. Richard Lines

    Richard Lines pfm Member

    Good Evening All,

    I see the BC128 series of solid aluminium capacitors are now unobtanium. Vishay took them over and the 128 series are no more. I can see that this is going to be frustrating......

    Addition - Altered the way I searched on eBay and found these - https://www.ebay.co.uk/itm/4-conden...0ac54:g:OlwAAMXQsmFRblAO&shqty=3&isGTR=1#shId - bought all three lots.........

    Evox have been absorbed by Kemet. Elfa in Sweden are doing a special offer on the Kemet SMR 2.2uF/ 63V capacitor currently at https://www.elfa.se/en/radial-film-...mr15225j63b12l16-5cbulk/p/30033277?track=true for only SEK 21.58 or about £1.80 which seems a bargain but would need a largish order to offset postage.


    Last edited: Oct 11, 2019
  6. Richard Lines

    Richard Lines pfm Member

    Good Morning,

    The market has clearly moved on in the last 15years and it isn't entirely clear why the the Evox SMR devices were the 'device of choice' - was it entirely its sonic ability or availability of suitable parts? There are a number of 47uF/ 50+VDC film capacitors available now (best price for one quoted):-

    1. Kemet 47uF/ 63VDC (R60 Series) - R60DR54705050K - DigiKey - 399-12459-ND - £7.92
    2. Kemet 47uF/ 100VDC (R60 Series) - R60ER54705040K - Mouser - 80-60ER54705040K - £8.76
    3. Epcos 47uF/ 63VDC (B32524 Series) - B32524R0476K000 - DigiKey - B32524R0476K000-ND - £9.90
    4. Epcos 47uf/ 100VDC (BC32524 Series) - B32524Q1476K000 - Farnell - 2468902 - £11.11
    5. Epcos 47uF/ 100VDC (MKT Series) - B32526T1476K000 - Mouser - 871-B32526T1476K000 - £12.61
    6. Epcos 47uF/ 100VDC (B32526 Series) - B32526T1476K000 - Farnell - 2797797 - £15.77
    7. Wima 47uf/ 50V (MKS 4 Series) - MKS4B054706F00KSSD - Mouser - 505-MKS4B054706F00KS - £8.64
    8. AVX 47uF/ 100V (FFB Series) - FFB44E0476K-- - Mouser - 581-FFB44E0476K - £13.42

    The No. 8 Wima device is relatively new and is less than half the size (volumetrically) of No.1

    Previously recommended Vishay MKT1826 capacitors are also now unobtanium but there is a supply of the 3.3uF versions available on eBay at https://www.ebay.co.uk/itm/MKT1826-...209619?hash=item4699a18313:g:WygAAOSwLmhdLHZe but be aware they are Swiss based so EC members will need to look out for import duties.


    Last edited: Oct 11, 2019
  7. Richard Lines

    Richard Lines pfm Member

    Good Evening All,

    As I move down the acoustica guides to modifying the pre-amplifier/ components I see the 3.0uF Multicap RTX are only $69.40 each (circa £55) at Parts Connexion. 2off + tracked postage + the Royal Mail £8 admin charge and VAT would make a pair of these a whopping £186..... I think these will remain nice to have at least until cheaper changes have proved their worth.


  8. Richard Lines

    Richard Lines pfm Member

    Good Afternoon All,

    There doesn't seem to be a great deal of interest in modifying Naim input boards then????

    Having nothing else much to do I've now narrowed down my choice of components simply, for the most part, based on price:-

    1. Wima 47uF/ 50V (MKS4B054706F00KSSD) - Mouser @ £8.64 - there is a cheaper Kemet 47uF/ 63VDC (R60 Series) at DigiKey for £7.92 but this Wima is less than half the size....
    2. Wima 10uF/ 63VDC (MKS4C051005F00KSSD) - Mouser @ £2.86
    3. Polystyrenenes - all LCR series from Farnell - 6n8 @ £2.28, 22nF @ £2.81 & 33nF (x2 to make almost 68nF) @ £3.74 each
    4. 47uF/ 35V Nichicon NHG - DigiKey cheapest @ £0.22 but as it would be the only thing I'd be ordering from them I'll go with Farnell @ £0.28

    I've ordered some of the 56uF OSCON SP capacitors from eBay.

    I think that's the parts sorted........ addition - maybe not I've just located some original Elna Silmic 47uF/ 63V rated (I see there is a great profusion of Silmic II capacitors floating around!!!) - https://www.ebay.co.uk/itm/ELNA-SIL...228389?hash=item261a410e65:g:JPwAAOSw0i5agZ4m - the seller can't be a million miles away from me......

    Further edit - still trawling eBay and looking for unobtanium large capacity MMK's and found 22uF/ 250V MMK at https://www.ebay.co.uk/itm/2-pcs-MM...288239&hash=item3a869dd8bc:g:IzoAAOxyDEVSbOw1 - OK so they're going to need connecting in parallel and 44uF is close enough to 47uF.......


    Last edited: Oct 12, 2019
  9. timH

    timH Senior Moment Member

    Hi. I’ve got a couple of the 3.0uF RTX that you can have for way less than pcx. Send me a message if you’re interested
  10. Richard Lines

    Richard Lines pfm Member

    Tim - PM sent

    As I continue to look at options the best price I can find for the Mundorf MCap 5.6uF/ 250V capacitors as mentioned in the acoustica.org information is at - https://www.ebay.co.uk/itm/1-pair-2...var=460209631693&_trksid=p2060353.m1438.l2649. They are marginally cheaper than one French supplier I found (who wanted an outrageous €10 to post 4 capacitors to the UK and that's before Brexit.....)

    I have sent an EM to Elfa in Sweden asking what the minimum number of these discounted Kemet 2.2uF/ 63V SMR capacitors would qualify for 'free' shipping. Within Sweden it would appear to be 26 items. There might be a Swedish based pfm member who could act as a postal intermediary?

    There is a Hong Kong based (yes I know there is a 'risk') eBay supplier of 10uF/ 35V Elna Silmic capacitors - the picture does show them to be first generation Silmic's not Silmic II's - https://www.ebay.co.uk/itm/ELNA-35V...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649

    It looks like anchor handling operations are finally underway here (the one boat currently on attempt No. 3 to grapple the pennant for the first anchor mind) although there are conflicting wx reports for later today - I do hope we'll still get to watch the Scotland - Japan rugby match........


  11. Shadders

    Shadders pfm Member

  12. Richard Lines

    Richard Lines pfm Member


    Thanks for the pointers.

    I can't access the second site from here offshore, it'll need to wait until next week sometime. For now having sourced sufficient of the 2SD786/ 2SB737 devices I'll run with them.

    Given the general lack of interest in this subject currently I'm not minded to put much effort in over and above my own needs.


  13. Richard Lines

    Richard Lines pfm Member

    Good Evening All,

    I've now registered with Distrelec. Interesting how I find these devices via Elfa in Sweden then you register through the Netherlands and the price in Euro's is slightly higher than the SEK price. Ordering 30off the 2.2uF/ 63V Kemet SMR's would bring them in at about £2.30 each if I bought 30 dropping to about £2.25 for larger numbers.

    I've now secured 6off the Elna Silmic 47uF/ 63V capacitors.


  14. sq225917

    sq225917 situation engineer

  15. russel

    russel ./_dazed_and_confused

    Wouldn’t be any cheaper than paying elfa to post it to the U.K.

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