I bought this Radio kit as a present, but I soon got news that something bad went on during power up. There was some heat involved, plastic smell and breadboard deformation! And that the radio doesn’t work ..
Curious, I asked it back, maybe I can have a go at fixing it.
Things weren’t looking good indeed, the breadboard was melted:
I checked for shorts but the breadboard was still fine.
Injecting audio into the amplifier also proved that amplifier part was still working. Which was amazing given how melted the board was! But assembled, the Radio would just hiss and not finding any stations.
It was looking more and more that the problem was with the FM Board:
The instruction booklet presents the voltages on the J1 pins, and surprise, the third pin from the left is supposed to be 3V, but it measured ~1.7V. Also, no detectable current draw. I repeated the measurement on a known good protoboard, but it behaved the same:
The small 3 pin component looked like a voltage regulator and was marked HT30. Only reference to it that I could find was on Aliexpress – from where I could (and did) order 20 pieces for 1.98 euros:
It was challenging to do a good job using a normal soldering iron, but I got it:
Upon power up, things were looking much better – the 3V were there and the board was now drawing about 14mA (on my crude power supply):
It was time to remount the FM board onto the original breadboard and give it a try 🙂
In conclusion, this is a nice kit – and most likely what happened was swapped battery polarity during the initial assembly. Although I don’t really know.
Many things crossed my mind. The FM circuit is a CL6017S and it can be bought and replaced if needed. The micro-controller (PGS134) is also available to buy, but I could not find the source code. And even if I could, I don’t have a way to program such controller. If any of the ICs would be shorted (and would pull down the output of the voltage regulator), there should have been some detectable current draw. Thus, the most likely culprit was the regulator itself. Thankfully, it behaved fine and protected the other components.
What is nice about this FM Radio kit it receives very cleanly, and you don’t necessarily need use all components to listen to FM. If you just want to scan, the push-buttons are not needed for example.
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