Where to Find OLD JFets? 2SK146, 2SJ73, 2SK147, 2SJ72?

Status
Not open for further replies.
Jump to Latest
M

megasat16

Member
Joined 2009
#1
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. :up:

Thanks All!
 
#3
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:
#8
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...
 
#9
AndrewT said:
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.
Click to expand...

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.

homemodder said:
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.
Click to expand...

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.

sumaudioguy said:
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.
Click to expand...

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.

h_a said:
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...
Click to expand...

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.
 
#11
uli said:
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

:nod: :nod: :nod:
Click to expand...

Thanks for the tips! Sounds like a plan if Borbely Audio can't help me with the ones I need.

Pd for the K146/J73 is 600mWx2 so I might need triplet of these in each device. All other characteristics looks very close too.

Any likely complication (DC Offset imbalance?) or noise figure increased or oscillation for using stacked triplets or duplex of these FETs?
 
Last edited:
#13
john curl said:
If I were you, I would order just the parts that you need for repair from Borbley. Most here do not have the knowledge necessary to help you. Where are you located?
Click to expand...

Yes John! I intend to order from the Borbely Audio and still awaiting for their reply. As long as I can buy the parts I need, I don't mind paying the premium price for it. The Denon Monobloc is pretty useless without these FETs.

I am in Los Angeles, CA.
 
#19
mlloyd1 said:
not as efficient at generating big $$$ as RAM & micro controllers

mlloyd1
Click to expand...

Sadly but true. Besides, everything nowadays is SMD based so through hole components are not very profittable to make anymore.

Having said that, I thought Tosh may have sold these or licensed these to NEC or Fujitsu or other semi makers. I am surprised why there is no other sub for these through hole packages for low noise, High Gm and good Pd JFETs not in production nowadays.
 
Last edited:
Status
Not open for further replies.
Top Bottom