I have bought LimeSDR from Mouser. I used it to broadcast analog television. It worked with for less than a week and then it failed. Sometimes there were “Gateware version mismatch” errors, however the firmware was up to date. Now all the LEDs are off and the computer does not see the USB device. After a week of exchanging emails Mouser support team refuses to replace it and asks me to verify that my LimeSDR is faulty on this forum. Insane, but I will do it
I have done a small research and found the following.
There is a small coil FR38 on the board. It on located in the power circuit near the USB socket and is responsible for voltage stabilization for all the board. Multimeter shows that this component has infinite resistance, but it should be near zero ohms. The voltage on it’s terminals is about 5.1 volts, but should be zero. The FR38 coil has failed. I have searched this forum and found that this is a common problem. There were LimeSDR owners who had experienced the same problem even with new and freshly unboxed LimeSDRs. I don’t know if any other components failed also, but people say that IC25 is also common issue. It’s impossible to determine it before replacing or short circuiting FR38. I will not do that to prevent any additional damage.
I have used my LimeSDR without any external power supply and with super hight quality workstation-class motherboard (assembled by Intel itself). So the motherboard should not be an issue. I haven’t measured by myself, but people on say that the current draw of the LimeSDR may be up to 1.2 amps and even more. It is likely that such a small coil can not handle so high current. The errors I had got may be also related to the faulty or insufficient FR38 coil.
From you describe it certainly seems like this shouldn’t have happened and was pretty sure we’ve only seen this before with use of an incorrect external PSU.
@Zack, anything else to suggest before we arrange an RMA?
I haven’t used external PSU. My LimeSDR was used to broadcast analog television through only one channel. Since I do not have a license for these frequencies, I used only half the transmit power. The RF receive functions were not used and the television was about a meter away. I decided that an external PSU would not be required in these conditions. Was I wrong? Is it possible that insufficient power damaged the board?
I found two cases when people faced a similar problem without an external power source.
The firmware was updated using LimeUtil as described in quick start guide and returned no errors. No settings were modified in Lime Suite GUI. Maybe these errors caused the power circuit failure?
@andrewback and @Zack, thank you for arranging RMA! Yesterday I received replacement and there are no errors or gateware version mismatch warnings as I experienced before.
Can you give us brief advice, in which conditions heat sink is recommended and when it is mandatory?
What about active cooling? When it is recommended and when it is mandatory?
In which cases external PSU is recommended and when it is required? 6-12 V, 1 A and 0.01 V RMS noise OK?
