Luxman M-02 Dual-FET

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Chavagnac
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#1 erstellt: 03. Mrz 2012, 15:46

Hallo from France,
I need one 2SK389 BL Toshiba transistor for my Luxman M-02 amplifier.
I would like to know where i could buy one of this transistor (not really easy to find, exept in Asia, but perhaps fakes?)
If somebody have one in his stock it would be fine, for a reasonnable price.
Danke for response.
Dom

daStephen
Gesperrt

#2 erstellt: 03. Mrz 2012, 21:56

Ask

Dieter

Poetry2me
Inventar

#3 erstellt: 04. Mrz 2012, 00:57

Hi Dom,

should you not find the original type and seek replacement you may be able to find modern types which have different casing but should match the electrical parameters.

You are looking for something like "Low Noise Monolithic Dual N-Channel Junction FET".
These guys seem to have it:

http://www.linearsystems.com/data_sheets.html

Take a look at LS845 or similar types in this list.
A little tweaking with some adaptor may be required though.

Good luck, let us know.

- Poetry2me

Poetry2me
Inventar

#4 erstellt: 04. Mrz 2012, 01:13

Found this:

http://www.donberg.de/katalog/2sk_389bl.html

Chavagnac
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#5 erstellt: 04. Mrz 2012, 09:48

Hallo,
Thanks a lot for responses.

In fact, i have repaired this faulty amplifier that i bought(in your country) it few months ago.(i like Luxman i have a l-430 too)
One channel was broken: some résistors, some little transistors and a pair of famous c3281/a1302.
OK it works fine now.

As i think quality power supply is important (1983--->arround 30 years old) i decided to change all chimical capacitors with Nichicon Audio capacitors.

Then, recently i notice that in the past, the other channels has been repaired too:
The input Dual Fet transistor is not 2SK389 BL but a 2SK129A with metal package.

Of course it works but i wonder if it is so critical.
I have no notice a different sound
As it works , perhaps its not a good idea, but in my mind i'm looking for original pieces.
Have a nice day.

Poetry2me
Inventar

#6 erstellt: 04. Mrz 2012, 10:35

Hello Dom,

this wonderful power amp deserves new capacitors. In a number of cases, I have verified myself that new and somtimes also enlarged capacitors improve channel separation and impulse behaviour, as better bass control.

In my investigations about the Monolithic Dual FET transistors I have found several types mentioned to be replacable:

2SK389 == 2SK129A == µPA68H

All of these dual FET transistors seem to be ultr rare and very hard to find. If someone get one it ist mostly for 20 EUR a piece or more.

One hint was that Linear Integrated Systems produces it's own version of the 2SK389: the LSK389 but only in metal case aswell.

http://www.linearsystems.com/datasheets/LSK389.pdf

All that said:
The metal case is really superior to the plastic one of the original.
2SK129A seems to be quite similar in electrical characteristics to the 2SK389BL
ALso, for low distortion, it is more important to have optimal equality of the pair than to have specific values of I_DSS or such parameters.

My recommendation:
Leave the 2SK129A in there. It should be close to perfect if not superior.

- Poetry2me

Chavagnac
Schaut ab und zu mal vorbei

#7 erstellt: 04. Mrz 2012, 14:09

Hallo Poetry2me,
Ok, i understand.
So i will continue to change all capacitors include the two big of the power supply that will give me mecanical work due to higher lenght.
After i will do all soldiers of the PCB, due to the age they are very bad.
After ..a new power amplifier for long time.
Thanks for your reply.
Regards