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Old 11th February 2007, 11:55 PM   #1
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Default Replace 2SK389 with other parts?

I have pretty much given up hope on obtaining the 2SK389 in order to repair an old Nakamichi amp. Knowing these are dual N-ch fets in one package, has anyone used 2 pieces of FETs (say 2SK170) to replaced 1 piece of 2SK389? Granted that some electrically characteristic may differ (slightly?) between these 2 parts, it is still better than thrashing the amp!
I am particularly seeking anyone who actually has done this before.

Thanks
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Old 12th February 2007, 12:27 AM   #2
Zen Mod is offline Zen Mod  Serbia
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Default Re: Replace 2SK389 with other parts?

Quote:
Originally posted by memorylane
I have pretty much given up hope on obtaining the 2SK389 in order to repair an old Nakamichi amp. Knowing these are dual N-ch fets in one package, has anyone used 2 pieces of FETs (say 2SK170) to replaced 1 piece of 2SK389? Granted that some electrically characteristic may differ (slightly?) between these 2 parts, it is still better than thrashing the amp!
I am particularly seeking anyone who actually has done this before.

Thanks

I know that even if you try to search here,your head will hurt in few hours of reading ..........
in short-yes,you can do it with two 2SK170.
try to match them before putting it in vivo

for matching......search .........here or in pdfs from Pass's site
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Old 12th February 2007, 12:42 AM   #3
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you can use a pair of 2sk170's -- i have seen these banded together with a ribbon of thin aluminum.
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Old 12th February 2007, 08:14 AM   #4
MRupp is offline MRupp  Germany
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You should try and match them closely, usually to within 1 mA Idss or less, if you have a batch of say 20 2SK170 it should not bee to difficult to get close enough values. Depending on how they are biased it might also make sense to use the same current range, i.e. GR/BL/V.
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Old 12th February 2007, 08:53 AM   #5
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You can find a couple of PDF files on JFET's on Borbely's site

http://www.borbelyaudio.com/special_articles.asp

Check it out.

Cheers.
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Old 12th February 2007, 09:28 AM   #6
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And you can buy the 2SK389 from Erno Borbely too.
http://www.borbelyaudio.com/pics/Compprice.pdf
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Old 12th February 2007, 10:37 AM   #7
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Memory Lane,

which type of Nak are you trying to repair ?

=> http://www.diyaudio.com/forums/showt...72#post1124672
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Old 12th February 2007, 11:17 AM   #8
lineup is offline lineup  Sweden
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Quote:
Originally posted by jackinnj
you can use a pair of 2sk170's -- i have seen these banded together with a ribbon of thin aluminum.

see attachment

this is the way I use to make a 'dual' transistor

sometimes I wrap a piece of thin copper sheet around them
before I put the wire clip around and tighten

if you want you can also put some silicon grease between transistors
but I think this is not ncessary
Attached Images
File Type: jpg 486_2b.jpg (99.7 KB, 394 views)
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Old 12th February 2007, 11:29 AM   #9
AndrewT is offline AndrewT  Scotland
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Hi Lineup,
glue the To92s together and then wrap two pieces of thick copper wire (1mm diam) around and twist off the ends for some dissipation.
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Old 12th February 2007, 12:29 PM   #10
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Line them Up North,

the pictures you post always have a high entertainment value.
On the other hand, you generally make me vision Heinrich Dorfmann. (Hardy Krüger, Flight of the Phoenix)

Model plane/train shops sell thinwall aluminium 1/3" diameter tubes, 0.4 mm wall thickness.
Some of them may offer online shopping on the web.
A little squeeze with some pliers on one side of a piece of tube and 2 face-to-face TO92s slide right in with a drop of thermal glue or a dab of silicon.
Looks much better, my sausage fingers would never get the tie strap fastener around the little critters anyway.
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