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-   -   NJL4302/4281 Discontinued. (http://www.diyaudio.com/forums/solid-state/214473-njl4302-4281-discontinued.html)

Dave Zan 14th June 2012 12:16 PM

NJL4302/4281 Discontinued.
 
I just realized that the NJL4281 & NJL4302 (ThermalTrak) are discontinued. The 3281 and 1302 are the stated "replacements" options. The 4xxx parts have better thermal conductance for more power, better Vce AND faster. So I just ordered 11.5 kilowatts of transistors before they become unobtainable. That should do me (it's only 50 after all).
So "heads up" to ThermalTrak users because there is not too much stock if ON Semi data is accurate.

David

Bonsai 14th June 2012 03:36 PM

Wow. That's incredible. They've only been available for a few years.

AndrewT 15th June 2012 12:28 PM

I'd guess the higher cost has suppressed sales to below economic production level.

Shame, since the 180W device has a poorer SOA at the higher voltages. The 230W device is really good when PSU is supplying >=+-60Vdc and still performs adequately @ around +-80Vdc

Bonsai 15th June 2012 02:56 PM

For discrete components like this, it's quite unusual for them to be EOL'd after such a short lifespan (other than low voltage mosfets in the computing market). Might be these are being discontinued because the assembly center is being moved and sales do not warrant the costs of transfer and requalification.

wahab 15th June 2012 03:16 PM

High manufacturing cost an low demand for theses devices.

Indeed , they are not that practical since they have no real equivalence ,
the Sanken s ones being different i think.

The lucky owners of amps with such devices will have trouble
servicing them with usual transistors since this will require adding
an accurate strip of external diodes although this solution works very well
once they are correctly selected.

Bonsai 15th June 2012 03:23 PM

Good thing then that I stuck with my SOT23 temp sense solution in the e-Amp. And with the NTC augmented 2 point calibration, it's really accurate and stable as well. :-)

jaycee 15th June 2012 03:40 PM

I think its a very simple reason - the market is limited, high power amps are all going class D, and indeed a lot of the market is. The true hifi sector of the market is growing smaller all the time.

Bonsai 15th June 2012 04:03 PM

Yes, that is true. Where will we be in 5 or 10 years?

I have heard many Class D amps. They are all crap. Period.

Dave Zan 16th June 2012 01:03 AM

Quote:

Originally Posted by wahab (Post 3060615)
The lucky owners of amps with such devices will have trouble
servicing them with usual transistors...

Note that other ThermalTrak transistors are still available so it should be possible to repair most amps. It is just the NJL4*** that are discontinued and these are the ones with best performance in every area. DIYAudio is full of perfectionists so I expected they would like to be warned.

Quote:

Originally Posted by Bonsai (Post 3060619)
Good thing then that I stuck with my SOT23 temp sense solution in the e-Amp. And with the NTC augmented 2 point calibration, it's really accurate and stable as well. :-)

Why did you do it that way? Your solution and ThermalTrak can both work well but yours seems a less obvious choice.


Best wishes
David

Bonsai 16th June 2012 01:12 AM

I got it working quite well on my Ovation 250 amp and it's been refined on th e-Amp and is now very good. I have taken a different tack to that recommended by RC and DS where they split the drivers from the power transistors and then sense the two separately. I put all the devices on the same heatsink and sense an output power device tab temp and use an NTC at the upper end of the operating temperature to pull Ibias back to the correct level. At ambient I have exactly 52mV across a pair of emitter resistors and at 65 C I also have 52mV. It's very stable across temp and the response is fast. There's some more detail on th technique on pages 40 & 41 of my e-Amp write up.


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