My Transistors, original or copy?

[jacco vermeulen]

as this company do work for army.

Say what ?

 

[Soundhappy]

Hi soundhappy,
The 8 watt Le Monstre looks quite interesting. I build until now some tube amplifiers, nevertheless I am not an "extremist" so transistors are an option as well. Actually I have some old fullrange speakers saved from Nordmende exquisite de luxe - one of the biggest and latest tube device made at Nordmende. This Nordmende had a tube amplifier with ell80 rated at about 8,5W per channel. Anyway, those speakers are really impresive - oval construction (about 33 cm / 24 cm) and might be an excellent candidate for Hiraga Le Monstre.
Is out there any safe source for the original transistors ?? at least all Jfets I could find on WWW looks like fakes.

http://www.diyaudio.com/forums/solid-state/5462-hiraga-le-monstre.html

Ask for jfet´s Spencer at

FET Audio | Hi-End Audio Projects

Best regards

 

[Juergen Knoop]

Oh, no bought fakes again.... 2SK170BL
First I ordered 10 pieces, they were the real stuff, so I bought another 100.....fakes.

Good fakes though, laserprinted, Yfs = 18 -19 mS, V ( pinch off) = -0.85V instead of max. -0.5V.
See picture... good one, fake one...

I'm not very familiar with JFETs and their parameter spreads. However I bought several '170s some time ago, so please excuse my curiosity. The Toshiba datasheet states a max. VGS(off) of -1.5V. So your transistors are still inside specifications?

 

[WalterW]

No, look at this graph...the real 2sk170 ( blue dots ) follow the specification exactly...the red fake JFET, what should I say....

Hmm, uploading pictures doesn't work at the moment

 

[ashok]

No, look at this graph...the real 2sk170 ( blue dots ) follow the specification exactly...the red fake JFET, what should I say....

Hmm, uploading pictures doesn't work at the moment

If you have trouble ,send it to someone reading this thread. They can re-post it !
Use the private email link......I guess that goes directly !(?)

 

[WalterW]

Ah, here is the graph....

 

[davidsrsb]

Much lower Gm, a different device

 

[AndrewT]

measure both Idss and Vpinchoff.
Borbely gave the circuit which switched between the two very quickly.

 

[Luke]

WalterW thanks for your post, I was considering buying these, but I'm not sure now

50pcs 2SJ74 BL Encapsulation to 92 P Channel Junction Type Low | eBay

I only do Idss categorising, it seems this is not enough these days. He gives full 14 day warranty, but it seems it needs proper testing to know for sure what it is.

 

[davidsrsb]

The bend in the red trace could actually be caused by heating. Rising jfet die temperature increases on resistance. Datasheet graphs are measured under pulse conditions

 

[wdecho]

WalterW thanks for your post, I was considering buying these, but I'm not sure now

50pcs 2SJ74 BL Encapsulation to 92 P Channel Junction Type Low | eBay

I only do Idss categorising, it seems this is not enough these days. He gives full 14 day warranty, but it seems it needs proper testing to know for sure what it is.

I would not buy them. The store still has C grade LSJ74's and matched pairs with the LSK170 in B grade will be stocked again soon. The consensus on this forum is the chinese 2Sk74's will be fake. My understanding is you can put some resistance on the source and bring the idss down but you will need to do some research on this forum to make sure I am correct.

 

[WalterW]

Don't buy them, most probably fake, 2sj74 is even harder to get than 2sk170....
I bought this from Ebay:

50pcs 2SK170 BL 2SK170 Original Toshiba FET N CH K170 2SK170BL | eBay

All 50 fakes! The picture on Ebay is of a real Toshiba part, for sure.
But what they sent me looks different, and they measure bad.
They look a lot like what I bought in the German shop, think he is getting them from Ebay too.

Walter

 

[WalterW]

Have requested a refund, I'm curious how they react....

 

[anatech]

Hi WalterW,
They have buyer protection. Make sure you escalate without too much delay.

-Chris

 

[WalterW]

Hi WalterW,
They have buyer protection. Make sure you escalate without too much delay.

-Chris

Thanks, I will.

 

[Luke]

I would not buy them. The store still has C grade LSJ74's and matched pairs with the LSK170 in B grade will be stocked again soon. The consensus on this forum is the chinese 2Sk74's will be fake. My understanding is you can put some resistance on the source and bring the idss down but you will need to do some research on this forum to make sure I am correct.

I have a few so Im not desparate, I did ask the vendor and he said they were definitely genuine. Its hard to know if they really know their products or are selling something they know nothing about.

 

[Luke]

Don't buy them, most probably fake, 2sj74 is even harder to get than 2sk170....
I bought this from Ebay:

50pcs 2SK170 BL 2SK170 Original Toshiba FET N CH K170 2SK170BL | eBay

All 50 fakes! The picture on Ebay is of a real Toshiba part, for sure.
But what they sent me looks different, and they measure bad.
They look a lot like what I bought in the German shop, think he is getting them from Ebay too.

Walter

Yes I think so too, if its too good to be true...

 

[Luke]

I have a few genuine K170BL I would trade for J74BL if anyone is interested.

 

[WalterW]

Just received my refund from Adeleparts2010. I thought I should also receive back the return shipping costs.... but it's OK with me.
The seller says I'm the first one complaining, and thus keeps offering them

 

[WalterW]

What is the source to avoid ?
Greetings

Darisus GMBH