Dear All Mikrotik Master, i've been search forum and google for this problem and no result.
Problem: no Leds on, nothing happen.
Problem cause: electric power down and when electricity on again then my RB751 non respond and all leds off
What research i do: checking power from out to inside:
-Check the adaptor (power supply) status OK, 12 volt output stable, need to check internal:
-Check first Chip Q601 (BA2T) output OK, reduced from 12 volt to 11 might be because of D2 as reverse protective that step down 0.7 volt
- Check U2 (LSP5502) output, here the problem, there is no output (only 0.1mV) checked from C50
-Continue to check U3 (LSP5502) output is 4.9 volt, status OK

Question:
1. Any one of you all master here that ever have this expirience? if any, please tell me if this is caused by the U2 failure and deen to replace or any other component? because according to the datasheet (https://datasheetspdf.com/pdf-file/7861 ... /LSP5502/1) there is other component that control the output of LSP5502 (on pin 5 there 2 resistor control the voltage output) but i see that both resistor too tiny even i cannot handle it, then if there any one have expirience please share with me.
2. If i need to recreate manually the regulator, then please inform me as reference about Voltage and the current draw, i will more research on it, it seem that the U2 chip supply for the main processor (Atheros AR7241) and i believe other component such RAM and ROM, any information on voltage and Current, because LSP5502 was able to power 2 Ampere, is that possible to replace is with 78Hxx? or just 78xx?

thank you to you who have a will to help me, thank you for your time.