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Casio WK-3000 no power on adapter but power on batteries

Discussion in 'Troubleshooting and Repair' started by Jimkarl, Sep 15, 2017.

  1. Jimkarl

    Jimkarl

    43
    2
    Aug 23, 2014
    Have this keyboard with a tested good DC adapter but will not power up (unless running on batteries. Adapter is a 12V negative tip as required. Was concerned the DC power socket was not making contact consistent contact so replaced that.. See attached circuit diagrams. On diagram 1, I see 12 Volts at the jack now, 12V past L202 (pins 1&3). But I only see 1/2 volt at pins 8/9 of the connector to the next board. Tracing that back to D202, again i only see 1/2 volt there as well. Swapped that out for new diode - no change. I have to assume something on the second board (see diagram 2) is shorting/drawing power down, but not when batteries are connected. Thoughts what to check?
     

    Attached Files:

  2. kellys_eye

    kellys_eye

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    Jun 25, 2010
    Where are you putting your meter leads to make these measurements?
     
  3. Jimkarl

    Jimkarl

    43
    2
    Aug 23, 2014
    Didn't I say all that? Maybe not clearly. L202 pins 4&6, L202 pins 1&3, pins 8 & 9 of the board connector (J3G),
     
  4. davenn

    davenn Moderator

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    Sep 5, 2009
    if you leave the neg (blk) lead of your meter on L202 pin 3 or 4 and then move your red meter lead to pin 9 of the interboard connector, you should see + 12V

    I'm not really sure of the purpose of D202 ?

    do you have a link to the full manual please ?
    It may help to see where these power lines are going to.

    your first image starts to show the battery but we don't see how it is connected


    Dave
     
  5. Jimkarl

    Jimkarl

    43
    2
    Aug 23, 2014
    Service Manual uploaded to my google drive here https://drive.google.com/file/d/0B_Yuh1ijNVjmZU42cGlKaXRQYnc/view?usp=sharing
    I showed the battery connection on the second image in red (it connected off the screen view but to those same two lines) but in any case you'll see it clearer in the full manual.
    I do get 12V when measuring there - but I was expecting 12v when measuring between 8&9 on the interconnect. Perhaps that is incorrect. I assumed that because if you follow that interconnect to the next board (diagram 2) it connects to the same point the battery does (albeit with a fuse and diode inbetween)
     
    davenn likes this.
  6. dorke

    dorke

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    664
    Jun 20, 2015
    Please measure the voltage on D202.
    You should get about 0.5V,anode=pin2 (+).

    Just to be on the safe side,
    You should get 12vDC on L202 between pins 1(+) and 3(-)

    Dave,
    D202 is a series blocking diode to prevent reverse polarity connection of external DC adapter.
     
  7. Jimkarl

    Jimkarl

    43
    2
    Aug 23, 2014
    yes 12V on L202 between 1 & 3.
    Not clear on your 0.5V location reference above "anode=pin2(+)", but I did get 0.5v between L202/Pin1 & Anode D202.
     
  8. dorke

    dorke

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    664
    Jun 20, 2015
    Like so:

    Noname.jpg
     
  9. Jimkarl

    Jimkarl

    43
    2
    Aug 23, 2014
    I get 12v across the diode, not 0.5v
     
  10. dorke

    dorke

    2,342
    664
    Jun 20, 2015
    If you get 12v across the diode with the marked polarity ,anode positive.
    Then you have a faulty diode(open).
    Lift one leg, and check to verify it is faulty in diode test mode of your DMM.
     
  11. Jimkarl

    Jimkarl

    43
    2
    Aug 23, 2014
    OK so this is weird. I replaced that diode previously when I first started. the diode I pulled out was seeing about .1v in Diode mode whereas the one I put in was about .151v. I thought that was a weird reading (I was expecting .5 or .6v) , but all the diodes in the package read the same, so I assumed it must be the type of diode and that was normal. Can't believe a whole new pack of 20 diodes are all bad right?

    Now just pulled out the fresh one I had put in earlier - now reads .1v as well. Put another in, reads .561v before. Apply power, check the voltage across the diode. Still 12V. Pull the diode, now reading .1v in diode mode. Something is killing the diodes after they are in.

