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How To Service DP 30 LED Emergency Lamp

By on July 20, 2018
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This emergency light was brought to me in a dead condition. On opening the unit, I observed that the battery connections were corroded; a few components on the board had burnt.  This light uses two 4V cells, which will not have any values or ratings marked on it, except the + and – marks on the top!  Needless to say, it is a Chinese make.

One resistor was open and one transistor was found defective. Here are a few snaps:

        repairing led light

Since this is one of the products that I deal, I took a new one and opened it to see the values of the resistors.

   how to fix led light

Replaced these components and cleaned the PCB.

Connected and checked and left it for charging. It worked very well.  how to fix and repair led light

Another job added to my satisfaction list, henceforth to be referred to as ‘SL’!

This article was prepared for you by Parasuraman Subramanian from India. He is 69 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. Robert Calk Jr.

    July 21, 2018 at 7:00 am

    Good job, Parasuraman.

  2. Albert van Bemmelen

    July 21, 2018 at 3:18 pm

    Looks like a decent made emergency light. China made doesn't have to mean anything bad anymore! I recently tried to fix the backlight of a friend's Samsung UE39F5000 tv. More leds on the strips went dark after I had added brandnew 3V leds. It is a bad made product of South Korea because forums all report backlight issues with this Samsung model. There doesn't even appears to be a service manual with schematic of this tv. A tv that already was repaired in warranty time by replacing the complete backlight panel and went dark a second time after the warranty time had expired!

  3. Henrique Jorge Guimarães Ulbrich

    July 21, 2018 at 7:48 pm

    Very good, Parasuraman. I have serviced a similar emergency lamp like this. The difference was that the gadget had only one 4 V battery. The problem was with the battery itself - needed to be replaced. So I faced another problem: it was a lead-acid one. In my local market, it revealead to be a whitefly! At least in Brazil, this type of battery (4 Vcc lead-acid) is not sold! The moral of the story - in this case China imposes us to buy an "impossible to be serviced" product. A real case of programmed obsolecence. I wonder why so many emergency lamps are now in the dump due to this. Not in my case. This emergency lamp, together with a head torch that uses the same type of battery, is kept in my workshop. In due time, I´ll make provisions for them.

    • Albert van Bemmelen

      July 22, 2018 at 5:40 pm

      I wondered what type the 4V battery was. Thanks Henrique. Maybe it is a good idea to change the bad batteries by lithium cells. Just add a cheap single lithium charger/protection board and you have a 3.7V uncharged and 4.2V fully charged cell/battery! But only use the board to charge the Lithium cell (micro USB) and do not use the 5V output connection of the charher board. Only use for the 4V output to the Led board from the lithium cell + and - poles. This board with two charger indicator leds works great!:,searchweb201602_5_10152_10151_10065_10344_10068_10342_10325_10546_10343_10340_10548_10341_10696_10084_10083_10618_10304_10307_10820_10843_10059_100031_10103_10624_10623_10622_10621_10620,searchweb201603_12,ppcSwitch_4&algo_expid=9b8e4ce3-6d43-4681-a2fa-01ac9c2a4857-1&algo_pvid=9b8e4ce3-6d43-4681-a2fa-01ac9c2a4857&priceBeautifyAB=0

      • Henrique Jorge Guimarães Ulbrich

        July 23, 2018 at 9:34 pm

        Thanks for the useful information, Albert. It is really a cheap solution. I´ll consider your suggestion, and additionally, try another idea: cellphones not used anymore, not thrown away yet (what is very common) and that still have their battery in good condition. Some of them (of course I am not talking about smartphones) are small enough to be accommodated in the place left free by the defective lead-acid 4 V battery. In this case it is necessary to preserve the whole set (the cellphone with its battery) because the charging control is embedded in the cellphone). Two additional wires connect the battery to the gadget. If succeeded, I´ll have two gains: save two gadgets from the dump at the same time. All at zero cost!

  4. James

    July 22, 2018 at 6:33 pm

    Always excellent' (-_*)

    • Pasiya

      January 19, 2020 at 3:40 am

      My model is dp 7504. Now there are 2 blown reaiators in that and a faulty cap of 470microfarad. But i cant identify the blown reaistor values..i dont have another lamp to check with..please help

      • Isuru

        April 25, 2020 at 4:45 pm

        I am also having the same problem!! But my model is DP 7104

  5. Danuka Nimsara

    April 30, 2022 at 3:07 am

    How can I get the dp-7122 circuit diagram?
    Because my cercuit components are burn

  6. Tommy

    June 20, 2022 at 6:27 am

    Recently I've got a piece of this lamp DP LED714. At the plate of power supply I have found burned part signed Q2. Unfortunately marks are unreadable. Can you find the value of this component?

  7. DN Varma

    November 26, 2022 at 2:25 pm

    Thank you sir


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