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Capacitor Help

Discussion in 'Power Electronics' started by Reddave101, Mar 10, 2020.

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  1. Reddave101

    Reddave101

    14
    0
    Mar 10, 2020
    Hi all, hope I’ve posted this in the correct place, I’m having a problem with an old AIWA separates stereo,. The whole thing powers on and plays but the love screen on the map and the radio went blank but. Still worked perfectly, I removed the top of the map and saw a capacitor had blown which was a 100uf 10v. I’ve replaced it, and everything light up perfect again but after 5 mins the screens were dimming, so I took the lid of the amp again and the same capacitor was half way blown again, so I put yet another new one in and after 5 mins it did the same again, any suggestions what I’m missing would be greatly appreciated as love this stereo and just want it up and running perfect again, any help reallly appreciated
     
  2. bertus

    bertus Moderator

    1,002
    371
    Nov 8, 2019
    Hello,

    Did you place the capacitor the correct way around?
    Electrolytic capacitors are polarity sensitive.
    When it is mounted the wrong way around, it is prone to fail again.

    Bertus
     
  3. Reddave101

    Reddave101

    14
    0
    Mar 10, 2020
    Thanks for the reply, yes put the correct way round, the third one I thought maybe I was looking at it wrong and put it the opposite way round and that one lasted about 30 seconds, have checked voltage from the main power supply and all is correct according to the service manual, I’m thinking possibly putting a higher voltage capacitor in but unsure as if too much voltage is getting through which is causing it to pop it may pass more through and pop something else, thanks again
     
  4. bertus

    bertus Moderator

    1,002
    371
    Nov 8, 2019
    Hello,

    Is there a link to the service manual or schematics of the unit?
    That way we could look, by the hand of the schematic, what is happening.

    Bertus
     
    Cannonball likes this.
  5. Reddave101

    Reddave101

    14
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    Mar 10, 2020
  6. Reddave101

    Reddave101

    14
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    Mar 10, 2020
    BCE9EAEF-AB08-48A9-9D57-FE2C7DDA4E56.png 2BB0FD79-3D9E-46B9-876D-26436C48C7D2.png 963C1DF8-A155-4046-A251-63456B9CAE01.png 11104B35-FA01-474B-B002-A38B6E743BC6.png
     
  7. Reddave101

    Reddave101

    14
    0
    Mar 10, 2020
  8. bertus

    bertus Moderator

    1,002
    371
    Nov 8, 2019
    Hello,

    That is strange. In the shown table, C114 is 100 uF, in the schematic it shows as 470 uF:

    Aiwa_power supply part c114.png

    Looking at that part of the schematic, less than a volt is accross the capacitor.
    Could it be that transistor Q111 has failed, having much more voltage accross the capacitor?

    Bertus
     
    duke37 likes this.
  9. Reddave101

    Reddave101

    14
    0
    Mar 10, 2020
    Thanks for that I never actually noticed the difference in the parts list and the drawing, I’m going to test the transistor to check voltage but will also stick a 470-10 in as well, really do appreciate the help, will check in the morning and will get back to you
     
  10. Ylli

    Ylli

    336
    91
    Jun 19, 2018
    While you are there, also check and confirm R104 is actually 10 ohms, and has not gone high.
     
    bertus likes this.
  11. Reddave101

    Reddave101

    14
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    Mar 10, 2020
    Just a quick question, I’ve only got a 470-16 in my box, I know the 16v won’t be a problem but just say the drawing is wrong, putting a higher capacitance in it won’t cause an issue will it?? As in mushroom cloud? Thanks again
     
  12. Reddave101

    Reddave101

    14
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    Mar 10, 2020
    Just an update, I only had 3 100-10 capacitors left in my box so I ordered more yesterday. They have just arrived and they are slightly different, they are 100-10 but these are bigger and exact model the manual says to use, which are the 5x11. So they are double the size of the ones I did use, I know 100-10 is 100-10 regardless but wondering if the size does matter(so I’m told lol), will post outcome shortly and hopefully won’t try the other ones(470) and no chance of mushroom cloud and whole in the earth
     
  13. Reddave101

    Reddave101

    14
    0
    Mar 10, 2020
    Well I’ve installed the new capacitor, has lasted a bit longer but the two screens are off again, so my previous question still stands if anyone knows please? If I follow the drawing and put in a 470uf 16v will it blow up if the drawing is wrong and it should only be 100uf? Thanks again for all the info
     
  14. Tha fios agaibh

    Tha fios agaibh

    2,107
    708
    Aug 11, 2014
    I would trust the components you have over what the manual says.
    You may have a revision of original circuit.

    Size shouldn't matter as long as it physically fits.

    I'd also check zener D105.
     
  15. Reddave101

    Reddave101

    14
    0
    Mar 10, 2020
    Yet another update, had a thought after I replaced the capacitor again with the same ones 100-10, why is just the amp and radio screens going off, so disconnected the radio from it and everything worked perfect, as soon as I plugged radio back into it, it started fading again until capacitor popped so now I’m going down the route of the radio, have stripped it down and all capacitors look ok so going to test all the board as think it may be the radio at fault
     
  16. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,412
    2,779
    Jan 21, 2010
    Get a 100uF 63V cap, install it, and measure the voltage across it.
     
  17. bertus

    bertus Moderator

    1,002
    371
    Nov 8, 2019
    Hello,

    Did you check R104 and Q111 ?
    It looks like the voltage on the capacitor is to high due to failing parts.

    Bertus
     
  18. Reddave101

    Reddave101

    14
    0
    Mar 10, 2020
    Hi again thanks for all the reply’s and help, I’ve found the original cap hiding under the board and it is a 100-10, so that is correct, it’s still popping after a few minutes so definitely something else is overloading it. Is it possible to change it for one with a higher uf and voltage? As said before could I use a 470uf 16v?
     
  19. Reddave101

    Reddave101

    14
    0
    Mar 10, 2020
    Or even a lower uf as also have a 22uf 50v?
     
  20. Reddave101

    Reddave101

    14
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    Mar 10, 2020
    Sorry forgot to mention R104 has possibly failed as tested the 100-10 and its testing as 47.4v is going through it hence the pop
     
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