Twintex PPM-5H07 500V 0.7A DC power supply LINEAR multi stage teardown

[oz2cpu]

I did not expect to see a new cool methode of making a LINEAR dc powersupply,
no relays, no pre-regulator, just linear outputstages in series, the idea is all unused stages deliver 0V
one diode loss pr stage is all you drop,
it is a 500V unit so this makes sense, its performance is nice and stable, and quite high efficiency for a linear type,
see all technical details here :

https://youtu.be/BMRDwr5-sl4

I am not afiliated with twintex, i just scored one that is all.

[coromonadalix]

until you have a full schematic  it's pure speculation,   you need a full teardown to see more of the pcb's

you may have other things at work here without knowing it

and seeing how they "red wires" the power transistor onto the main board is a joke  ... they should be beefier, and they should not show the core like this,  poorly made

and yes  you may assume and could be right,  serial pass transistor in "serial" circuit to get to a high voltage, they use this for a long time in voltage calibrators, to get up to a 1kv

thats why you need beefier pass transistor, because they will share the same maximum current load, and the voltage thru them add's up,  but we need to know  how they switch theses pass transistors ...

this is an example of a Fluke 343A calibrator

no pun intended ... 

[oz2cpu]

I think the schematic you posted use analog mode ?
that means all series transistors share the same voltage drop ?
I also own a fluke 343A i think i recall it is 1100V at 25mA = 27 watt output
you have also seen the range switch and first voltage dial handle input voltage to serie regulator,
so the voltage drop is not too high, when only low voltage out is needed, quite smart.

what I claim this Twintex does :
they have one set of transistors made by a double pair, for better power handeling
they are the only ones in analog mode = handle the voltage regulation.
all other transistors are on/ off only, and in series, with their own bridge rectifier, also shown quite well in the video,
and when in off that stage is skipped by a reverse diode,
and when on, it simply add 100V to the input side, of the linear series regulator set.
quite smart way to avoid relay switching, so they use transistor stage switching,

sorry i dont have a schematic, hope one is leaked one day ??