Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Pass Labs This forum is dedicated to Pass Labs discussion.

Sony Vfet Illustrated build guide
Sony Vfet Illustrated build guide
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 4th May 2019, 01:53 PM   #781
dantwomey is offline dantwomey  Canada
diyAudio Member
 
Join Date: Feb 2002
Location: Canada
Sony Vfet Illustrated build guide
Quote:
Originally Posted by Rodeodave View Post
dantwomey, V-Fets are normally open devices, which means they will conduct current from drain to source even without a voltage present at the gate. This is why the bias supply is so important, the V-Fets have to be turned off or "throttled" before the supply at T3/T5 is present, otherwise they'll burn up.

For the first startup we want the V-Fets turned off (or throttled) more than necessary, just to be safe. The 2sk82 needs a negative bias voltage, so we initially make it more negative than necessary. The 2sj28 needs a positive bias voltage, so we initially make it more positive.
Many thanks for the explanation.
  Reply With Quote
Old 5th May 2019, 09:31 AM   #782
Arye is offline Arye  Israel
diyAudio Member
 
Join Date: Jun 2003
Location: Mitzpeh Aviv
You were right, I made an error with one of R15/16 on each board, while replacing to 470R.
Now everything is by the manual.
Thanks for the attention.
  Reply With Quote
Old 5th May 2019, 02:34 PM   #783
dantwomey is offline dantwomey  Canada
diyAudio Member
 
Join Date: Feb 2002
Location: Canada
Sony Vfet Illustrated build guide
A couple suggestions that made testing quite a bit easier was the cheap multiple DMMs with alligator clips installed. And,the following test pins installed at key points on the board.

3136-3-00-15-00-00-08-0 Mill-Max Manufacturing Corp. | Connectors, Interconnects | DigiKey

Regards,
Dan
  Reply With Quote
Old 15th May 2019, 11:32 PM   #784
dantwomey is offline dantwomey  Canada
diyAudio Member
 
Join Date: Feb 2002
Location: Canada
Sony Vfet Illustrated build guide
VFETs installed and powered up on one channel. T18 to ground .008mv. DC offset at speakers terminals 17mv. R32 5mv. P1 and P2 seem to have a perfect relationship with adjusting T18 to ground.

Regards,
Dan
  Reply With Quote
Old 15th May 2019, 11:47 PM   #785
dantwomey is offline dantwomey  Canada
diyAudio Member
 
Join Date: Feb 2002
Location: Canada
Sony Vfet Illustrated build guide
Just got time today to power up one channel and tinker for a few minutes. As previously stated. P1 and P2 seem to easily zero out T18 to ground. DC offset at speakers is easily sub 50mv for now. Have not got R32 to rise yet. Still sitting near zero.

Regards,
Dan
  Reply With Quote
Old 16th May 2019, 10:14 AM   #786
dantwomey is offline dantwomey  Canada
diyAudio Member
 
Join Date: Feb 2002
Location: Canada
Sony Vfet Illustrated build guide
Another brief update. So far perfection seems to be within easy reach. P1 and P2 seem to easily balance out T18 to ground while controlling R32. It was easy (once gain) to get the desired 100mv while DC offset remains stable and low. More soon.............

Regards,
Dan
  Reply With Quote
Old 18th May 2019, 12:51 AM   #787
dantwomey is offline dantwomey  Canada
diyAudio Member
 
Join Date: Feb 2002
Location: Canada
Sony Vfet Illustrated build guide
Strange feeling when you follow the instructions and everything works out perfectly! ��
  Reply With Quote
Old 20th May 2019, 08:30 PM   #788
dantwomey is offline dantwomey  Canada
diyAudio Member
 
Join Date: Feb 2002
Location: Canada
Sony Vfet Illustrated build guide
Quote:
Originally Posted by dantwomey View Post
Strange feeling when you follow the instructions and everything works out perfectly! ��
Oooops! May have spoke too soon!

Slightly running away DC offset on one channel even though R32 is perfect and T18 to ground is under 100mv.

Questions.

Is R5(T6 and T7) and R6 (t8 and T9) supposed to be the same 1.5V after the VFETs are installed?

Regards,
Dan
  Reply With Quote
Old 20th May 2019, 09:53 PM   #789
dantwomey is offline dantwomey  Canada
diyAudio Member
 
Join Date: Feb 2002
Location: Canada
Sony Vfet Illustrated build guide
Quote:
Is R5(T6 and T7) and R6 (t8 and T9) supposed to be the same 1.5V after the VFETs are installed?
R5 and R6 were around 1.1-1.2V so with meters installed I adjusted them back up (using P3 and P4) to 1.5V while keeping an eye on T18 to ground. So far this has not helped. My DC offset keeps drifting higher. About 2-3mv per minute.

Everything else seems normal. P1 and P2 keep T18 to ground inline much the same way the first channel did.

More to come.....

Regards,
Dan
  Reply With Quote
Old 20th May 2019, 10:30 PM   #790
dantwomey is offline dantwomey  Canada
diyAudio Member
 
Join Date: Feb 2002
Location: Canada
Sony Vfet Illustrated build guide
After an hour and fully up to temperature we're at 98mv DC offset. Poor VGS matching?

Regards,
Dan
  Reply With Quote

Reply


Sony Vfet Illustrated build guideHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Aleph J illustrated build guide 6L6 Pass Labs 3645 Yesterday 06:18 PM
F5Turbo Illustrated Build Guide 6L6 Pass Labs 564 16th May 2019 02:25 PM
BA-3 Amplifier illustrated build guide 6L6 Pass Labs 224 11th May 2019 06:40 PM
F6 Illustrated Build Guide 6L6 Pass Labs 1311 4th May 2019 10:31 PM
ACA illustrated build guide 6L6 Pass Labs 157 1st February 2019 01:02 AM


New To Site? Need Help?

All times are GMT. The time now is 11:21 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki