Electronics > Repair
DC Power Supply TM5020E
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Swake:
Herewith the schematic of a very similar power supply. Difference is lower voltage / amps capability but concept is the same.
MathWizard:
Yeah I don't think I've ever seen MOSFET's driven that way, and with windings, and then throw the SCR into the mix, and control loops, I bet it's a lot of work to calculate whats going on.

Ok so the secondary side windings are tied into the controller Vcc, and are being switched, and generating a little voltage and current to drive the gates I guess.
Swake:
U301 (TL494) needs some power to work (Vcc).
This Vcc power comes in on S4 in pins 3/4(GND) and 5/6(Vcc +) from H1
And now I'm lost because H1 is the output of a transformer and that can only be AC voltage.... There is no rectification unless Vcc is connected in the wrong position.
I think the schematic is also wrong or at least inaccurate in the naming of the pins GND and Vcc on S4 as it is still AC voltage.

My new question is: what voltage is coming out of H1 ?
- If there is nothing or if it is very low then the issue is 'before' T101.

MathWizard:
After looking at it again, I guess it's some type of LC resonant tank, with 2 1/2 bridges, and the gate drives being driven from the other side, and not some other source on the primary side.

But hey I got a 36V out model working, with values like I might find in a computer PSU gate drives.



I would think the H1 winding should be control Vcc for the TL494, but they do have it drawn incomplete, because pin12 is only connected to the supply cap. I would think D105 rectifies H1 for the IC, and the top of the 47uF C107 is local Vcc.
BILLPOD:

--- Quote from: Sello on December 23, 2024, 12:17:37 am ---Hi Kindly help I have a problem with my power supply doesn't show on the screen no output voltage also the fan does not run the board does not show anything burnt the components seems to be fine no shows to blown but i do not receive any voltage on the output can i get some advice on how to go about finding the fault or what may be the fault causing the power supply not to have an output.

--- End quote ---

Do they not use punctuation in South Africa??????
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