Where to Find OLD JFets? 2SK146, 2SJ73, 2SK147, 2SJ72? - diyAudio
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Old 18th March 2010, 05:27 AM   #1
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Question Where to Find OLD JFets? 2SK146, 2SJ73, 2SK147, 2SJ72?

It's sad that the JFETs in one of my Denon amp are all busted. Some has S-D shorted and some has S-G and G-D opened. I need to buy all 4 JFET devices and wondering you folks might have some good indication.

I know PartStore might have some but I don't know if they can find them. I've made an order in a couple of places but not sure they can find them.

If you know any source for these JFETs, please post here.

Thanks All!
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Old 18th March 2010, 05:48 AM   #2
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Borbely Audio
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Old 18th March 2010, 05:59 AM   #3
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Thanks John! You are very kind. I will contact Borbely Audio and hope they can help.

Edit : I just found that Borbely Audio is not in the States. Any possible chance of U.S sources?

Thanks again,
James M.

Last edited by megasat16; 18th March 2010 at 06:04 AM.
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Old 18th March 2010, 06:08 AM   #4
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Silly me that I forgot to post Hfe rank and quantity of what I need in my first post.

Qty 2 x 2SK146-BL
Qty 2 x 2SJ73-BL
Qty 2 x 2SK147-GR1
Qty 2 x 2SJ72-GR1
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Old 18th March 2010, 10:15 AM   #5
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by megasat16 View Post
It's sad that the JFETs in one of my Denon amp are all busted.
is that because the Denon designers chose the wrong operating conditions for a poor choice of adopted device?
Maybe you could make this equipment more reliable by choosing a modern equivalent that can avoid the failures you have found.
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Old 18th March 2010, 10:47 AM   #6
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Try mcmelectronics, in usa I think, they are also part of denon oem service part distribution sales and get their denon oem parts from denon company. You could also contact a denon dealer which could provide further info.
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Old 18th March 2010, 02:25 PM   #7
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Default Replacements part numbers

Search for those part numbers in these post. Somewhere recently someone listed the exact replacement part numbers from Hitachi for these parts. Look in parts and amplifiers.
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Old 18th March 2010, 05:15 PM   #8
h_a is offline h_a  Europe
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These jfets are pure unobtainium for decades now (these are 80ies parts). Borbely is the only one that still stocks them - understandably at a premium.

Some have 1:1 replacements like the 2SK146-BL which is now produced as 2SK369 and is also hard to get. Worse, there are no complements (the 2SJ-parts). The K147 is a dual K146 and may be replaced by matched K369.

Otherwise there are no such jfets today that have the low noise and high transconductance of these parts. All you could do is to try to use K170/J74 which are now also discontinued. Likely you lose gain as these parts are likely used for a reason.

Have fun, Hannes

PS: or get a 2nd hand Denon...
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Old 18th March 2010, 08:14 PM   #9
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Quote:
Originally Posted by AndrewT View Post
is that because the Denon designers chose the wrong operating conditions for a poor choice of adopted device?
Maybe you could make this equipment more reliable by choosing a modern equivalent that can avoid the failures you have found.
Andrew, I am not sure if Denon made a poor choice selecting these JFets in the first place. But the design calls for a single stage gain with high Gm in the input FETs with only one gain stage to drive the output. I think it should last a lifetime unless the Preamp screwed up and sends off High DCV to kill the JFETs in the amp.

I bought the amp damaged and it seems the previous owner had a nasty preamp failure on one channel. I am not even sure why the cap in the input of the amp doesn't block DC too.

I can't even seem to find enough info on these JFETs to look for subs. I am going by what other people have thought the close sub for these devices if there is any.

Quote:
Originally Posted by homemodder View Post
Try mcmelectronics, in usa I think, they are also part of denon oem service part distribution sales and get their denon oem parts from denon company. You could also contact a denon dealer which could provide further info.
I tried MCM but everything is back ordered. I tried ordering from Encompass Parts and hope they can find them. I also send an email to Borbely Audio and awaiting for their reply.

Quote:
Originally Posted by sumaudioguy View Post
Search for those part numbers in these post. Somewhere recently someone listed the exact replacement part numbers from Hitachi for these parts. Look in parts and amplifiers.
Yes, some Vintage Hitachi and Sansui seems to use these FETs too so I tried ordering with both Denon and Hitachi part numbers from a few places.

Quote:
Originally Posted by h_a View Post
These jfets are pure unobtainium for decades now (these are 80ies parts). Borbely is the only one that still stocks them - understandably at a premium.

Some have 1:1 replacements like the 2SK146-BL which is now produced as 2SK369 and is also hard to get. Worse, there are no complements (the 2SJ-parts). The K147 is a dual K146 and may be replaced by matched K369.

Otherwise there are no such jfets today that have the low noise and high transconductance of these parts. All you could do is to try to use K170/J74 which are now also discontinued. Likely you lose gain as these parts are likely used for a reason.

Have fun, Hannes

PS: or get a 2nd hand Denon...
Hannes, I think you are quite right about 80s devices. New Old Stock of them are really hard to find and hope I can buy them if I paid a premium price for them. If not, I can find old junkers for donor parts but it's going to be very costly and time consuming.

As for getting another Denon, it's even harder to buy one than the JFETs as the amp itself is unobtanium nowadays.
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Old 18th March 2010, 08:26 PM   #10
uli is offline uli  Austria
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what is easily available and a perfect match to K170/J74 is K371/J108

except of the smaller case they are identical. just use 2 of them instead one K147/J72 and matched quads instead of K146/J73

cheers Uli

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