Qnap TS 653D - no power / no light / dead

[EffiSon]

Hi,

Got a QNAP TS 653D today, which is totally dead.
After some investigation found that one of the dc-dc IC (buck converter 568215/ TPS568215) is getting too hot (with NAS own PS).
Switch to bench power supply and applied the 12V supply to identify the short circuit where found that the unit continuously draws draws 110mA !!!
Does anyone has its schematic or boardview ?

Question is how can i verify if that is the only IC which is defective ? is there any way to bypass that and verify the HW before got replacement IC ? where else can i get the similar or alternative IC ? where it is commonly used ?

Thanks in advance

[EffiSon]

Flux and remove L20. Be careful to not burn the part with the temp of the hot air tool. After the part is removed, with no power to the board and no battery, measure the resistance to ground on each PCB pad of the removed inductor.

IC U40 removed, that was shorted
Resistance at capacitor vs gnd at 1 of inductor pad is 3,5k ohm now

Which side of the removed component is showing the short condition? What is the exact resistance to ground in ohms?

No more short after ic U40 removed

Often, the next step is to use voltage injection of say 1 volt but with high current as available from the injection power supply to smoke out the shorted part. You can use IPA (alcohol) poured over parts you suspect to be shorted where the low resistance to ground will cause the part to heat up and evaporate the IPA faster than non-shorted parts.

that's my typical method too, thanks

TPS568215 is a standard part available through distribution channels such as Mouser Electronics; Digikey; Arrow.

https://www.ti.com/product/TPS568215...secase=GPN-ALT

This part has been superceded by an improved drop in replaced from Texas Instruments under part # TPS568231

https://www.ti.com/product/TPS568231

Thanks, will order sooner

Your choice to purchase either to replace this switching regulator. However, suspecting that the fault is on the consumer (downstream) side of the removed inductor @ L20 but could be the producer side (this switching regulator) who is shorted. Often are shorted capacitors.

Yes, its regulator IC, luckily no capacitors this time

12 volts onto the shorted rail? This is / was extremely dangerous to the board. Always keep the voltage injection to the lowest voltage rail on the logic board unless confirmed 100% otherwise. The reason is that this 12 volts (for your case) can reach the CPU and 100% kill the board. As a general rule, use 0v8 to 1v0.

Sorry it was my bad if i was not clear enough. I never tried to inject 12 volt on that specific section/block. Injected on the main connector to verify current consumption/short.
Since the output of the TPS568231, can reach upto max 6V as per datasheet, i wanted to try 4,5V injected to that section, but dont know about the limitations and which signals are feeding back to uC. Any suggestion

At 110mA current consumption, that is not a short. A short will peak out the max current of your injection power supply.

agreed but that what i got a constant draw

[EffiSon]

Power Inductor L20 and the output of the IC (Output vs GND) seems to be shorted but can't find anywhere else short ? is it due to IC or itself inductor which could be short ?
Nearby coupling capacitors are all OK/NOT SHORT

[mon2]

Flux and remove L20. Be careful to not burn the part with the temp of the hot air tool. After the part is removed, with no power to the board and no battery, measure the resistance to ground on each PCB pad of the removed inductor.

Which side of the removed component is showing the short condition? What is the exact resistance to ground in ohms?

Often, the next step is to use voltage injection of say 1 volt but with high current as available from the injection power supply to smoke out the shorted part. You can use IPA (alcohol) poured over parts you suspect to be shorted where the low resistance to ground will cause the part to heat up and evaporate the IPA faster than non-shorted parts.

TPS568215 is a standard part available through distribution channels such as Mouser Electronics; Digikey; Arrow.

https://www.ti.com/product/TPS568215...secase=GPN-ALT

This part has been superceded by an improved drop in replaced from Texas Instruments under part # TPS568231

https://www.ti.com/product/TPS568231

Your choice to purchase either to replace this switching regulator. However, suspecting that the fault is on the consumer (downstream) side of the removed inductor @ L20 but could be the producer side (this switching regulator) who is shorted. Often are shorted capacitors.

Switch to bench power supply and applied the 12V supply to identify the short circuit where found that the unit continuously draws draws 110mA !!!

12 volts onto the shorted rail? This is / was extremely dangerous to the board. Always keep the voltage injection to the lowest voltage rail on the logic board unless confirmed 100% otherwise. The reason is that this 12 volts (for your case) can reach the CPU and 100% kill the board. As a general rule, use 0v8 to 1v0.

At 110mA current consumption, that is not a short. A short will peak out the max current of your injection power supply.

[EffiSon]

Flux and remove L20. Be careful to not burn the part with the temp of the hot air tool. After the part is removed, with no power to the board and no battery, measure the resistance to ground on each PCB pad of the removed inductor.

IC U40 removed, that was shorted
Resistance at capacitor vs gnd at 1 of inductor pad is 3,5k ohm now

Which side of the removed component is showing the short condition? What is the exact resistance to ground in ohms?

No more short after ic U40 removed

Often, the next step is to use voltage injection of say 1 volt but with high current as available from the injection power supply to smoke out the shorted part. You can use IPA (alcohol) poured over parts you suspect to be shorted where the low resistance to ground will cause the part to heat up and evaporate the IPA faster than non-shorted parts.

that's my typical method too, thanks

TPS568215 is a standard part available through distribution channels such as Mouser Electronics; Digikey; Arrow.

https://www.ti.com/product/TPS568215...secase=GPN-ALT

This part has been superceded by an improved drop in replaced from Texas Instruments under part # TPS568231

https://www.ti.com/product/TPS568231

Thanks, will order sooner

Your choice to purchase either to replace this switching regulator. However, suspecting that the fault is on the consumer (downstream) side of the removed inductor @ L20 but could be the producer side (this switching regulator) who is shorted. Often are shorted capacitors.

Yes, its regulator IC, luckily no capacitors this time

12 volts onto the shorted rail? This is / was extremely dangerous to the board. Always keep the voltage injection to the lowest voltage rail on the logic board unless confirmed 100% otherwise. The reason is that this 12 volts (for your case) can reach the CPU and 100% kill the board. As a general rule, use 0v8 to 1v0.

Sorry it was my bad if i was not clear enough. I never tried to inject 12 volt on that specific section/block. Injected on the main connector to verify current consumption/short.
Since the output of the TPS568231, can reach upto max 6V as per datasheet, i wanted to try 4,5V injected to that section, but dont know about the limitations and which signals are feeding back to uC. Any suggestion

At 110mA current consumption, that is not a short. A short will peak out the max current of your injection power supply.

agreed but that what i got a constant draw