MosFet replacements for Kyocera R-851 ???

[dogwan]

I need help locating replacement output MosFet's for an R-851.

Looks like stock pairs are 2sk272 and 2sj92.

My particular unit has a mix of ....
2sk405 with 2sj115, and 2sk400 with 2sj114

I've read on one post on another forum that 2sk1529 and 2sj200 are modern equivalents. But, they show up as obsolete on Mouser.

I see 405/115 and 1529/200 pairs for sale on Ebay for not (overly) ridiculous prices from US sellers. How legit do you think these sellers are? I know better than to source from offshore on these.

Suggestions???? I will need 4 pair to replace entire output section. I am not sure of quality of working devices, so will just replace all if I can find legit replacements.

I'm hoping I can get a drop in suggestion without having to modify the surrounding circuitry. I'm a good parts swapper, but pretty much a layperson when it comes to figuring out circuits. So, please keep it simple if you can.

Thanks.

 

[dogwan]

PS, forgot to mention that someone had previously tried to replace the 2sj115's with 2sj162 (not me) and I have since learned the 162's are lateral MosFet with a different pinout. I'm guessing that's why the unit came to me fried.

 

[BesPav]

Suggestions?

IRFP240/9240.

Before of soldering check if you can increase bias voltage from ~1,8 V for 1530/201 to ~4,2 V for 240/9240.

 

[dogwan]

IRFP240/9240.

Before of soldering check if you can increase bias voltage from ~1,8 V for 1530/201 to ~4,2 V for 240/9240.

Oy, I was hoping to avoid modifying the circuit.

Here is a screen capture from the PDF I have of the service manual. This shot shows the section with the output MosFet's (Q01-08).

It looks like to me that they are biased with 2.0v dropped thru R544-547 (470Ω) to 1.5v. I don't see any way to increase that to 4.2v as you suggest.

But like I said, I'm a little inexperienced.

 

[Trollet]

You can get SJ200 and SK1529 at Bdent.com for example and some places in europe.
They work great as replacements for K405 and J115.

Regards

Figge

 

[BesPav]

I was hoping to avoid modifying the circuit.

No, circuit will stay the same. Just change some nominals.

This shot shows the section with the output MosFet's (Q01-08).

Correct. 😉

It looks like to me that they are biased with 2.0v dropped thru R544-547 (470Ω) to 1.5v. I don't see any way to increase that to 4.2v as you suggest.

No, R544-547 is just a gate stoppers avoiding from capacitive loading for previous stage. And at DC there are no current through theese resistors due to isolated gates.

They biased by voltage drop at R543 which caused by Q519-520 quiescent current.
In its turn this current provided by even previous stages output DC voltage, those stages to the left side and unfortunately cropped.

So you need first to keep bias current through Q519-520 by increasing previous stage output DC voltage and simultaneously increase R543 to provide more bias voltage for output devices.


Oh!
Just ask there:
Selling Zhou Fang’s remaining stocks including some very rare Toshiba transistors

Selling Zhou Fang’s remaining stocks including some very rare Toshiba transistors

 

[dogwan]

Oh!
Just ask there:
Selling Zhou Fang’s remaining stocks including some very rare Toshiba transistors

Selling Zhou Fang’s remaining stocks including some very rare Toshiba transistors

Thanks for the lead. Assuming I can use the 2sk1530 and 2sj201 pairs then this may be the way I go instead of IRFP240/9240. I'm sure I could figure out what you're talking about, but not sure this project would justify the time I would have to invest.

 

[dogwan]

You can get SJ200 and SK1529 at Bdent.com for example and some places in europe.
They work great as replacements for K405 and J115.

Regards

Figge

Thanks Trollet!

BD Enterprises has both the SJ200/SK1529 and the SJ201/SK1530 pairs. Not cheap. I assume there is confidence these are not fakes at those prices.

I also assume I can use the 201/1530's just as easily since I understand they are the direct replacements for when the 200/1529's were discontinued?


The link that @BesPav linked to selling Zhou Fang’s remaining stocks has matched sets at similar prices to BD Enterprises. My question is ... how important is matching?

My goal is to get this receiver working at least on par as when it was stock output transistors. How closely would they have matched from the factory? This will realistically be used as a receiver in my living room. Not in a critical listening situation.