2nd Gen FET question (Solved)
Moderators: pompeiisneaks, Colossal
-
- Posts: 451
- Joined: Tue Sep 04, 2007 9:32 pm
- Location: UK
2nd Gen FET question (Solved)
Inspired by the tones that Erwin and others are getting using the FET boost, I've decided to revisit my 2ND Gen and get the FET working properly.
My 2N3823 has 4 pins, but the layout/3rd Gen schem is wired with 3 pins. I realize that one of the pins is the case, but what needs to be done with this leg for it to operate correctly?
If anyone can help, it would be greatly appreciated.
Cheers,
Paul.
My 2N3823 has 4 pins, but the layout/3rd Gen schem is wired with 3 pins. I realize that one of the pins is the case, but what needs to be done with this leg for it to operate correctly?
If anyone can help, it would be greatly appreciated.
Cheers,
Paul.
You do not have the required permissions to view the files attached to this post.
Last edited by Guitarman18 on Tue Jul 04, 2017 9:12 pm, edited 1 time in total.
'Beauty is in the ear of the beholder'
-
- Posts: 213
- Joined: Sun Feb 02, 2014 6:13 pm
Re: 2nd Gen FET question
ground the case
-
- Posts: 213
- Joined: Sun Feb 02, 2014 6:13 pm
Re: 2nd Gen FET question
http://ampgarage.com/forum/download/fil ... &mode=view
I like this particular layout for reference, it is clear to read and works like a charm.
I like this particular layout for reference, it is clear to read and works like a charm.
- martin manning
- Posts: 13162
- Joined: Sun Jul 06, 2008 12:43 am
- Location: 39°06' N 84°30' W
Re: 2nd Gen FET question
It might work fine with just GDS connected, but run the case lead to ground. I noticed the 2nd gen layout is missing an eyelet-eyelet connection and a ground. You might have to adjust the voltage divider and the source resistor to get the right bias point. See in the files section for a sticky on that.
You do not have the required permissions to view the files attached to this post.
-
- Posts: 451
- Joined: Tue Sep 04, 2007 9:32 pm
- Location: UK
Re: 2nd Gen FET question
Excellent info davebolden44 and Martin.
Many thanks for that. I'll get on to it as soon as I can, and report back.
Best wishes,
Paul.
Many thanks for that. I'll get on to it as soon as I can, and report back.
Best wishes,
Paul.
'Beauty is in the ear of the beholder'
- norburybrook
- Posts: 3290
- Joined: Mon Jan 06, 2014 12:47 am
- Location: London
- Contact:
Re: 2nd Gen FET question
what are people using for the JFET these days the NTE452 is now obsolete.
I've got a FET board laying around I might add one to my #102.
Marcus
I've got a FET board laying around I might add one to my #102.
Marcus
- erwin_ve
- Posts: 1707
- Joined: Fri Jan 25, 2008 8:06 am
- Location: Dordrecht, Netherlands
- Contact:
1 others liked this
Re: 2nd Gen FET question
I used 2N4416A. You can get them at mouser.
-
- Posts: 213
- Joined: Sun Feb 02, 2014 6:13 pm
Re: 2nd Gen FET question
Its not like you cant get the nte452. I bought several recently, cant remember where. Maybe amazon
-
- Posts: 451
- Joined: Tue Sep 04, 2007 9:32 pm
- Location: UK
Re: 2nd Gen FET question
Hi Marcus,
I used these 2N3823;
http://www.ebay.co.uk/itm/112032431092
Having said that, I still haven't managed to get my FET board to come to life. Either the FET is not working or something else is a bit dodgey.
I'm going to completely rebuild the FET board tomorrow and find out if that helps. Dammit!
Cheers,
Paul.
I used these 2N3823;
http://www.ebay.co.uk/itm/112032431092
Having said that, I still haven't managed to get my FET board to come to life. Either the FET is not working or something else is a bit dodgey.
I'm going to completely rebuild the FET board tomorrow and find out if that helps. Dammit!
Cheers,
Paul.
'Beauty is in the ear of the beholder'
- martin manning
- Posts: 13162
- Joined: Sun Jul 06, 2008 12:43 am
- Location: 39°06' N 84°30' W
Re: 2nd Gen FET question
You can disconnect the power lead and then use the battery method to power it and see if you have an appropriate value for the bias resistor. Even if there are no wiring errors, the FET must be biased correctly. I bought a bag of ten 2N3823's not too long ago from a parts dealer, and 2N4416A's are readily available (somewhat pricy, though).
Re: 2nd Gen FET question
What's a good B+ level for checking the FET board separately before installing it into an amp?
-
- Posts: 451
- Joined: Tue Sep 04, 2007 9:32 pm
- Location: UK
Re: 2nd Gen FET question
Thanks Martin,martin manning wrote: ↑Mon Jul 03, 2017 7:42 pm You can disconnect the power lead and then use the battery method to power it and see if you have an appropriate value for the bias resistor. Even if there are no wiring errors, the FET must be biased correctly. I bought a bag of ten 2N3823's not too long ago from a parts dealer, and 2N4416A's are readily available (somewhat pricy, though).
I've used your 'Method to Set Fet bias and Supply voltage' before, which was very helpful. I'll revisit that for this FET board, but I think it may be more than a bias issue. I also tried dropping the 3.3M to 2M, as per Gary's suggestion 'if your FET isn't passing gas'.......
Cheers,
Paul.
'Beauty is in the ear of the beholder'
Re: 2nd Gen FET question
Thank you sir.
-
- Posts: 451
- Joined: Tue Sep 04, 2007 9:32 pm
- Location: UK
Re: 2nd Gen FET question
The setup I have at the moment looks like this;
If anyone can see anything wrong with this picture, I'd really appreciate it. It will save me from starting a new board.
Thanks in advance for your help.
Cheers,
Paul.
If anyone can see anything wrong with this picture, I'd really appreciate it. It will save me from starting a new board.
Thanks in advance for your help.
Cheers,
Paul.
You do not have the required permissions to view the files attached to this post.
'Beauty is in the ear of the beholder'