i have a sony stereo electret condenser from the 70s. one of the transistors has failed but i cannot identify the transistor. can anyone help?
the code reads K39A CI2

the microphone is an ecm 99 if that helps.

 

i have a sony stereo electret condenser from the 70s. one of the transistors has failed but i cannot identify the transistor. can anyone help?
the code reads K39A CI2
View attachment 305517View attachment 305518View attachment 305519
the microphone is an ecm 99 if that helps.

2SK39A N J-FET

 

2SK39A N J-FET

Thanks, do you know where I can buy one of those or the modern equivalent?

 

Thanks, do you know where I can buy one of those or the modern equivalent?

No, I don't unfortunately. Have a look at the following website topic which might give you some ideas:

https://www.eevblog.com/forum/projects/jfet-for-electret-mic-follower/

Good luck.

 

No, I don't unfortunately. Have a look at the following website topic which might give you some ideas:

https://www.eevblog.com/forum/projects/jfet-for-electret-mic-follower/

Good luck.

There they mention pulling the jfets out of electret capsules, do you know if that's reffering to the small ones you can buy for projects?

 

do you know where I can buy one of those or the modern equivalent?

I found this cross reference:

at https://masterelectronicsrepair.blogspot.com/search?q=2SK39A

I looked up specs for 2SK103 and found:

at https://www.web-bcs.com/transistor/tfet/2s/2SK103.php?lan=en

That lead me to Vishay J102, which is obsolete, but Mouser has some J201 from InterFET that look compatible:
https://www.mouser.com/ProductDetail/InterFET/J201?qs=OxRSArmBDfyvD8SbvWteMw==


You can get a surface mount device for 10% of the price of the through hole part.

You can get these adapters for about a dime:

The leadframes are a dime each, if you can find them. You can substitute right angle male headers if the holes in the board are large enough. If it's a single sided board, you could enlarge them with a 0.035" (#65) drill bit.

If you have some copper clad board and a Dremel tool, you can make your own (shorter ones):

 

Farnell has 2SK596.

https://uk.farnell.com/onsemi/2sk596s-c/jfet-transistor-n-ch-1v-150deg/dp/4182192

 

Sony ECM99 Microphone