Pioneer SA9800 Phono stage, SK131S source?

[tutor_turtle]

Got a SA9800 in for a bad phono stage.
Traced it to a bad dual J-FET: SK131S.
Seems to be yet another part made of unobtianium.
Has anyone tried an SK170 with any success?

 

[TomSc]

Have not tried the SK170 myself, but Nelson Pass thinks it may be a suitable sub.

Looking for jFET sub for 2SK131?

Looking for suitable replacement FETs to match to replace this double j-fet package? It's a differential pair for my phono mm card in a Sansui AU-X11. Not having any luck? 2N5247 was listed as a good sub, but it's long gone now too?

www.diyaudio.com

 

[tutor_turtle]

Have not tried the SK170 myself, but Nelson Pass thinks it may be a suitable sub.

Looking for jFET sub for 2SK131?

Looking for suitable replacement FETs to match to replace this double j-fet package? It's a differential pair for my phono mm card in a Sansui AU-X11. Not having any luck? 2N5247 was listed as a good sub, but it's long gone now too?

www.diyaudio.com

Thanks.
I bought a lot of 10.
How closely do they need to be matched? I have that nice PEAK transistor checking tool.
The circuit does have a balancing trim pot, but no clue how to adjust it.
The service manual seems to have skipped over this adjustment.

 

[dlucy]

The adjustment procedure is on page 18 of the SA-9800 service manual. You can find a copy here in the AK database: https://akdatabase.org/AKview/albums/userpics/10004/Pioneer SA9800 Service.pdf

 

[tutor_turtle]

The adjustment procedure is on page 18 of the SA-9800 service manual. You can find a copy here in the AK database: https://akdatabase.org/AKview/albums/userpics/10004/Pioneer SA9800 Service.pdf

Thank you,
However, those are the instructions for setting DC balance and Bias on Driver board: GWH-119.
On the phono board (GFW-116) the are two trim pots, VR-3 & VR-4, that set the balance for FETs Q16 & Q17, respectively. (See Page 31)
First gain stage for MM phono input.

 

[JoseHH]

Have you considered addapting the 2SK2145? In this situation this part should work, with a small addaptor board.

 

[kwayde]

Thank you,
However, those are the instructions for setting DC balance and Bias on Driver board: GWH-119.
On the phono board (GFW-116) the are two trim pots, VR-3 & VR-4, that set the balance for FETs Q16 & Q17, respectively. (See Page 31)
First gain stage for MM phono input.

Page 19 in the manual linked in post #4.

EQ amplifier.

 

[dlucy]

Have you considered addapting the 2SK2145? In this situation this part should work, with a small addaptor board.

@tutor_turtle if you choose to go this way, a "how to" is here on AK: https://audiokarma.org/forums/index...through-hole-transistor-replacements.1079170/

 

[tutor_turtle]

Page 19 in the manual linked in post #4.

EQ amplifier.

I Missed that.
Thank you so very much.
Parts are due to arrive today.