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.

Alternate First Watt Power Supply Schematic
Alternate First Watt Power Supply Schematic
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 13th January 2019, 08:43 PM   #21
gary s is offline gary s  Australia
diyAudio Member
 
Join Date: Nov 2002
Location: Australia
As a semi retired elect engineer, one thing I have never done is mix AC mains voltage with low DC or AC voltages on any PCB, Even though Pass and others have done it in commercial designs, I would use this PCB as a CRC capacitance bank for a typical +/-25VDC power supply board only. I have some nice big fat 35mm dia snap in caps that I can use.
  Reply With Quote
Old 13th January 2019, 08:46 PM   #22
silasmellor is offline silasmellor  Denmark
diyAudio Member
 
Join Date: Nov 2016
Location: Denmark
Alternate First Watt Power Supply Schematic
I am curious about this gary, as i've wondered about that part of the design myself from looking at the commercial FW supplies. What are the issues with putting AC on the same board here? I guess the main advantage is that it looks neat. Another nice thing about the FW supplies is that wires for the rails are taken from the sides of the board, rather than the end, which often is near the AC inlet if assembling the amp in the standard modushop case...
  Reply With Quote
Old 13th January 2019, 09:12 PM   #23
gary s is offline gary s  Australia
diyAudio Member
 
Join Date: Nov 2002
Location: Australia
From my point of view, commercial designs have connections for incoming mains power wiring for several reasons - neat, saves time and cost, chassis space, drilling extra holes etc......

Provided the PCB is laid out with correct mains voltage clearances (120V or 240V) to all other lower voltage tracks then all is fine. Valve (tube) amps have this all the time if using PCB's for both AC and DC high voltage supplies.

When building amps myself either line stage or power amps, then as a matter of principle I do not run or mix low and high voltage wiring and because I do not have commercial decisions to worry about then I carefully select cable paths and run twisted pairs or shielded wiring where needed. They do not have to be separated very far apart, to have no affect on each other.
  Reply With Quote
Old 13th January 2019, 09:35 PM   #24
JeffYoung is offline JeffYoung  Ireland
diyAudio Member
 
JeffYoung's Avatar
 
Join Date: Jul 2017
Location: Ireland
Alternate First Watt Power Supply Schematic
Quote:
Originally Posted by Berny View Post
Hello Jeff, I believe there is a safety issue with your board if you intend to use mains on that PCB as is done in the FW commercial products There are regulations and you need to keep minimum distances between mains voltages and your secondary transformer voltages.... I believe it is about 5mm but am not sure. Be aware...
Hmmm... indeed. The board was designed with functional requirements rather than to meet UL certification. (From my reading of IEC60950 the "Functional" clearance for a 1,500V mains transient in a pollution class 2 environment is 0.56mm. The existing boards are 25mils/0.63mm.)

But I realise that might not make all interested folks happy, and UL certification is certainly a useful yardstick. From my reading of their requirements[1], a protective earthed pluggable consumer appliance should meet "Basic" insulation. With the same 1,500V mains transient / pollution class 2 environment that appears to net out at 2mm.

There's also "Reinforced" (which I believe is where the 5mm came from), but that's for "double-insulated" appliances with no protective earth.

Anyway, I updated the design with 2mm clearance for the "hot" nets:

Alternate First Watt Power Supply Schematic-decoupled-psu-front-jpg

Alternate First Watt Power Supply Schematic-decoupled-psu-rear-jpg

[1] https://composter.com.ua/documents/IEC60950-1.pdf
Attached Images
File Type: jpg Decoupled PSU front.jpg (228.0 KB, 618 views)
File Type: jpg Decoupled PSU rear.jpg (143.3 KB, 607 views)
  Reply With Quote
Old 13th January 2019, 09:53 PM   #25
gary s is offline gary s  Australia
diyAudio Member
 
Join Date: Nov 2002
Location: Australia
Hi Jeff,

That revision should keep others happy, how did you go with loading the board with components and checking of DC voltages?

From looking at the PCB artwork - all seems fine with it to me.

Cheers,

Gary..
  Reply With Quote
Old 14th January 2019, 12:39 PM   #26
JeffYoung is offline JeffYoung  Ireland
diyAudio Member
 
JeffYoung's Avatar
 
Join Date: Jul 2017
Location: Ireland
Alternate First Watt Power Supply Schematic
This is not my week for having my ducks in a row. The resistors labelled 3R3 on the schematic are supposed to be 0R33. (Which I fortunately noticed before soldering, but sadly not before I had ordered the wrong sized resistors.)
  Reply With Quote
Old 14th January 2019, 12:42 PM   #27
JeffYoung is offline JeffYoung  Ireland
diyAudio Member
 
JeffYoung's Avatar
 
Join Date: Jul 2017
Location: Ireland
Alternate First Watt Power Supply Schematic
Updated schematic.

Alternate First Watt Power Supply Schematic-decoupledpsuschematic-jpg
Attached Images
File Type: jpg DecoupledPSUSchematic.jpg (356.5 KB, 351 views)
  Reply With Quote
Old 14th January 2019, 09:02 PM   #28
gary s is offline gary s  Australia
diyAudio Member
 
Join Date: Nov 2002
Location: Australia
I noticed the values Jeff - these can be any value really between 0.1 ohm and 1.0 ohm, I use 0.47 ohm as I have stock of the Panasonic 3watt types. KOA Speer or Dale also have nice 2 or 3 watt resistors as well that could be used for these.
  Reply With Quote
Old 20th January 2019, 04:20 PM   #29
JeffYoung is offline JeffYoung  Ireland
diyAudio Member
 
JeffYoung's Avatar
 
Join Date: Jul 2017
Location: Ireland
Alternate First Watt Power Supply Schematic
Some pictures of the board under test.

Top trace: transformer out; each little box on the screen is 10V.
Bottom trace: cap bank out; each little box is 10mV. It's still triggering on the 50Hz from channel one, so I believe what you're seeing here is essentially the noise floor of my setup.

Alternate First Watt Power Supply Schematic-psu_xform_out-jpg

Alternate First Watt Power Supply Schematic-smooth_out-jpg

The attached .zip archive contains the Kicad board file (much easier to send a single file if your board house accepts it), and the Gerbers (a bit more work).

(The schematic is in post #27.)

Let me know how you guys get on with it.

Cheers,
Jeff.
Attached Images
File Type: jpg psu_xform_out.jpg (172.0 KB, 254 views)
File Type: jpg smooth_out.jpg (170.0 KB, 249 views)
Attached Files
File Type: zip Decoupled_Stereo_PSU.zip (131.7 KB, 29 views)
  Reply With Quote
Old 20th January 2019, 09:00 PM   #30
silasmellor is offline silasmellor  Denmark
diyAudio Member
 
Join Date: Nov 2016
Location: Denmark
Alternate First Watt Power Supply Schematic
Thanks Jeff, looking good! Nice of you to share the files
  Reply With Quote

Reply


Alternate First Watt Power Supply SchematicHide 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
FIRST WATT B4 + Linear power supply juanitox Swap Meet 6 26th December 2018 11:45 AM
Separate Power Supply for First Watt Amps Russellc Pass Labs 32 3rd September 2018 08:37 PM
looking for power supply diagram SE 813 45 Watt flyingman Tubes / Valves 1 16th February 2005 05:30 AM
55 watt Aksa boards and power supply. Tony D. Swap Meet 4 11th August 2004 07:10 AM


New To Site? Need Help?

All times are GMT. The time now is 12:36 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