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Roland FP2 electric piano

Discussion in 'Electronic Repair' started by N_Cook, Jan 30, 2013.

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  1. N_Cook

    N_Cook Guest

    No R speaker nor R line out, L &R phones out seem ok, as does the speakers
    on/off sw. Amp hiss from the R speaker only, L is fine.
    I got inside this 7 octave thing without breaking any foil ribbons. The
    phones input socket switches seem ok, so does the line out sockets. But the
    Line-In Left/ Mono input has a bad bypass switch. Although it is in a
    position that would suggest a Ring contact it seems to be a tip contact
    switch, difficult to trace the local traces as vias etc.
    Anyone know if the problem there would cause the loss of one channel. As
    difficult to "bench test" this sort of item, any other areas to look at
    before some sort of reassembly?
     
  2. N_Cook

    N_Cook Guest

    I've only run it so far without the keyboard half connected, next time I
    come across one I will try external input feeds L & R before dismantling.
    These line in/outs seem to be simple mono so. with tip sw, no ring contacts
    for sensing of R-S connection of a mono jack.
    The "switching" logic seems to be if In-L/Mono tip is no longer grounded
    then feed that signal to both L & R amps ; if you feed a signal in the R as
    well and so its tip also is no longer grounded then defeat the signal from
    L-in going to the R ch , and allow the R signal to R amp. Or something like
    that, I still don't see why failed tip sw and no signal in there, would
    defeat the keyboard output to the R amp.
    The phones outputs were only operating as 2 mono outputs, now 2 stereo
    outputs from L&R ext inputs . Hopefully that tip sw failure was the cause .
    I suppose regular repairers of Roland and Yamaha pianos etc have long frames
    that can hold, open, both halves safely while powered up , plus ribbon
    extenders.
     
  3. N_Cook

    N_Cook Guest

    No change, same loss of one speaker. I'll have to look out for some sort of
    basic midi keyboard for the next time, not one of my current bits of test
    kit.
    No convenient overlay marking of L-out/R-out on the main processor board or
    on the PA board. I don't suppose that info of which header/pins those
    signals should be on, is out there somewhere. I've found some long P-K bolts
    and with spacers should be able to fix the 2 body halves adjascent and 180
    degrees apart , and work on powered up , to at least find where those audio
    signals lay. This keyboard has been dropped it would seem , stoving in part
    of the base chipboard , up against where the ribbons connect to the keyboard
    but as the keyboard works as such, then that local area was unaffected , I'm
    assuming.
    Then hopefully couple some test signals in there without the keyboard
    connected
     
  4. N_Cook

    N_Cook Guest

    I decided that lash-up too whisky. The digital seems quite well separated
    from the analogue on the PA board and 2 lines seem to come from off board to
    p2 and p6 of an M5218 dual op-amp SIP via electros from CN1 p6 and p8.
    Injecting 0.1V in those points carried through to both the speakers. That
    CN1 header traces back to the display board with vol and balance pots on it
    so a job for tomorrow
     
  5. N_Cook

    N_Cook Guest

    I'll know for next time.
    Low profile 7 pin ALPS 103B 502C pot, I could get tending to 0 fully CW and
    CCW pins 2,4,6 but not another triplet of pins. I did not realise these were
    bass compensation? centre tapped dual 10K pot tracks
    p2,4,6 one pot with 5K mid tap p1
    p2,3,5 mid tap p7
    and p2 common to both tracks
    presuambly compacted grease lifting the flimsy wiper, from getting inside.
    Hopefully that was the problem rather than me not realising these were non
    standard pots.
    Will try tracing the p6/p5 upstream signal side back to the main processor
    board or wherever for non-kbd testing purposes
     
  6. N_Cook

    N_Cook Guest

    Back working again. Pin 6 and 7 of the vol pot is a good test point. They
    trace back via electros to p1&3 of CN1 jumpered via 0ohm Rs to CN4 p10&12 of
    the large ribbon and back to CN13 of the main processor board .
    Now to find something to cover over the hole in the chipboard and replace
    all the screws etc
     
  7. N_Cook

    N_Cook Guest

    Should read pot Pin 5 and 6 for test points

    At least Roland FP. are not as heavy and awkward to handle as Yamaha P..
     
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