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Old 27th February 2006, 09:08 AM   #11
ilimzn is offline ilimzn  Croatia
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Well, the gm is not THAT low, comparable or even slightly higher than their competitor that eventually drove them out of the market, LMOS, i.e. laterals. The main reason was the manufacturing process for laterals is is very similar to what was normally used for most semiconductors at the time, whereas the VFET process was quite different, and MUCH more expensive.
VFET, however, have a very low Cgs compared to modern MOSFETs, about 150pF for the 10A/250V Sony device used in their class D amp.
VFET are true power JFETs, SITs in general have no PN junction between the channel and the gate but use a metal interface. That being said the terminology becomes somewhat blurred as different topologies come about.
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Old 27th February 2006, 10:56 AM   #12
mtlin12 is offline mtlin12  Taiwan
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YAMAHA B-1 schematic as attachment


http://www.sm.rim.or.jp/~konton/B-1.gif

2SK77 I think can replaced by NEC 2SK70, only 2SK70's Vdsx=100V and also hard to find.
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Old 14th February 2008, 07:31 AM   #13
mujulee is offline mujulee  Taiwan
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Default yamaha b-1

I have trace the pwoer supply circuit, Is someone need it? Please mail me: duan.lee@msa.hinet.net
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Old 6th November 2009, 05:26 PM   #14
ECS21 is offline ECS21  Canada
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Hey mtlin12, the link is forbiden, Currently have a B-1 for repair and need the schematic too. Will appreciate it much if you could please fix the link or post it, thanks.
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Old 6th November 2009, 06:15 PM   #15
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http://www7b.biglobe.ne.jp/~konton/B-1.GIF
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Old 6th November 2009, 06:49 PM   #16
mos57 is offline mos57  Italy
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Vfet are rare today, but 2SK77 is unique, bigger, and very very rare Vfet.

You can try to substitute it only with the TOKIN/NEC 2SK180 I think, but this last is also very rare.

YAMAHA B1 schematic from my site : http://www.amplimos.it/images/Yamaha%20B1.jpg

Francesco
Attached Images
File Type: jpg 2SK180.jpg (120.4 KB, 756 views)
File Type: jpg 2sk180_2sj18.jpg (36.1 KB, 718 views)

Last edited by mos57; 6th November 2009 at 07:04 PM.
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Old 6th November 2009, 07:02 PM   #17
ECS21 is offline ECS21  Canada
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Thank you very much for the fast reply.
Do you also have the schematic for the power supply section???
thanks in advance.
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Old 6th November 2009, 08:08 PM   #18
mos57 is offline mos57  Italy
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Ooops!!! The above link is only a principles schematic.

In the following the detailed design for Yamaha B1:

http://www.amplimos.it/images/2sk77%20amp%20YAMAHA%20B-1.gif

If everyone have interesting, also i have the datasheet and the curves for 2sk180

Francesco.

Last edited by mos57; 6th November 2009 at 08:12 PM.
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Old 7th November 2009, 05:21 AM   #19
ECS21 is offline ECS21  Canada
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Thanks mos57,
Much appreciated.
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Old 7th November 2009, 09:51 AM   #20
tvi is offline tvi  Australia
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digital-do-main use these
Click the image to open in full size.
2SK77B in their amps, but I think they are custom/exclusive to them?

Regards
James
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