Hi everyone.
Please help me because I have a big problem.
I have several jfets like this, I need to build a simple preamp
for guitar and I don't know the correct pin arrangement.
I've tried several times but nothing sounds. Now I fear I have them
damaged all. Can you help me? Is the acronym PH Philips?
Thank you!
Please help me because I have a big problem.
I have several jfets like this, I need to build a simple preamp
for guitar and I don't know the correct pin arrangement.
I've tried several times but nothing sounds. Now I fear I have them
damaged all. Can you help me? Is the acronym PH Philips?
Thank you!
Yes, my photo is from the Philips databook SC07 Small-signal field-effect transistors from 1989.
I would expect that to be an inverting amplifying stage with quite small gain (less than 3), an output impedance of some 6 to 14 kohm and a high input impedance. Depending on the layout, it could also be an oscillator that distorts enormously when you use it as an amplifier.
What did you expect it to do and what does it do?
What did you expect it to do and what does it do?
gain is a mere 3x. you can check the fet with a mulltimeter. you should see a 0.7V diode from gate to drain and from gate to source.
when the gate is shorted to the source you can measure a resistance of about 1/idss or 160 ohms typical for a B version between drain and source
when the gate is shorted to the source you can measure a resistance of about 1/idss or 160 ohms typical for a B version between drain and source
First of al I expect it works!!! But no sound. I think values of resistor is another problem
but the first is to identify pins and i fear is impossible if connecting bad it is damaged.
i've tried in all 6 possibles variants but no sound. I'm trying simply to touch input whit a finger
and see what is in output (50hz...) but nothing. I can't destroy all jfet to find pins!!!
Sorry for my bad english...
but the first is to identify pins and i fear is impossible if connecting bad it is damaged.
i've tried in all 6 possibles variants but no sound. I'm trying simply to touch input whit a finger
and see what is in output (50hz...) but nothing. I can't destroy all jfet to find pins!!!
Sorry for my bad english...
Philips...... Nowadays - only God knows. Don't risk it, test it /BF245B/.
https://www.bestsoldering.com/how-to-test-a-jfet-transistor/
https://www.mouser.com/datasheet/2/302/BF245A-B-C_2-187308.pdf
https://www.mouser.com/datasheet/2/308/1/BF245A_D-1803072.pdf
https://media.digikey.com/pdf/Data Sheets/ON Semiconductor PDFs/BF256B.pdf
https://www.bestsoldering.com/how-to-test-a-jfet-transistor/
https://www.mouser.com/datasheet/2/302/BF245A-B-C_2-187308.pdf
https://www.mouser.com/datasheet/2/308/1/BF245A_D-1803072.pdf
https://media.digikey.com/pdf/Data Sheets/ON Semiconductor PDFs/BF256B.pdf
Do you have any information about it, like the order of magnitude of its input impedance and sensitivity?
amp is made with a old tda2003, but all these things you ask me are not really important because the pre does not play! and he doesn't even sound if I plug him into a guitar amp like a Marshall valvestate, or my gainclone hifi amp. No sound comes out of the preamp!!
The circuit is ultra-simple, and should sing whatever... Your BF245 looks suspicious: it has a PH mark, which should mean Philips, but everything is wrong: the case style, which is not TO92 PH, the fact that it is transfer-moulded which has been abandonned by Philips decades ago, the lettering/inscriptions, etc. Nothing matches, which is not to say that the FET is unoperative (dozens of second sources have appeared, and they do produce working devices, even if the original characteristics are not strictly respected).
You need to follow Marcel's advice and measure DC voltages with a multimeter: you can buy a basic model for a few $ in a thrift store, and it will be useful for many other purposes
You need to follow Marcel's advice and measure DC voltages with a multimeter: you can buy a basic model for a few $ in a thrift store, and it will be useful for many other purposes