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Stunning 3000A, 2000A, 3000T power supply discovery - MUST READ IF YOU HAVE ONE

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tautech:

--- Quote from: SeanB on January 31, 2024, 08:13:18 pm ---The resistors go to a trace not ground, likely with a small capacitor on the other side of the board. Higher value just means longer time to bootstrap the PSU, as most of the controller IC's will have undervolt lockout that holds them off till the capacitor charges up to a high enough voltage.

you can see the trace leading off the bottom to the daughter board, and the capacitor, and as well on the other side of the daughter board the SOT diode that feeds it in operation, with another diode isolating the feedback and power pin so the controller can sense the transformer state for feedback.

--- End quote ---
These are another common failure point in SMPS when this cap goes high ESR.

tautech:

--- Quote from: SeanB on January 31, 2024, 08:13:18 pm ---The resistors go to a trace not ground, likely with a small capacitor on the other side of the board. Higher value just means longer time to bootstrap the PSU, as most of the controller IC's will have undervolt lockout that holds them off till the capacitor charges up to a high enough voltage.

you can see the trace leading off the bottom to the daughter board, and the capacitor, and as well on the other side of the daughter board the SOT diode that feeds it in operation, with another diode isolating the feedback and power pin so the controller can sense the transformer state for feedback.

--- End quote ---
Do you know the SMPS controller pt# Sean ?

SeanB:
No, it can be any number of them, you find them almost to be generic, hundreds of part numbers, all doing roughly the same work. Same for the PFC, which will also be on this board.

mikeselectricstuff:
Four 1206 resistors fit pretty well in the original 2512 footprint

Someone:

--- Quote from: SeanB on January 31, 2024, 08:13:18 pm ---Higher value just means longer time to bootstrap the PSU, as most of the controller IC's will have undervolt lockout that holds them off till the capacitor charges up to a high enough voltage.
--- End quote ---
Put 100k parts in place of the 22k, works fine!

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