studentkra

Hello. KiwiSDR stopped working after the thunderstorm. The power supply goes into protection. There is a short circuit on the KiwiSDR power connector.

The BeagleBone board also stopped working. Separately from the KiwiSDR, the BeagleBone shows no signs of life and the TPS65217C chip is very hot.

The problem was not only in the failed transformer T301. The 5V power line had a resistance per mass of 5 ohms. 

All linear stabilizers are out of order. Three pieces LP5907 and LMR10530Y. Moreover, the LMR10530Y was pierced through. That is, the 5V input was connected to the 1V output.

For further diagnostics, the stabilizers were replaced with similar ones.

KiwiSDR is working, but additional testing is required.

I made a short video of this repair.

https://youtu.be/6Vtmoc8Z-Eg?si=PIFDW3fEnpm8zuwE

I have three SDR receivers and a linear power supply for three channels of 5 volts. I'm using an LT1084ADJ in a TO220 package. It has been working around the clock for over a year now. And I think the LT1083/1084/1085 stabilizer is a very good and cheap choice.

Most switching power supplies change the frequency of the converter depending on the temperature. Not much, but enough to notice it at the waterfall. If it is not possible to disconnect the power source you are testing from the mains, simply heat it up a little with a hair dryer and look at the signal on the waterfall

@IK8SUT , I don't have a diagram. This is a classic power supply consisting of a step-down transformer, a diode bridge and a 1084 linear stabilizer.

I used a toroidal transformer from a BBK household amplifier. The secondary windings of this transformer had too much voltage, so I simply wound two windings on top with a thick stranded wire of 12 and 5 volts. I used four diode bridges to power three 5 volt channels and one 12 volt channel. After the diode bridges, I installed electrolytic capacitors and linear stabilizers. One 7812 and three 1084. (I bought some MP1584 high frequency converters. I'll test them for noise later). After linear converters, I used filters from inductors and capacitors. I'll attach some photos.