Ask about U87 Components

I'm now making EVM for U87.

Already complete of the Resistor and Ceramic Capacitor to SMD type for easy assembly by SMT process.


Anyway, I don't have any information about T1-8280800006 and LP-PCB #984908.
I saw that T1 is can replace 2N3819 but I wanna know original JFET model number.


Also, I saw that LP-PCB #984908 that on U87A schematic.


In conclusion, is this.
Q1. T1-8280800006 is can replace to 2N3819?
Q2. Can I get schematic of LP-PCB #984908?

Thanks to reading my question?

Is it your intention to commercially reproduce the U87 design?
(I get this impression because you write "SMD type for easy assembly by SMT process")

RuudNL said:

Is it your intention to commercially reproduce the U87 design?

Click to expand...

Hopefully not. Commercially producing (another) U87 via SMD would be pretty dumb at this point. There are so many other clones out there, and little or no differentiation between the cheap ones. Cheap U87 clones are a dime a dozen these days. Hopefully that's not the goal.

To answer your questions, in case others might have similar ones, the original JFET was the 2436, which is long gone, but Neumann also used the 2N3819 in production models. There's no direct SMD equivalent, but MMBF5484 should work. As always when substituting a transistor, you'll likely have to adjust the bias.

As for the "LP-PCB #984908," I'm pretty sure that's just the PCB itself.

2N5457 is a good 3819 replacement. There is an SMD version apparently.

https://www.taydaelectronics.com/mmbf5457-jfet-n-channel-amplifier-transistor-sot-23.html