Solar light fault

[veedub565]

I was asked to repair a solar light for someone. Yes I know, buy a new one, but anyway.

I found that the on/off switch was corroded and intermitant,  I managed to order a replacement from China and fitted it today. However the lights now no longer turn on and off automatically, they just go on and off with the switch regardless of whether it is dark or not.

I don't get it, there isn't anything to it. A solar panel, an on/off switch, a resistor, a 4 legged package of some kind (diode pack?) 2 LED's and a battery. That's it!  I just don't get it 

Only thing I thought of was that the battery was charged with an external charger, so it's at a level beyond which the solar panel would normally charge it to, so it's not operating correctly. Running the battery down a bit may restore it's equilibrium.

[mikerj]

Is the solar panel itself working correctly, and have the devices on the PCB suffered from any corrosion?  Both faults are extremely common on the cheap solar garden lights.  The solar panel not only charges the cell, but triggers the light to switch on when it gets dark so if there's no output it will behave in the way you are seeing.

[Cyberdragon]

That "resistor" is probably an inductor. The chip is a voltage cotrolled switch with a boost converter to generate around 3V for the LEDs. Sometimes these can be messed up by too much voltage, they will sometimes dump both the solar panal and battery into the light if the battery voltage is too high (I.E. it won't turn off).

[tronde]

Some reading
https://ez.analog.com/community/university-program/blog/2014/11/14/hacking-an-led-solar-garden-light

maybe not the same IC, but probably quite similar circuit.

[veedub565]

Thanks guys

The first circuit in that link looks just like it.

As far as I can tell the solar panel is working, it used to switch on and off automatically before the on/off switch went kaput. Devices on the PCB don't look corroded.

Interesting about the boost controller becoming messed up, I'll wait and see if it starts to work all by itself once the battery runs down a bit. Although I seem to remember testing it with a 1.5v alkaline and the lights switched on and off automatically when the panel was covered/uncovered