• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Luxman L-31: what closest outputs to use for 2SB531 / 2SD371 ?

david winter

david winter

Classical music lover.
Hi,

One channel blew the fuses due to one shorted output and the other almost shorted. These are Toshiba 2SB531 and 2SD371. Any opinions on the closest equivalents without changing the circuit ? These seem to be not very common and most of those proposed on the bay are fakes. I'm putting the schematic of the output section.


Thanks,

David
 

Attachments

  • L31.gif
    L31.gif
    41.7 KB · Views: 92
Register to hide this ad
david winter said:
Are you sure they will replace the 2SB/2SD without trouble ? Their data seem quite different.
Click to expand...

Oh yes..The Onsemi's are just beefier and will handle more voltage-current . Drop in replacements ..Work fine ,last a long time..

Or you could go with these Onsemi's which are a little closer to the same specs as originals.
MJ15015G for 2SD
MJ15016G for 2SB

If it was mine I would use the MJ21193's and 94's...
 
Last edited:
Well, thanks a lot for your great advise. They work like a charm.
However I'm surprised to see the heatsink heat quite a lot but at the same time I made this test at mid-volume (or a bit over).
At least both channels seem to heat equally by "touching" each transistor.
For the heck of testing I left the good channel with its 2SB/2SD and the other with the new ON. Works great this way !
I also set the idle current to 45mA as per service manual. This looks much higher than the usual 25mA I has to set in other amps but if it's what they tell, that's how it has to be.
I was also surprised to see +/- 50mV mentioned for the zero DC output range. I set it to 0 on both channels (give it 1mV more or less).
 
Hi all, 1st post, dredging up old thread.
I too am rebuilding a Luxman L31 with a dead power tranny.
@david winter seems to have had success with @avionic recommedation of:

MJ21193G for the original 2SB537
MJ21194G for the original 2SD371

Before going the same path I find myself wondering how close a match these subsitutes are and whether the circuit can be further optimised in some way to accomodate the MJ2's.
and was hoping someone more tech savvy than me could have a look. Schematic is in the 1st post. One question is should the idle current stay at the stock 45mA?

Maybe there are better choices now available in TO-3 package?

(originally tried to order
MJ15015G for 2SD
MJ15016G for 2SB
but the 16G's seem NLA)

Thanks
 
adrenal said:
Thanks avionic.
They seem to be plug 'n' play substitutes but might some further tweaking be in order?
Click to expand...
No.. TO-3 is a TO-3 ... Other than setting the idle current ( bias ).. And adjusting DC offset if there are provisions for doing so.
 
avionic said:
No.. TO-3 is a TO-3 ... Other than setting the idle current ( bias ).. And adjusting DC offset if there are provisions for doing so.
Click to expand...

Yes, there is provision to adjust both. Idle current for the original 2SD and 2SB's was 45mA. Same for the MJ2119's?
 
Hi all i am new to this and have a silly question , i have a L31 with both 2SD371 gone apparently ( basic tester pin check ) , the 2SB seems to be doing ok , as i was trying to source some modern equivalent i stumble upon this gold mine of information , so my question is since both 2sd are donw can i just pair my remaining working 2SB with some MJ15015G ? or do i need the matching complementery necessarally ?
 
gwendal said:
Hi all i am new to this and have a silly question , i have a L31 with both 2SD371 gone apparently ( basic tester pin check ) , the 2SB seems to be doing ok , as i was trying to source some modern equivalent i stumble upon this gold mine of information , so my question is since both 2sd are donw can i just pair my remaining working 2SB with some MJ15015G ? or do i need the matching complementery necessarally ?
Click to expand...
No. Replace them both.

You'll need MJ21195G and MJ21196G as the others are out of stock most places.
 
ivandezande said:
No. Replace them both.

You'll need MJ21195G and MJ21196G as the others are out of stock most places.
Click to expand...
Thanks very much for your reply ^^ , i am currently recaping the whole board for elctrolitycs , i plan on upscaling the 3300 uf to at least 4700 uf or maybe even more now i read that upscaling those imply i may have to upscale the bridge diodes capacitance aswell ?
 
Also these 3300 uf that were originally on the board have 3 terminals , most caps nowadays only have two .. the third terminal isnt a second plus like i thought it could be .. How can i implement this with modern 2 terminal caps ?
 
gwendal said:
Thanks very much for your reply ^^ , i am currently recaping the whole board for elctrolitycs , i plan on upscaling the 3300 uf to at least 4700 uf or maybe even more now i read that upscaling those imply i may have to upscale the bridge diodes capacitance aswell ?
Click to expand...
No going to 4700uF should be fine.
Either drill holes or extend leads. Third lead is for stabilization.
 
ivandezande said:
No going to 4700uF should be fine.
Either drill holes or extend leads. Third lead is for stabilization.
Click to expand...
ok great ! will just do that then ! Stabilization you mean so it holds in place ? its weird cause igot different mesurement from that pin to ground ... I was thinking it was a double value cap altoought it doesnt say any thing outstanding
 

Attachments

  • DSC_0070.JPG
    DSC_0070.JPG
    60.5 KB · Views: 12
  • DSC_0071.JPG
    DSC_0071.JPG
    40.4 KB · Views: 12
gwendal said:
ok great ! will just do that then ! Stabilization you mean so it holds in place ? its weird cause igot different mesurement from that pin to ground ... I was thinking it was a double value cap altoought it doesnt say any thing outstanding
Click to expand...
Yes just holds in place. It’s not connected to anything. Look at the traces.
 
You must log in or register to reply here.
Back
Top Bottom