Strange increase in voltage with amplifier PSU

Discussion in 'General Electronics Chat' started by Curlycat, Apr 29, 2016.

  1. Curlycat

    Thread Starter New Member

    May 2, 2015
    2
    0
    Hi guys. This is my first post here. I am busy building an audio amplifier, mostly form modules. Unfortunately ,my knowledge of electronics is very limited.

    I am running a 5A toroidal with 36-0-36 VAC into a PSU module with bridge rectifier and capacitors. (4x 10 000uf/63V) After rectification, I get 53V DC. I want to replace the PSU module with a better one (6x 10 000uf/80V) However when I use the new PSU model, I get approx 104V DC.

    I did not expect that. I thought the DC voltage would remain about the same at 53V DC? I cannot run my amp on 104V DC. The maximum I can run is 70V DC. How do I fix this and why did this happen please?
     
  2. nigelwright7557

    Senior Member

    May 10, 2008
    487
    71
    Either it is wired up wrong or you aren't measuring across the right points.
     
    Curlycat likes this.
  3. Papabravo

    Expert

    Feb 24, 2006
    10,136
    1,786
    If you go from the center tap to one of the 36VAC windings you end up with about 51 Vpeak. If you go from 36VAC winding to the other 36VAC winding you get about 101 Vpeak. Getting slightly higher DC values means your transformer is putting out more than 36VAC
     
    Curlycat likes this.
  4. Curlycat

    Thread Starter New Member

    May 2, 2015
    2
    0
    Thank you guys. I see the folly of my ways. Indeed I measured incorrectly. Last time I measured my AC voltage was also a bit higher than 220V. That would account for the 53V as appose to 51V. First picture is how I measured. Second is how I should have measured :rolleyes:

    [​IMG][​IMG][/URL][/IMG]

    [​IMG][​IMG][/URL][/IMG]

    Thanks for all the help again!
     
Loading...