A lady at work brought in a solar garden light for me to look at. The problem was that it wasn’t working. It consisted of a string of LEDs, all colored orange, just like a Xmas tree light string. On the end was a small box that fit in the palm of my hand. The top of the box was covered by a solar PV cell, and the bottom had a battery compartment cover which clipped onto the spike that held it to the ground. Under the battery cover were originally two AA cells, both NiCd rechargeables.
The garden light quit working and the lady removed the defective batteries, which were the reason that it had stopped working, and replaced them with new batteries. This was the correct solution, and would have worked if she had chosen rechargeable batteries. But instead she used regular AA cells, which were 1.5 volts each instead of 1.25 volts for rechargeables. The increase from 2.5V to 3V caused excessive current which burned out the 47 uH choke.
I removed the batteries and opened up the snap-together case, removed the screws holding the circuit board, and examined the parts and saw nothing wrong. The circuit board held just a few parts: the light green colored 47 uH choke, an unmarked IC that looked like a transistor except it had four pins, a 9013 transistor, an On/Off switch and a few other parts. Since I didn’t know anything about the four pin IC, there was no way this could be fixed if it was bad. So I used the cheapo DMM to check the choke for continuity. A choke of this value should measure from a few ohms down to a fraction of an ohm. Instead, it measured infinite resistance, or open.
Ah-HAH! I had found at least one of the problems. I unsoldered it and looked for a replacement. It had to be small because the circuit board was mounted on two posts with the components facing toward the case, and there was limited room for the part. I could not find a small choke of that value, so I got a T231212T toroid core from Surplus Sales out of a bag. I wound it with a few inches of enameled wire and measured the value, and it was 52 uH, which was close enough. I think the core had 6 turns on it. I soldered it in and crossed my fingers.
I inserted two AA rechargeable cells and turned the switch on. Well, I was pleasantly surprised when the LED lights lit up. So I reassembled the case and brought it to work.
Interesting find, I will have to remember to check thoes tiny chokes.