    3am here so i'm going to hit it and will try any further suggestion/measurements tomorrow. Thanks for the help thus far!
     
  12. dorke

    dorke

    2,342
    664
    Jun 20, 2015
    Fisrt thing,
    Did you buy the diodes on Ebay or another Chinese source?
    If you did,don't rule out the possibility that you got fakes.

    Second,
    with the diode out and no power or batteries,
    measure the resistance you see at the adapter input and between pins 9 and 9 of JG3.
    In both cases switch the DMM polarity and test the same in Diode test mode as well.

    third,
    You mentioned replacing the adapter connector,
    Please recheck your work at that.
    Are the 2 connectors identical?
     
  13. davenn

    davenn Moderator

    13,315
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    Sep 5, 2009
    That was the only thing I could think of also
     
  14. 73's de Edd

    73's de Edd

    2,726
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    Aug 21, 2015
    Sir Jimkarl . . . . .

    IF the WK-3700 is schematically being the same as the WK-3000 here is a simplified and dedicated schematic, that is showing solely your power flow in both battery and external power connections.
    In order not to have to use an internal / external power changeover switch they have used two power steering diodes for isolation and routing, to automatically let you revert between a use of a power pack or the internal batteries.

    Consulting the referencing:

    If you can turn the unit on and off with internal battery power . . .all is well up to my marked in RED A and BLACK B markers.
    Now take DC voltage metering leads up to my marked in RED A Prime ad BLACK B Prime markers. If the voltage read out there is the same as the voltage read out back at RED A and BLACK B markers, all is being well up to that point.
    You then just have to pull one cell, to drop battery power, and ohm out from the RED A Prime marker to the end of the connecter . . . .note that the plug entry switch is non functional / by virtue of being continually shorted.
    That will have tested the POSITIVE power leg.
    Ohm out between the cathode of D202 to the ground collar of J201.
    That will have tested the NEGATIVE power leg.
    Plus, it's also confiming the integrity of the L202's set of inductive filters.

    Final test would be to test the D201 and D202 steering / isolation diodes.
    Do a swap probe leads in low ohms test on each one and if not being dead shorted, then do a like diode test mode in order to get / ascertain their forward voltage drop / loss in hundreds of millivolts.
    Do note that they are using 1N5822 Schottky diodes, in order to have a low voltage drop / loss since they are being used on both legs.
    Also they are 3A rated . . . a bit of overkill in this situation / application.
    Now . . . .waiting to see if you either find a wiring discontinuity path or a shorted diode(s) .

    Le TECHNICAL REFERENCING SCHEMATIQUE . . . . .
    [​IMG]



    1N5822 Diode Data Sheet
    http://pdf.datasheetcatalog.com/datasheet/fairchild/1N5822.pdf

    73's de Edd
     
    Last edited: Sep 16, 2017
  15. Jimkarl

    Jimkarl

    43
    2
    Aug 23, 2014
    I think the mystery is solved - they sent me the wrong power supply. The keyboard needs neg tip/positive ring as written on the back of the unit. The power supply is not marked but when measuring with negative on the tip and positive on the ring I get -12V instead of +12v. I have to order another.
     
  16. 73's de Edd

    73's de Edd

    2,726
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    Aug 21, 2015
    Sir jimkarl . . . . .
    That is exactly what the schematic is showing . . . central pin is NEGATIVE.

    . . . .
    OR . . . . if the 2 conductor wiring used between the wall wart and it's end conductor plug is not being all hidden within a round cabling.
    And happens to be utilizing a visible pair where you can see the two insulated and separate wires being placed side-by-side, with a very thin connective plastic web in the center between the two . Basically it's being just like we see on MUCH-MUCH larger, A. C. power Line cord .
    If you are so lucky, you come back 6 inches to a foot or so and run a Magic marker along one wires side about 6 inches . . . or a foot or even at the midway point and then cut the wire pair.
    Then you lay out the wires to be able to make a soldered and STAGGERED splice that will leave about an inch or so of separation such that touching of wires is not possible.
    Then you slip on two short lengths of heat shrink just a bit larger than the diameter of a single wire. Then two slightly larger than the combined wire pair go on, with one being slightly longer.
    Strip the 4 wire ends about 1/4 inch and solder tin.
    THEN do a polarity check against your previous black marker indexed wire to confirm making a polarity reversal, then butt solder and slide on the individual heat shrink collars on to insulate the individual spliced wires.
    Then the shorter larger diameter shrink gets centered over the splices and is shrunk down.Then the slightly longer heat shrink is centered on that to cover it.
    End result is being a small polarity reversing pod.
    No waiting for exchange or further trans shipping charges, along with achieving almost instant satisfaction.

