Salas, do you know if anyone other than NEC producing the uPA68HA? The reason that I ask is that I have recently bought what had been promoted as NEC product that is marked SINGA on the back side. There are no NEC specific markings. Are these parts in fact NEC made in 'SINGA'PORE or a substitute?
Carl hi,
The versions I have, and I have not seen any other version offered, are those two in the picture I uploaded before. See post#31
The big one has the full old NEC logo and states Japan. The slim one has that company's characteristic old style "N" molded in its left side and states Singapore.
Here I attach their curves along the ones from a Linear Systems LSK389B that I measured for your reference. If you can't curve trace your type to compare, better use Linear Systems LSK170 or Toshiba 2SK170 matched singles that you may have if you are sure of their originality. They also work in this circuit.
The versions I have, and I have not seen any other version offered, are those two in the picture I uploaded before. See post#31
The big one has the full old NEC logo and states Japan. The slim one has that company's characteristic old style "N" molded in its left side and states Singapore.
Here I attach their curves along the ones from a Linear Systems LSK389B that I measured for your reference. If you can't curve trace your type to compare, better use Linear Systems LSK170 or Toshiba 2SK170 matched singles that you may have if you are sure of their originality. They also work in this circuit.
Attachments
I'll stick the part that I have under magnification and take a look. I notice that these have a mold mark lower front left side. My parts are slim. Thanks!
![IMG_20161019_131750[1].jpg](/community/data/attachments/536/536391-3db7fd7e3dc373c5be6988298447b474.jpg)
Nice!
So, when i was checking my layout i see that the opamp, and the relaycircuit is powered from the "left" side PSU.
So this is the way it should be right ?
Thanks and keep up
Jesper.
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Yes, 4 isolated secondaries on one transformer, gives the same isolation as two transformers with two isolated secondaries on each.
A slight advantage to using one larger size transformer is that you usually get a lower regulation. That leads to a smaller change in voltage as current demand changes.
A slight advantage to using one larger size transformer is that you usually get a lower regulation. That leads to a smaller change in voltage as current demand changes.
Great! 2sk117GR are waiting
J3 is a BF256B part. I dont think it's compatible....
Great! 2sk117GR are waiting
The original J3 (BF256B) runs 4.5-5mA with the R3 150R degeneration resistor. Its idss is averagely about double that figure. It was well steady for hot/cold arranged like that. I had twenty+ samples and all fell in the right range with that R3 value. I have tested also BF245B (discontinued) but its less predictable as it varies more for idss so it takes testing for different R3. Those are both fast RF type JFETs with good noise figures.
2SK117GR I haven't tested as J3. In any case it is not a low capacitance RF type and has more Yfs less NF. Don't know if it will behave as steady but surely it will not need some R3 because GRs have nominal idss in that area. They will need be hand picked for 4.5-5mA with 17V VDS and R3 to be a wire jumper.
Not even pin compatible. K117 need be inserted in reverse orientation and have a short for R3.
Thanks Salas, I know that I not need R3 with 2sk117gr. It happens that I have a handful of them, and I thought of using them instead going shopping. Thanks for the advice on that
Examine to know they aren't faked at least. Because Toshiba NOS parts are targets for faking.