Successors for V-FET SONY-Yamaha-TOKIN 2SJ28, 2SJ18/2SK60, 2SJ26/2SK76 and 2SK180

[Lumba Ogir]

tiefbassuebertr,
please get it right, there are no successor devices. I would try to replace them with lateral MOSFETs.

[h_a]

Originally posted by Lumba Ogir
I would try to replace them with lateral MOSFETs.

Err, you are not serious about this, right?

Have fun, Hannes

[Lumba Ogir]

Hannes,
what would you do?

[kenpeter]

Since SITransistors have Mu, might attempt replacing them with
a Triodlington arrangement of Vacuum Triode + Bipolar? Cathode
to Base, with Plate and Collector tied together.

Though it might be difficult finding a Triode that doesn't leak too
much at the grid when the plate voltage is drawn extremely low...

The idea that the triode provides tight local 1/(Mu-1) feedback
of collector voltage to the base... Thus the collector inherits the
triode's voltgage linearity.

If there is a small signal version of SIT or V-Fet (perhaps for RF?)
you might fudge some sort of a SITlington for similar inheritance
the rule of Mu to a power bipolar device...

The bipolar mentioned above, could just as well be enhancement
MOSFET, with a bleed resistor from gate to source... Its just there
to amplify current, Voltage gain linearized by the watchful eye of
Mu.

[h_a]

Originally posted by Lumba Ogir
Hannes,
what would you do?

Well, either you pay the big bucks for genuine parts (not for the faint heart certainly) or you get/build yourself a new amp. IMHO it's not worth the time to rework one of these pretty complex amps for different outputs.

And even if you did, chances are that some of the tons of other transistors in that amp also die at some point

Yamaha B1:
4x 2SK77 V-FET (non-complementary)
39 FETs
113 transistors
64 diodes
7 Zener diodes

Seeing these numbers one wonders how the outputs can dominate the sound, though.

Have fun, Hannes

[Lumba Ogir]

Hannes,
I was not aware of the details, see a simpler design below, lateral MOSFETs can be biased conveniently (with a resistor).

[h_a]

Where do you have this circlotron from?

[Lumba Ogir]

From a Japanese site, I don`t have the link, was having minor difficulty following the description.

[h_a]

You sure the power supply belongs to that circuit? In the schematic V1+V4 read as 30V, but are clearly voltage doublers (60V) in the psu-schematic.

Have fun, Hannes

[Lumba Ogir]

It should, lying in the same folder here...