    73's de Edd

    .
     
    Last edited: Sep 16, 2017
  17. Jimkarl

    Jimkarl

    43
    2
    Aug 23, 2014
    yes I could reverse the polarity of the plug but then I cannot return it and I need (want) a good power supply in resale condition. I'm not in any hurry, just frustrated that the ad was wrong and shouldn't have included this model. Wasted my time and everyone's here on the forum too. The latter is my fault because I should have checked/measured the polarity on that power supply before ever opening the case up. I just assumed it was sold for the correct purpose/model....
     
  18. ffets

    ffets

    3
    0
    Mar 6, 2018
    Hello Everybody,

    I read with attention this post because I have to repair a Casio wk-3200 which is the same as Casio wk-3700. Furthermore, I have the same problem as explained in the first post. I have no power up when I supply the piano with the official Casio AC adaptator. If I supply with batteries it's the same it does not work.

    Firstly, I desolder the connection between main board (SUB PCB reference M734-MA2M : the one which is supplied by battery) and the AC adaptator board (SUB PCB reference M734-MA3M : the one which is supplied by the AC adaptator). After that if I supply with batteries all is ok : the piano works.

    Secondly, I found the problem on the AC adaptator board (SUB PCB reference M734-MA3M) : L202 is in short circuit. If I desolder it and if I supply directly on footprints the board works. I measure ±3Ω between the pins 1-6 and 3-4 but also between 1-3 and 4-6 !

    My problem is that I don't find the component L202 which reference is "SFC99-01" according to the schematic. Can anyone help me to find a component which can replace this one ? Do you know an equivalent ?

    Thank you for your answer.

    ffets
     
    Last edited: Mar 6, 2018
  19. ffets

    ffets

    3
    0
    Mar 6, 2018
    Hello everybody,

    Hopefully, according to the schematic L202 (reference SFC99-01) is the same reference as L206 and L209.
    I think I will use either L206 or L209 for the L202 location and lost the function associated to either L206 or L209.

    I measure L209 with an RLCmeter and I found :
    pin 1-6 : 105µH, 0,21 ohms
    pin 3-4 : 105µH, 0,21 ohms

    Thank you.
     
  20. 73's de Edd

    73's de Edd

    2,726
    1,114
    Aug 21, 2015
    Sir ffets . . . . .

    That's the way to do it.
    Since that is being an EMI / RFI filter from the external power supply to the separate power supply divisions that are being made within the unit.
    The one supply of MAIN interest will be its dedicated switch mode power supply . . .IC201 and support parts . . which I included within my schematic referencing being supplied .
    Your filter sort of cleans up a possibility of your " switch mode generated crap waveshapes" from creeping out onto the AC line and being a "bad neighbor".

    Just using wire jumpers will suffice on the BATTERY supply which you are taking its chokes from.
    You now certainly don't have to worry about inter EMI / RFI when being battery powered.

    Be sure that you check that series diode D202 to see if it is shorted, before you power up the unit !
    WHY ?
    Considering that this unit is being an unknown to you . . . . . . and has not been under your nose since its day of acquisition. . . . .therefore you know its history
    Because . . . . . there are some Dumb Dora's and Casper Pee Klodds out there weeding thru thrift shops finds, who think that a Wall Wart is a Wall Wart is a Wall Wart.
    IF it will just plug into something.
    Should a fit have been made with an AC supply output it could pop the diode . . . . .perceive of the first electrolytic that it ties into, as being a short circuit , and heat up the choke coils . . . .where the windings heat up the interwinding insulation and let the enamelled wires short together or eventually one coil could open.

    73's de Edd
    .....
     
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