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led lamp failed adapter

Discussion in 'Troubleshooting and Repair' started by pharaon, May 1, 2020.

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  1. pharaon

    pharaon

    380
    6
    Oct 28, 2014
    i have this lamp that start to dim and now no light
    so i opened it up and measure the output DC it was unstable from 4 to 16 DC Fluctuating value
    datasheet of the main ship and circuit schematic
    do you think it's the main reason? if it's and it's unavailable to get new one is there any replacement circuit i can make with available component that can give me the same output voltage?
    it light 20 LED so i guess the output volt is 72 ===> 3.6 forward volt for each led with 150 mA for the 20 led since it's all in series connection

    [​IMG]
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    [​IMG]
    [​IMG]
     
  2. Bluejets

    Bluejets

    4,857
    1,017
    Oct 5, 2014
    You should avoid playing with non isolated supplies as your schematic shows.
    There is a constant danger of mains supply appearing on the output.

    Circuit diagram does not appear to relate to your board.
    Chip likely, circuit no.

    Is this part of a totally enclosed LED bulb...???
    If so, comment at the start applies again.
     
  3. pharaon

    pharaon

    380
    6
    Oct 28, 2014
    it's
     
  4. 73's de Edd

    73's de Edd

    3,104
    1,312
    Aug 21, 2015
    Sir pharaon . . .

    Since the init is now not blowing fuses NOR has its internal FET shorted, and the unit is TRYING to work for you.
    I suspect that time, plus high frequency switching operation and developed circuit heat . . .has " BEATEN THE BRAINS " out of C1 nand C2 , see if new ones don't make the unit work for you again.

    Thasssssssssssssit . . . .


    73's de Edd . . . . .

    The problem with trouble shooting is that SOMETIMES , trouble shoots back.


    .
     
  5. pharaon

    pharaon

    380
    6
    Oct 28, 2014
    Sir 73's de Edd
    i already desoldering C1 and tested it with DMM and it gave the right capacitance
     
  6. 73's de Edd

    73's de Edd

    3,104
    1,312
    Aug 21, 2015
    i already desoldering C1 and tested it with DMM and it gave the right capacitance

    Common capacitance analysis won't be conclusive in a circuit such as those capacitors are being used in.
    Can you tell me their measured EQUIVALENT SERIES RESISTANCE values also ? . . .if not . . .sub in two new or known good capacitors.

    Also is there possibly another E- cap that is not seen here and is located on down towards the LED's ?
     
    Last edited: May 2, 2020
  7. pharaon

    pharaon

    380
    6
    Oct 28, 2014
    i don't have ESR tester
    i'll replace it with new one

    not at all
     
  8. pharaon

    pharaon

    380
    6
    Oct 28, 2014
    ok the small CAP is 1μf 50v and i found a replacement for it
    the big CAP is 6.8 μf and what i could found is 4.7μf 400v or 10μf 450v
    but couldn't find 6.8 μf
    so which would make the replacement for it
     
  9. 73's de Edd

    73's de Edd

    3,104
    1,312
    Aug 21, 2015
    10μf 450v
     
    pharaon likes this.
  10. Cirkit

    Cirkit

    135
    10
    Oct 28, 2015
    Given all the repair work and experimenting you seem to be doing, it would be a worthwhile investment. You can pick up the Mega 328 variants fairly cheaply online.
     
  11. pharaon

    pharaon

    380
    6
    Oct 28, 2014
    ok that's weird, i changed the two CAPs and tried to test the output volt , and it was the same Fluctuating value 4 to 16 DCV
    but then i said why not to test with my old analog meter ,and surprisingly it was 62 DCV steady, so i changed the 10μf 450v to the original 6.8μf 400V again, and connected the led chip and it light bright

    so i guess the wrong measurements by the DMM was cause there's no load on the circuit , is that true? if not then what would be the reason?

    not familiar with that "ATMEGA328" , what would such chip do? will i be able to have certain DCV output from it ? i read it's used for Arduino
     
  12. Martaine2005

    Martaine2005

    3,514
    952
    May 12, 2015
    Mega not Atmega. It's a cheap LCR meter.
    Some are very good. They range from about £7 - £25.
    Amazon.
    I stand corrected. The Amazon link specifies Atmega chip.
    My units are Mega clones.

    Martin
     
    Last edited: May 2, 2020
    pharaon likes this.
  13. Cirkit

    Cirkit

    135
    10
    Oct 28, 2015
    Here is another variant that has SMD test pads and connections for external probes to make it easier to test components:

    [​IMG]
     
    Allen Bong and pharaon like this.
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