Is it easy to fix digital piano capacitors?

Discussion in 'Instruments' started by Bunford, Apr 16, 2019.

  1. Bunford

    Bunford Audiosexual

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    I have a digital piano that was about £450. It's fully weighted, hammer action and pretty nice to play. However, one day it randomly stopped working. I opened it up and it looks like one capacitor has totally blown (brown ish fluff type stuff all over) and one looks swollen needing replacing too. The blown capacitor is in the power supply part of the PSU. When trying to power on now, the lights and screen flicker on, speakers pop on, but only for a millisecond before going off like it can't get enough power to start up properly.

    Is replacing these an easy job? I am normally shocking at soldering so not confident at all. However, the local repairer has said as it's a generic Chinese made model, there is no service manual nor schematic available so they can't repair it as they can't guarantee their work due to not knowing what components were in there and need replacing.

    The product seller (Gear4Music) have been quite difficult about getting it repaired. They've told me I will have to pay £10 for it to be collected, then they will investigate and give me a quote for repairing it, of they can. They will then charge for repair and charge for return postage. Therefore, just curious how much this kind of repair might cost or how difficult it it.

    On the pics, you can see the blown capacitor (silver remnants of casing) and the brown-ish fluff type stuff exploded around.

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  3. SineWave

    SineWave Audiosexual

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    Such a shame that it had blown so you don't know its specs. :( I would try searching like mad for the scheme on the net, and replace it myself. Changing capacitors is usually the easiest thing when trying to repair a piece of old gear, and especially the ones in the PSU. When the piece of gear is quite old, it's recommendable to do it as a precaution, even.
     
  4. Bunford

    Bunford Audiosexual

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    I have tried that but cannot find any schematic or service manual anywhere! It is a Gear4Music branded SDP-4 stage piano, and also mainly sold as a Medeli branded SP4000 piano. Tried searching wherever I can think of and coming up with nothing! :dunno:
     
  5. Paul Pi

    Paul Pi Rock Star

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    Gear4Music are still selling the same 'own-brand' model on their website, so they clearly have an ongoing relationship with the distributor/manufacturer. As its a generic piano they've slapped their name on, surely they should be able to request (if they don't indeed already have it somewhere) the schematic precisely for this kind of eventuality. I'd mail 'em again and press your case. After all, are they really suggesting you just chuck £450 of perfectly salvageable kit in the bin?
     
    Last edited: Apr 16, 2019
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  6. LuckySevens

    LuckySevens Platinum Record

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    Could this be the reason you blew a circuit?

    "Your order may contain items that use a 240V UK plug:
    Any electrical items in your order may have been designed to work with a 240V circuit, using a United Kingdom G type plug connection. An adapter or transformer may be required for these items to work properly and safely in your country. Some items work with a range of voltages, or have a switchable voltage control built in. Please refer to the specific product details for further information."
     
  7. LuckySevens

    LuckySevens Platinum Record

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    At this point... your keyboard is shot. If you DO want to make the repair yourself, I suggest taking the capacitor out and cleaning the area as the capacitor blew it's juice all over the other circuits and contact points. That could pose a problem in-and-of-itself when electrical current is applied to the circuit board. Then you can also clean the component and take it to some electrical supply parts store and see if they are able to determine it's capacity (and/or brand even).
    All the while being persistent with Gear4Music because after all they suggest this:

    "Gear4music products are produced ethically and responsibly to meet the expectations of a caring world.
    Questions? Email [email protected] or call 1-888-202-8188"

    If that doesn't work... I suggest blowing YOUR juice all over the capacitor and sending it to Gear4Music... then tell EVERYONE in the world about their shitty support on Facebook!!
     
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  8. GluBloB

    GluBloB Noisemaker

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    replace the "FAT" one, and the exploded with the same as C28 (look the polarity)
     
  9. OK That's a blown electrolytic capacitor. There's three ways to make that happen: too much voltage, the cap leaks and dries out or some Norbert fits it the wrong way round. My guess is too much voltage, which tends to suggest some other component has failed around the cap, and replacing it will just get you another blown electrolytic.

    This needs somebody who knows how diagnose a failed circuit. I don't think US volts over Brits explains this.

    PS I don't like the look of the solder on the LHS of the circuit board underneath. Looks like somebody's been dicking around in here before you.
     
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  10. rhythmatist

    rhythmatist Audiosexual

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    It may be easier to replace the whole power supply since you don't know why it fried in the 1st place. You can probably find a duplicate or another supply with the same in/out voltage and connectors.
     
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  11. Seedz

    Seedz Rock Star

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    Caps in Guitar amps right after the PS pop like this a fair bit.

    Normally its after a period of not being used. As someone mentioned they dry out after a period of time.........you switch em on and they do what you're looking at.

    From what I know a slightly higher capacitance than the original can (and has helped me with git amps) help stop the problem, also buying decent quality components which I doubt you have atm.

    I'd suggest that if it had been a voltage issue both caps would've popped. But you certainly need to replace both........find yourself a friendly local git amp geezer and tell him the story, he'll have come across it many times with amps and he'll be able to source and fit a decent couple of caps for ya.
     
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  12. eldarktufa

    eldarktufa Guest

    Better late than never :) This link will take you to the BadCaps forum. Very useful if any of you have this kind of capacitor problem. I've successfully repaired several motherboards with their help. Send them your pics via a post on their forum.
     
  13. Haliax

    Haliax Rock Star

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    This is your best option to protect further damage
     
  14. fiction

    fiction Rock Star

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    I've done these repairs often enough to say it's no problem to fix it yourself if you have some experience with soldering.
    You do have the specs of the cap if you can read what's printed on it and I bet you still can.
    Before unsoldering the old cap, make sure you remember the polarity... You took a pic of it, so all good.
    When mounting the new cap, make sure its voltage is at least the value as the currently used one and the capacity (given in uF) is the same.

    As for the apparently exploded one, I would have to see more details of the PCB after removing the hairs
     
  15. fiction

    fiction Rock Star

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    Possibly yes. Is that your guess or do you have more information?
     
  16. Sinus Well

    Sinus Well Rock Star

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    You don't need a Schematic. Clean the board, order the parts indicated on the board and solder them in the correct polatity. Check and adjust the incoming voltage. Done.
     
  17. Qrchack

    Qrchack Platinum Record

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    First of all, clean all the leakage right away. This stuff will corrode all metals it touches, so it's best to get rid of it as soon as possible. Electrolytic caps usually fail short (as in, act as a wire) and this means all the power is short-circuited right to ground - and never arrives to the rest of the circuitry, because it takes the shorter path instead.

    You should be able to read the markings after cleaning. Make sure to pay attention to the voltage rating written on the capacitor, you want the same or more - definitely not less. Also, if you go with a bigger rating, check the size before buying, nothing worse than getting a replacement part that's too big and won't fit.

    The flicker is likely due to the voltage ripple - it's pulsing up and down, causing the keyboard to rapidly turn on and off, never giving it enough time to fully power on. That capacitor was the part of the power supply that is supposed to filter that ripple out and give a steady voltage.

    Edit: for cleaning, ideally use isopropyl alcohol (IPA) or if you don't have it, distilled water should work. Don't use tap water and definitely no other solvents.
     
  18. fiction

    fiction Rock Star

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    Yep, good point to check the mains voltages because exploding caps are not very common except with overvoltage.
    BTW, if the little cap exploded you should still be able to find remainings of the black plastic foil somewhere inside the keyboard with the values printed on it.
     
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