Help with replacement fets 2sk1529/2sj200

[BesPav]

When Vertical fets as well as BJT's gets warmer Vgs and Vbe changes and more current will flow.
Bias network usually compensates for it.

Lateral fets works the opposite way, and sort of compensates it self, and less current flows as it gets warmer, or Vgs is rising.

Being furthermore clearly this issues are mostly depends of thermal stability point.
Both laterals and verticals have that point, but while laterals could be thermally stable at ~100 and higher mA bias, the verticals have that point really huge - at tens of Amperes or even dozens. So out of real bias point.



There are a known issue - laterals are stable while verticals are not, but really things a little bit complicated.

 

[suzyj]

Q112 is a conventional Vbe multiplier, so assuming that’s connected to the heatsink it probably doesnt matter whether the drivers are lateral or vertical mosfets.

Odd design though. I’d have used multiple lateral MOSFETs as the final output with a BJT driver. I guess tis way is cheaper, but still allows you to advertise that the amp has the mosfets.

 

[BesPav]

Odd design though.

Repair, sell and buy one of chinese LabGruppens:

 

[Trollet]

I bought 2sj200 and 2sk1529 from Kessler electronic in Germany.
They are genuine.

BR

Figge

 

[fab]

Hi Dan
Any progress on your repair? Have you used the 2SK1530/2SJ201?
Fab