bias help
Completed a F2J using Peter Daniel boards and schematic of post 427 this thread
Transformer is 4x 20V transformer (paralleled so that I have 2x 20V) - PSU is Tea Bag board that gives me 27.5V at F2j board.
Measuring voltage before output cap I get 20V.
Lowered R4 to 1.1k and still get 20V
5k pot does not seem to have an effect.
True of both boards.
Any thoughts/suggestions would be greatly appreciated.
Thanks
Bob
Completed a F2J using Peter Daniel boards and schematic of post 427 this thread
Transformer is 4x 20V transformer (paralleled so that I have 2x 20V) - PSU is Tea Bag board that gives me 27.5V at F2j board.
Measuring voltage before output cap I get 20V.
Lowered R4 to 1.1k and still get 20V
5k pot does not seem to have an effect.
True of both boards.
Any thoughts/suggestions would be greatly appreciated.
Thanks
Bob
Thnx Zen! 
Only finding standard manual for F2 on FW site..
http://www.firstwatt.com/pdf/prod_f2_man.pdf
Manual don`t say anything about bias, or voltage..
Tried google, but no service manual..
Only finding standard manual for F2 on FW site..
http://www.firstwatt.com/pdf/prod_f2_man.pdf
Manual don`t say anything about bias, or voltage..
Tried google, but no service manual..
Ok, but that do not say how high the bias is...
Must also check over R16/R17 as Zen mentioned.
Happy New Year by the way!
Happy NY to you , too .........
didn't I replied with exact Iq value ?
in my book , that's exactly what bias means .......... except if you didn't think of bias voltage , which is completely different thing ........ and irrelevant in most cases , especially in this one
Why does it always seem like I've long missed the party?
I didn't know what other thread to try so I guess I'll try raising this one from the dead and maybe post a WTB in the swap meet.
I think the F2/F2J would actually be a better next amp project for me than the F5 I had planned. I've been playing with 8" fullrange drivers in some front horns for a while using a gainclone with them.
I tried contacting Tea Bag about JFETs/boards, but he couldn't help. I also sent a PM to Semisouth about JFETs and PM/emailed Peter Daniels about boards.
This may be something I have to try on perf board (would be a first for me). I did grab an image of Peter's board, but it is double sided with both sides in overlay. If I had seperate images for both sides I could try a transfer and etch on some double side copper clad board I have.
I wanted to ask, if one was able to locate some of the unobtainium Semisouth SJEPR100 JFETs or similar 063, are there requirements for matching or IDSS value etc?
If anyone has any boards or JFETS or a lead on either please let me know. Thanks.
Kevin
I didn't know what other thread to try so I guess I'll try raising this one from the dead and maybe post a WTB in the swap meet.
I think the F2/F2J would actually be a better next amp project for me than the F5 I had planned. I've been playing with 8" fullrange drivers in some front horns for a while using a gainclone with them.
I tried contacting Tea Bag about JFETs/boards, but he couldn't help. I also sent a PM to Semisouth about JFETs and PM/emailed Peter Daniels about boards.
This may be something I have to try on perf board (would be a first for me). I did grab an image of Peter's board, but it is double sided with both sides in overlay. If I had seperate images for both sides I could try a transfer and etch on some double side copper clad board I have.
I wanted to ask, if one was able to locate some of the unobtainium Semisouth SJEPR100 JFETs or similar 063, are there requirements for matching or IDSS value etc?
If anyone has any boards or JFETS or a lead on either please let me know. Thanks.
Kevin
this is well over 10 years ago now but it may help:
Vitalstates- Amplifiers
I may have some unused semisouths in the box as well, I will check.
Vitalstates- Amplifiers
I may have some unused semisouths in the box as well, I will check.