So I’ve recently acquired my LimeSDR v1.4s USB-A, did all the testing as per the official information - all checked out well. I then performed the HF EasyFix1 and also a similar modification on the RX2_W following Marty’s experience.
It all worked well and the device checked out ok at this point also.
Then I went a started building my enclosure - I did some hardware work in the box itself, then I stripped the SMT mount LEDs from the device, tinned the through-holes for VCC_INT, Fan and LEDs and called it a day.
The next day I found out that my device does not enumerate in the USB devices list. After doing some preliminary measurements and consulting the schematic, I found out that my VCC3P3 power rail has failed and now measures about 0.95V. The VCC_INT rail also dropped from about 4.6V to 4.1V.
So at this point I suspect that something is loading down the 3.3 power rail, but I’ve visually inspected the board like 20 times and failed to find an obvious cause of this.
Next I’ll try to power the device externally and see what current it draws to see if it is too high or if something else has gone wrong in the voltage regulation.
In the meantime, if anyone has any advice or ideas - I’ll be most welcome. I’m prepared to fiddle around before calling the device a brick because I don’t think I’ve done anything obviously blatant.
ADDED: I tried supplying the power via the external connector. I tried voltages between 5 and 8V and it seems that the VCC_INT rail does not really change - it stays at about 4.1V. The current consumption my power supply reported was about 10mA from 7V and up, while it does not have the resolution to see what’s what on 5V.
I would like to bypass the power supply entirely and supply 4.8V directly to VCC_INT, but I’m not quite sure yet if this is a bad idea.