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Servicing Collapsible Solar Lantern

By on July 11, 2017
how to fix solar lantern











repair solar lantern

We, the electronic technicians, especially the hobbyists, are a good contributor for preventing electronic waste and are doing a commendable service to the mankind! If we are not there, the number of sets that would have become electronic waste is unimaginable, disposal of which is always a headache for the individuals and/or concerned authorities! Here is another story of rescuing a lamp from this dump!

This is an advanced collapsible lantern, which can be charged on solar power as well as mains and is one of the products that I deal with. One of my customers brought this back saying that it is dead, after using it for many months. I twisted and pulled out the top cover and found that water had gone in, as a result of which board and battery had got shorted, leaked and the acid and water had peeped deep inside. Now, handling this is a risky thing, as it can burn the skin and spoil the tools used, as battery acid will eat its surface! This was a new challenge to me!

Even the gloves we wear can get damaged!  I thought for a few minutes how to deal with it and struck with an idea. Sprayed IPA liberally, simultaneously wiping and cleaning the area with a cotton cloth.   Repeated this a few times. Since the soldering on the PCB had become almost like cast iron, removed the wires shaking and pulling. I repeated the process until all the top parts were removed, wherever I could see acid leak. The acid had already damaged the reflector of the lamp partially. Completely dismantled the set:

 fix solar lantern

This lamp is assembled this way:  The top cover holds the battery and has the solar panel on top of it.   The next portion holds the USB port (for charging mobile from it) and Power Inlet, and has the stainless steel holding brackets on both sides. A long screw goes from this to the bottom for holding the lamp portion tight, as this part moves up and down for drawing out to switch the lamp on and push it in to put it off. Once we remove the screw, we can remove that portion and can see an LED Holder, with holes in the centre as well as the positions where the LEDs are fixed on the round PCB.

Then a white dome fixed upside down, which provides a bright and evenly spread cool light.  The transparent acrylic cover not only holds both the top and bottom portions like in a drum, but also serves as a protector.  The next portion is the one which has a hollow tube in the centre, through which the wires from the bottom portion (from on/off switch and support battery terminals) run. This has two projections at both sides, covered by rubber sleeve and this is the portion that slides through groove provided on the outer black cover. At the round bottom of it, there is a spring fixed on one side to press the switch off when lamp is collapsed and release it when pulled up. The next part is the nut covered by a half bracket to allow wires to run through to the top, to tighten the screw from the top for holding the moving part tight. The next portion is fixed with four screws to the black outer cover, which houses the four additional batteries for extended use in any camp. The bottom cover can be twisted for removal. In some lamps this is screw type. Now, just see the pictures, in the same sequence for visual explanation:

             how to repair solar lantern


The work that I did on this: After thorough cleaning, checked and found that all the 6 LEDs were short and the board itself cannot be reused. So took a similar 6 LED board, dimension of which was more.

solar led

Kept the old LED Board on top of this, marked the diameter, then cut the extra piece. This was possible as the extra piece had only a portion of the negative track. Increased the hole in the centre to match the old LED board. Drilled two holes like in the old board for inserting the board on two stubs provided for it in the housing. Ensured that all the LEDs are properly aligned to fit into the holes provided in the LED board housing holder. Inserted the wires from bottom and soldered the white wire to negative of the LED and soldered a Red wire on its positive.

Brought this red wire along with the yellow and another red wire from the bottom through the centre hole. Inserted the screw from the top and placed its nut at the bottom and after ensuring that the wires are not jammed in any of these and are routed freely on the sides, slightly tightened the screw for just holding it. Cleaned and scraped the joints in the main PCB to remove acid damages and retouched all points using flux. Then soldered all the wires to the main PCB at the marked places.   Soldered the AC in wires, solar power in wires and finally inserted the battery on its place and soldered these two wires on the PCB. The PCB has markings on it for connections:

solar led repair

Completed the assembly of the lamp as described above and checked the lamp on/off when pulled and pushed in, charging by AC Power and charging by solar power. See pictures below:

how to fix solar lantern

Thus, this lovely lamp was saved from dump!

This article was prepared for you by Parasuraman Subramanian from India. He is 68 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done  graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.

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You may check on his previous repair article below:




  1. parashu ram singh

    July 11, 2017 at 1:28 pm

    wonderful knowledge got to see the such lamp i have never ever seen
    before thanks many many for giving such information and hope you send me again for such type intimation/information.

