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.

Nelson Pass A40 Help
Nelson Pass A40 Help
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 12th February 2019, 02:53 PM   #31
Robbie010 is offline Robbie010
diyAudio Member
 
Join Date: Feb 2019
Thank you everyone....... it seems that the issue here was one of confusion and tiredness, along with a pinch of lack of knowledge!

I have just spent the last 4 hours going over the original schematic and checking it against my actual circuit board and I can confirm that almost everything is in order. However, there are one or two discrepancies between the schematic (fig 6, page 4) and the representative layout (fig 10, page 6):

1. On the schematic R4 is located on the negative side of C2, but on the layout is located on the positive side.

2. On the schematic D3 is located between the emmitter of Q7 and R13, but on the layout it is located after R13.

Can anyone confirm if these observations are correct and if they are of any consequence which is the correct layout???

On another note, regarding the the use of a 10k trimpot in place of R11 & R12, I have advised the following:

"R11+R12 should *NOT* be replaced by a trimpot as that prevents the bias limiting safety circuit (D3, R13) working properly if you turn the trimpot too far.

Instead R11 should be replaced by the trimpot, wired as a variable resistor, keeping R12 as specified on the schematic.

Provided you refit R12, the trimpot's dissipation will be negligible as there should never be more than 4V across the Vbe multiplier."


Would anyone with knowledge of the circuit agree with this?

Thanks for your patience!
Attached Files
File Type: pdf Pass A40 Published Info.pdf (814.1 KB, 5 views)
  Reply With Quote
Old 12th February 2019, 02:58 PM   #32
jan.didden is offline jan.didden  Europe
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Westende Resort, BE coast
1. C2 and R4 are in series, so their order is irrelevant.

2. D3 and R13 are in series, so their order is irrelevant.

Did you make certain that the speaker return is not to the top of R22 but to ground, and that the feedback resistor is in place?

The bit above about the bias circuit is not specific to this circuit but a thoughtful way to make the bias circuit more fail-safe and should be followed, but is not required to get the amp working.

Jan
__________________
Cable: a potential source of trouble interconnecting two other potential sources of trouble - Erik Margan
Linear Audio pubs and articles . The SilentSwitcher now at diyaudio store SilentSwitcher. Keeping in touch with SY.

Last edited by jan.didden; 12th February 2019 at 03:03 PM.
  Reply With Quote
Old 12th February 2019, 03:35 PM   #33
Robbie010 is offline Robbie010
diyAudio Member
 
Join Date: Feb 2019
Quote:
Originally Posted by jan.didden View Post
1. C2 and R4 are in series, so their order is irrelevant.

2. D3 and R13 are in series, so their order is irrelevant.

Did you make certain that the speaker return is not to the top of R22 but to ground, and that the feedback resistor is in place?

The bit above about the bias circuit is not specific to this circuit but a thoughtful way to make the bias circuit more fail-safe and should be followed, but is not required to get the amp working.

Jan
Thank you Jan, yes R13 is definately present. This was my first attempt at drawing a schematic and the onset of tiredness and confusion won over in the end!!

I have ordered new trimpots and will follow the guidance as suggested.
  Reply With Quote

Reply


Nelson Pass A40 HelpHide 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
Nelson Pass Professor smith Pass Labs 79 1st August 2010 07:30 PM
FS: Nelson Pass B1 P.C.B. bchristmas Swap Meet 5 2nd June 2010 04:52 AM
To Mr. Nelson Pass lumanauw Pass Labs 39 29th February 2004 02:45 AM
My opinion on Pass Labs and Mr. Pass (Nelson) himself b_online Pass Labs 11 21st May 2003 01:39 AM
Nelson Pass at CES Nelson Pass Solid State 8 28th November 2002 08:06 PM


New To Site? Need Help?

All times are GMT. The time now is 10:31 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki