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LDK-100 PSU burnt resistor

LDK-100 PSU burnt resistor

LDK-100 PSU burnt resistor

(OP)
Good day,

I have on board LDK-100 PSU then suddenly telephone connected are not working. Saw on the power supply darken resistor (R49) and zener diode (D19) . Can anybody tell me what is the reason for this to get burned? And what is the real resistance of R49 and how to know it zener diode is OK because i dont have schematic diagram of this PSU. I tried putting 20ohm, 50ohm, but it is burning the resistor when cards are inserted. If i put 200ohm the power supply will not output 5 volts. Thank you for the help.

RE: LDK-100 PSU burnt resistor

I've found the problem is more the caps have gone off value. Check the tops for bulges. The resistor that usually blackens is R47 and is 20 ohms.

RE: LDK-100 PSU burnt resistor

(OP)
Mine is r49 and zener diode d19. is it also 20ohms? I check the zener diode and found its resistance is the same even wen reversed polarity on multimeter. Do you have any idea what is the voltage of this zener diode?

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