B1 Help

Puffin · 18th November 2011, 10:10 AM

I am making a B1 on perfboard. I have smoked the fets. Can someone confirm the orientation. I have assumed that the schematic shows Drain to R103, Gate to R2 and Source to C101.

Zen Mod · 18th November 2011, 10:31 AM

both sources are near gate arrow - so pointing toward gnd

Puffin · 18th November 2011, 10:36 AM

Sorry don't follow. Both sources?

Zen Mod · 10:51 AM

Q100 have one , same as Q101

AndrewT · 11:16 AM

Have you measured the Idss of your jFETs? A successful Idss measurement shows that you know which legs/pins are Drains.

Since most jFETs are electrically symmetrical, you can swap drain and source and repeat the Idss measurement. This will confirm the gate pin. Now compare what you have determined with the actual manufacturer's datasheet. You should see agreement on pins locations.

I failed to follow this through when I first started with jFETs. I didn't blow any, but I got very confused by manufacturers adopting different pin outs.
To92 jFETs seem to come in every variety of pin out available.

BTW,
a 9V pp3/9 battery, a 1k0 resistor and a voltmeter virtually result in a guarantee to never damage your jFETs.

Puffin · 18th November 2011, 01:15 PM

Hi Andrew. Thanks for your reply.

I have seen the datasheet for the pin outs and have assumed that it corresponds with my fets.

What the schematic doesn't show is GDS (like a PCB mask might - but the clone boards don't!)

I will check the idss as you suggest.

Regards.

juma · 18th November 2011, 01:32 PM

Source of Q100 is connected to the Drain of Q101. Pin with the arrow is the Gate.

Puffin · 23rd November 2011, 10:40 AM

UPDATE: I now have a working board (after some "re-organization" - cough, cough....of the components) The magic smoke is still tightly enclosed.

I have no sound at the moment (apart for turn-on thump) but I am not using a pot and so need to look at the wiring again.

18th November 2011, 10:10 AM	#1
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	B1 Help I am making a B1 on perfboard. I have smoked the fets. Can someone confirm the orientation. I have assumed that the schematic shows Drain to R103, Gate to R2 and Source to C101.

18th November 2011, 10:31 AM	#2
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	both sources are near gate arrow - so pointing toward gnd __________________ my Papa is smarter than your Nelson ! tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; BAF Forum & Gallery;I'm dumb

18th November 2011, 11:11 AM	#5
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Have you measured the Idss of your jFETs? A successful Idss measurement shows that you know which legs/pins are Drains. Since most jFETs are electrically symmetrical, you can swap drain and source and repeat the Idss measurement. This will confirm the gate pin. Now compare what you have determined with the actual manufacturer's datasheet. You should see agreement on pins locations. I failed to follow this through when I first started with jFETs. I didn't blow any, but I got very confused by manufacturers adopting different pin outs. To92 jFETs seem to come in every variety of pin out available. BTW, a 9V pp3/9 battery, a 1k0 resistor and a voltmeter virtually result in a guarantee to never damage your jFETs. __________________ regards Andrew T. Last edited by AndrewT; 18th November 2011 at 11:16 AM.

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18th November 2011, 10:36 AM	#3
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	Sorry don't follow. Both sources?

18th November 2011, 01:15 PM	#6
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	Hi Andrew. Thanks for your reply. I have seen the datasheet for the pin outs and have assumed that it corresponds with my fets. What the schematic doesn't show is GDS (like a PCB mask might - but the clone boards don't!) I will check the idss as you suggest. Regards.

18th November 2011, 01:32 PM	#7
juma diyAudio Member Join Date: Nov 2005 Location: Zemun	Source of Q100 is connected to the Drain of Q101. Pin with the arrow is the Gate.

23rd November 2011, 10:40 AM	#8
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	UPDATE: I now have a working board (after some "re-organization" - cough, cough....of the components) The magic smoke is still tightly enclosed. I have no sound at the moment (apart for turn-on thump) but I am not using a pot and so need to look at the wiring again.

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