So, first of all HI to everyone,
second...after building the blackdog psu i'm having trouble with the preregulation, let me explain, the preregulator works but is has some problems.
by the way the linear regulator is a beast and even with all the noise that is injected by the preregulator none is seen on the output.
problems of the preregulator.
1.the transformer is buzzing like crazy because of the high current that is being drawn.
probe across 10cm of 1.75mm^2 cable in the gnd return path for measuring current drawn by the capacitors.now making some calculations wire resistance 0.96mohm(taken from a calculator on the internet). the spikes that i see are 60mV at 3.5A load.(yellow trace)
the current that the caps are drawing is 60mV/0.96mohm = 62Amps.the blue trace is the rectified voltage ..as you can see it drops quite a bit before returning up.
2.
Loading the transformer even more 9/10 amps the spikes increase to 100mV... so 100A spikes.the yellow trace also seems to flatten towards the end (the transformers cant provide the current i think?, explain this to me ).
i tried to add an inductor as people suggested in other disscussion but you need a huge inductor (photo of mine below) i don't know the inductance either.
possible solution: my transformer has a
center tapped winding 0-14-28Vac so i need a circuit that has to switch betweens the 2, if someone has an already made circuit that i could take ideas from please share it.
everything is in a drive folder i have a lot of images and the max size of the formu woudn't suffice.
note: switching preregulator are excluded because high freq noise is difficut to flatten out, maybe in a smaller bench psu i ll'try it.
https://drive.google.com/drive/folders/1aw1aTxQGjsbswE9cbhaWeTquFv80WQW1?usp=sharing