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.

A guide to building the Pass F4 amplifier.
A guide to building the Pass F4 amplifier.
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 15th May 2019, 10:01 PM   #1251
Mark Johnson is offline Mark Johnson  United States
diyAudio Member
 
Mark Johnson's Avatar
 
Join Date: May 2011
Location: Silicon Valley
It helped me understand the F4 circuit design better, after I drew the schematic diagram all spread apart, as shown below. In case it helps other members, here you go.

Nelson uses rail boosters in several of his amplifiers, including the "A20" Class-A DIY amplifier, published in 1974 (!). He seems to like them.

Please remember that this amplifier was designed by initials N.P. and not by initials M.J. If you want to ask "why did you do X rather than Y?" be sure to address your question to the correct person.

_
Attached Images
File Type: png First_Watt_F4_explained_r2.png (54.4 KB, 155 views)
Attached Files
File Type: asc First_Watt_F4_explained_r2.asc (7.2 KB, 13 views)

Last edited by Mark Johnson; 15th May 2019 at 10:07 PM.
  Reply With Quote
Old 15th May 2019, 11:32 PM   #1252
cal3713 is offline cal3713
diyAudio Member
 
Join Date: Mar 2014
Quote:
Originally Posted by Mark Johnson View Post
It helped me understand the F4 circuit design better, after I drew the schematic diagram all spread apart, as shown below. In case it helps other members, here you go.

Nelson uses rail boosters in several of his amplifiers, including the "A20" Class-A DIY amplifier, published in 1974 (!). He seems to like them.

Please remember that this amplifier was designed by initials N.P. and not by initials M.J. If you want to ask "why did you do X rather than Y?" be sure to address your question to the correct person.

_
Ohh yeah, I need that. Thanks.

And I replaced my burned out resistor, tried the bulb limiter and got a bright bulb. Just ordered a new board and am going to mouser to get a new set of parts. Will just build a complete replacement for that channel.

Am going to cross my fingers and hope that the mosfets and jfets can be salvaged.
  Reply With Quote
Old 16th May 2019, 12:46 AM   #1253
BigE is offline BigE  Canada
diyAudio Member
 
BigE's Avatar
 
Join Date: Aug 2008
Location: Toronto
How well matched are the mosfets? F4 manual says the MOSFETs in the first watt product are matched Vgs to 0.02v.

Also, check the f5t build thread. At the end I posted a link on how to check your MOSFETs with a dmm.
  Reply With Quote
Old 16th May 2019, 02:59 AM   #1254
cal3713 is offline cal3713
diyAudio Member
 
Join Date: Mar 2014
Quote:
Originally Posted by BigE View Post
How well matched are the mosfets? F4 manual says the MOSFETs in the first watt product are matched Vgs to 0.02v.

Also, check the f5t build thread. At the end I posted a link on how to check your MOSFETs with a dmm.
I got the MOSFETs from alweit on ebay as recommended somewhere on the thread. I'll check the numbers tomorrow and report back...
  Reply With Quote
Old 16th May 2019, 03:08 AM   #1255
6L6 is offline 6L6  United States
diyAudio Moderator
 
6L6's Avatar
 
Join Date: Oct 2010
Location: Denver, Colorado
A guide to building the Pass F4 amplifier.
Alweit is a good seller and I doubt thats the issue. I'd really like to see some good photos of the back of the PCB.
  Reply With Quote
Old 16th May 2019, 12:09 PM   #1256
BigE is offline BigE  Canada
diyAudio Member
 
BigE's Avatar
 
Join Date: Aug 2008
Location: Toronto
It's easy to check the matching. Just measure the voltages across the source resistors. They should be the same for each polarity.
  Reply With Quote
Old 16th May 2019, 01:16 PM   #1257
cal3713 is offline cal3713
diyAudio Member
 
Join Date: Mar 2014
Quote:
Originally Posted by 6L6 View Post
Alweit is a good seller and I doubt thats the issue. I'd really like to see some good photos of the back of the PCB.
Should I be soldering both sides of the PCB??

There's not really much happening back there because I soldered everything on top except the caps, the variable resisistors, the JFETS, and the shunt regulator...
Attached Images
File Type: jpg 20190507_154143.jpg (636.7 KB, 107 views)
  Reply With Quote
Old 16th May 2019, 01:17 PM   #1258
cal3713 is offline cal3713
diyAudio Member
 
Join Date: Mar 2014
I can take better photos later today after pulling the offending board... (not sure which of those above is actually the bad one)
  Reply With Quote
Old 16th May 2019, 01:56 PM   #1259
BigE is offline BigE  Canada
diyAudio Member
 
BigE's Avatar
 
Join Date: Aug 2008
Location: Toronto
It's best if the leads of the parts are soldered directly to the traces that are the circuit.
  Reply With Quote
Old 16th May 2019, 02:18 PM   #1260
6L6 is offline 6L6  United States
diyAudio Moderator
 
6L6's Avatar
 
Join Date: Oct 2010
Location: Denver, Colorado
A guide to building the Pass F4 amplifier.
Quote:
Originally Posted by cal3713 View Post
Should I be soldering both sides of the PCB??
...maybe? It depends on how good a solderer you are.

What solder are you using? Is it lead-free? Might be part of the issue.,,
  Reply With Quote

Reply


A guide to building the Pass F4 amplifier.Hide 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
An illustrated guide to building an F5 6L6 Pass Labs 1185 4th April 2019 03:42 AM
A Concise Guide to the Published Amplifier Circuits of Nelson Pass rsdio Pass Labs 55 6th November 2018 05:40 PM
My,PASS ALEPH J and f4 xr000 Pass Labs 1 25th December 2009 03:20 AM
Idiotīs guide to building Pass amps? judge Pass Labs 3 19th December 2004 11:33 PM


New To Site? Need Help?

All times are GMT. The time now is 11:23 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