AndrewT can you please post a high quality Macro photo of your genuine devices. I will do the same with the ones that I think are genuine.
The pirates and thieves are out there to get us poor mortals.
Can we not help ourselves by trying to design using CURRENT and COMMONLY AVAILABLE parts.
All PIRATING is driven by a shortage of supply or the COST of RARE components.
Surely semiconductor manufacturers are trying to improve their products.
There MUST be a commonly available alternative to most devices - ICs maybe not, but discretes I would say there must be.
The 2SK170BL and the 2SJ109 have become almost unobtainable. We are inviting the counterfeiters to see us off by still ordering them.
The last few threads on counterfeit devices have been so obvious its comical. Unfortunately you wont know until you receive them. These devices have been so clearly sanded (abraded) of their original part number that a 6 year old could spot them.
That is not a slur against us, we are only buying them. If we dont buy them, the counterfeiters will go out of business.
Can we not help ourselves by trying to design using CURRENT and COMMONLY AVAILABLE parts.
All PIRATING is driven by a shortage of supply or the COST of RARE components.
Surely semiconductor manufacturers are trying to improve their products.
There MUST be a commonly available alternative to most devices - ICs maybe not, but discretes I would say there must be.
The 2SK170BL and the 2SJ109 have become almost unobtainable. We are inviting the counterfeiters to see us off by still ordering them.
The last few threads on counterfeit devices have been so obvious its comical. Unfortunately you wont know until you receive them. These devices have been so clearly sanded (abraded) of their original part number that a 6 year old could spot them.
That is not a slur against us, we are only buying them. If we dont buy them, the counterfeiters will go out of business.
the problem with using modern devices, is that existing circuits may need to be tweaked to use the modern components. if i use more modern output transistors in place of obsolete ones, it's likely i need to recalculate the original compensation caps to keep the amp stable when using transistors that have a different Miller capacitance. it's not a difficult change, but it's one few are aware of, and the difference in Miller capacitance can make an amp oscillate.
however, we should be paying attention to companies like Fairchild and ON that are licensees of obsolete processes, tooling, and part numbers, as discontinued transistors are often added to these two company's repertiore. also, using reputable distributors, rather than buying from "E-Slay", or from what we used to call "phone booth" brokers, would alleviate a lot of the trouble. and as the old saying goes, "if you think it's too good to be true, it probably isn't".... stop jumping at the chance to get 2SC5200/A1943 devices for $2.00 each.
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And after a short while, They will start producing whatever we are using instead
I'ld say:
They will keep on labeling whatever we are raving about instead.
In fact, I once heard that because there are often such wide dispersions in production, the rejects are labelled in a category that fits the remaining specs.
Back to my 2SK170BL fakes. I bought them for the going rate from Dalbani.com, a reputed distributor.
No-one is safe.
No-one is safe.
Im intigued as to what my Fake 2SK170BL actually are.
At a pure guess they are 2SK170GR - what is the best way to measure these devices for passive parameters ?
I've got a MM that can measure capacitance. I don't want to go to too much bother in testing them, but if they are 2SK170s I might still be able to use them.
At a pure guess they are 2SK170GR - what is the best way to measure these devices for passive parameters ?
I've got a MM that can measure capacitance. I don't want to go to too much bother in testing them, but if they are 2SK170s I might still be able to use them.
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Can you suggest a simple circuit to measure gm. Idss has already been established to lie within the normal range of the GR version.
Say transconductance is 20mS, is 20mA for 1000mV, aka 50mV per mA.
Simple 5Vdc power supply (LM7905), and a voltage divider (trimpot + resistor) on the JFET gate.
(plus a resistor on the JFET drain to measure the current)
Simple 5Vdc power supply (LM7905), and a voltage divider (trimpot + resistor) on the JFET gate.
(plus a resistor on the JFET drain to measure the current)
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Could you provide a simple drawing for us oldies.
I'm OK with transisitors but I'm not familiar with FETs. I wouldn't have asked the question if I knew the answer.
There are too many people here who like to say "I am clever and I could do it." Could some of them try providing a few answers.
http://www.tkhifi.com/div/Erno_Borbely_fet_articel_1.pdf
there's a tester shown, but it shows "conceptual" current sources, so you'll need to "roll your own"
theres also a previous thread on diyaudio http://www.diyaudio.com/forums/solid-state/166099-accurate-measurement-jfet-gm.html
there's a tester shown, but it shows "conceptual" current sources, so you'll need to "roll your own"
theres also a previous thread on diyaudio http://www.diyaudio.com/forums/solid-state/166099-accurate-measurement-jfet-gm.html