  2. Albert van Bemmelen

    July 11, 2017 at 3:47 pm

    You've really exceeded yourself, and again, in taking the time to repair someone's quite unique device Parasuraman! Especially in the cleaning with IPA part (don't think we have or know that product over here). And the reconstruction of the ledboard by replacing it with another one making it fit. Although you took enough photos and tried to explain it with understandable text, I probably still have to see such a lantern myself to fully understand its construction.
    After reading about all 6 leds short circuiting I take it that you had checked all of them seperately. Because they likely were connected in parallel.
    According to the text on the 6 led board they were because of the 4V description. Also because the 3 rechargeable battery holder pack makes 1.2V x 3 which is with 3.6V enough for all 6 leds to operate in parallel at a constant voltage and at a safe current. And I guess that the board was not to be reused because of the bad tracks, and not because of short circuiting which you probably had checked too.
    Its a shame that you left out taking a close up view from the controller/driver board of this Solar Lamp. I would have liked to know what components were used. Or a little circuit of the lamp would have been nice. (You probably left that part out because of copyright reasons?). And I wonder if you were able to somehow make sure that rain or moisture couldn't penetrate the circuitboards next time? Because it would be a real shame if you had to do this timeconsuming and very successful repair all over again.

    • Parasuraman S

      July 12, 2017 at 8:47 pm

      Many thanks for your detailed observations and suggestions. The LEDs and board were all bad spoiled by the battery acid. IPA stands for isopropyl alcohol. I indeed took a close shot of the board from the components, but while transferring it from mobile to computer, it was missed and I have no clue why. Since these are old, I could not locate it again in my mobile and probably it could have got erased when I purge all unwanted images from the storage. The circuit is very simple, like any chinese lamp. 230V AC is directly fed to the board, one side through a capacitor dropping the voltage to the required limit. Both these AC inputs (one direct and another through this capacitor, are fed to bridge rectifier, and smoothed by a 47mfd/25V capacitor. A 1k resistor is used to control current and voltage to the LED. The battery is directly connected to the +/-, the LEDs via the on off switch at the bottom. The solar input is fed, - directly and the + through IN4007 diode. This is to enable charging depending on the potential. USB charger is wired from the battery directly. There is nothing complicated in this circuit. There is no over voltage protection, battery charge limiter or any such thing! There is a charge dropping resistor of high value (I think it was some 470K) connected across the Fixed Capacitor used for dropping AC input. I think it was a 1.5mfd Fixed Capacitor. That is all! As for the water seepage inside, I had cautioned the customer about what had spoiled the lamp and asked them not to keep near windows (which was the cause for rain water seeping in) for two reasons (1) over charging from direct sun light and (2) Water seepage. I did not cover the sides as there are small holes there for ventilation and battery fumes to go out.

      • Albert van Bemmelen

        July 15, 2017 at 3:29 am

        No problem Parasuraman, I understand the electronic circuit now. Thank you for the clear explanation. I hope that no one is able to touch any of the wires inside or the circuit while charging it on 230VAC. Or takes out or puts in any of the rechargeable batteries which could be fatal of course!
        The resistor over the Capacitor of 1.5uF (and not miliFarad.. which would make the Xc resistance with a value of only 1/(2xPixfxC) = 2.12 Ohm much too low instead of 2.122 Kohm) is of course for discharging any high voltage charge that it still contains after disconnecting the lamp from the AC main power. I think it probably also has some kind of switch to disable the 230V AC when the USB charger connection is used (or is there only a warning on the outside of the lamp written?). And it should have a primary Fuse too to prevent causing any fire.
        To prevent any oxidation on components and wires I used clear varnish to protect the inside electronic circuit of my Solar lamps. Also on the ordinary two legged white leds in my solar lamps because the legs were mostly badly damaged and couldn't be soldered afterwards. Cheers!

        • Parasuraman S

          July 16, 2017 at 7:37 pm

          1) Caution is already there in the manual that accompanies it. 2) Yes, it is uF value. 3) Yes, resistor is for discharging residual charge. 3) Nothing! USB is not isolated! That is the funny thing in this! 4) No primary fuse either! Many thanks!

  3. Yogesh Panchal

    July 11, 2017 at 9:51 pm

    Good job! Sir.

  4. Robert Calk

    July 13, 2017 at 2:37 pm

    Good job, Parasuraman. I'm glad you could save the lantern from the trash.

  5. Geoffrey Wight

    July 13, 2017 at 7:49 pm


    Really enjoy the thoroughness that you approach your projects with,  it's like a scientist looking into the unknown, or a doctor looking for a cure!  A sure path to success.  It is satisfying to resurrect a device headed for the void. Job well done.

  6. Humberto

    July 19, 2017 at 12:07 pm

    Good repair, thanks.

  7. charles

    July 19, 2017 at 3:24 pm

    Thank you for detailed write up it is assisting us junior technicians to become experts.


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