No lights when powered from EXT power supply

Hi All,

Been using my Lime board for a few days - mostly powered by the USB3. RF signals through either of the 3 RF paths are quite weak.
I looked at the Quick Test procedures:

Loopback test with WCDMA has the right profile, but also a few spurs (i have LimeSDR in luftek’s enclosure+ front/rear plates). Having read in a few threads that USB power is not the cleanest one, i switched to 6V EXT power supply.
With EXT power supply i do not get any LED lights on. the board seems dead. I also used benchtop power supply (adjusting the voltage between 6V and 12V) and verified the voltage/polarity at the 6-12V socket pads - the right voltage gets there, but no current is being drawn.

I cannot see 3.3V on the FAN header and pads, neither when USB3 powers the board nor with EXT power supply.

Is my board defective ? Am i missing something here ? Any other tests i need to do (i might start looking at schematics and probing different points through power distribution)

If my Lime is defective, what is the return/replacement procedure?

Thank you.

1 Like

Sorry for a stupid question, but maybe current limit is set to less than 1A?

Check the last schematic page.Check if there is a voltage on C374 capacitor when external supply is connected. If yes, then check if there is a voltage at J21 pins 1 and 3 when external power supply is connected.

Shoot an email to Crowd Supply.

Hello Zack

Thank you for a quick reply.

Questions are never stupid…only the answers are…

I set the current limit to 2.5A on my benchtop power supply, so well within the needed power budget.

Voltage on J21 (GND and Vcc EXT) is the same as power supply. GND and Vcc INT on J21 reads about 15mV.
C374 reads a fraction of a volt lower than power supply.

IC25 is too tiny to probe at. C367 reads about 0V and so does FR56 (both ends). Does it imply IC25 is dead and therefore not powering the board from EXT power supply ?


Hello @WillWall,

Contact Crowd Supply for board replacement, please.

Hello Zack,

Sure, will do. Thank you for your time and help with the above !