Welcome To the Hoffman Amplifiers Forum

September 06, 2025, 09:38:00 am
guest image
Welcome, Guest. Please login or register.
-User Name
-Password



Hoffman Amps Forum image Author Topic: PT diagram  (Read 1816 times)

0 Members and 1 Guest are viewing this topic.

Offline Nathan

  • Level 1
  • *
  • Posts: 58
Hoffman Amps Forum image
PT diagram
« on: November 21, 2023, 09:13:13 am »
Guys, I am having a brain fart and can't seem to find the info by searching...


In the diagram below, the PT should be read as 275-0-275 correct? Thus 550V secondary w. center tap?   



Then why are we getting 180V at point E? Is it because there is only half wave rectification with diodes?


FYI this is the Mesa Blue Angel power supply with solid state rectifying the preamp and tube for the power tubes... 


Thanks for your help!
« Last Edit: November 21, 2023, 09:21:22 am by Nathan »

Offline pdf64

  • Level 4
  • *****
  • Posts: 2965
Hoffman Amps Forum image
Re: PT diagram
« Reply #1 on: November 21, 2023, 09:25:17 am »
Here’s the schematic for the blue angel https://el34world.com/charts/Schematics/files/Mesa_boogie/Boogie_blueangel.pdf
Point E of the 2 schematics is totally different.
It’s 180V due to preamp current being drawn via 49k of HT dropping resistance.
At the reservoir cap it’ll be much higher.
https://www.justgiving.com/page/5-in-5-for-charlie This is my step son and his family. He is running 5 marathons in 5 days to support the research into STXBP1, the genetic condition my grandson Charlie has. Please consider supporting him! BBC News feature  https://www.bbc.co.uk/news/articles/cm26llp

Offline Nathan

  • Level 1
  • *
  • Posts: 58
Hoffman Amps Forum image
Re: PT diagram
« Reply #2 on: November 21, 2023, 09:48:44 am »
Thank you kind sir, don't know why my link to the image isn't working but you have the right one...


But my assessment is correct that it is a 550V PT?
« Last Edit: November 21, 2023, 09:53:39 am by Nathan »

Offline pdf64

  • Level 4
  • *****
  • Posts: 2965
Hoffman Amps Forum image
Re: PT diagram
« Reply #3 on: November 21, 2023, 11:17:42 am »
Yes, 550V CT = 275-0-275V.
There should be around 380V at the reservoir cap
https://www.justgiving.com/page/5-in-5-for-charlie This is my step son and his family. He is running 5 marathons in 5 days to support the research into STXBP1, the genetic condition my grandson Charlie has. Please consider supporting him! BBC News feature  https://www.bbc.co.uk/news/articles/cm26llp

 


Choose a link from the
Hoffman Amplifiers parts catalog
Mobile Device
Catalog Link
Yard Sale
Discontinued
Misc. Hardware
What's New Board Building
 Parts
Amp trim
Handles
Lamps
Diodes
Hoffman Turret
 Boards
Channel
Switching
Resistors Fender Eyelet
 Boards
Screws/Nuts
Washers
Jacks/Plugs
Connectors
Misc Eyelet
Boards
Tools
Capacitors Custom Boards
Tubes
Valves
Pots
Knobs
Fuses/Cords Chassis
Tube
Sockets
Switches Wire
Cable


Handy Links
Tube Amp Library
Tube Amp
Schematics library
Design a custom Eyelet or
Turret Board
DIY Layout Creator
File analyzer program
DIY Layout Creator
File library
Transformer Wiring
Diagrams
Hoffmanamps
Facebook page
Hoffman Amplifiers
Discount Program


password