[sdiy] strange symptoms

[Michael Boracci]

Have you looked for cold ( cracked ) solder joints? They can be very hard to
find, however now that the board is clean it will be easier. Breathe on the
board closely to create a fog on the solder joints. Hairline cracks will
show up as a thin ring around the pin which is protruding through the board.
You might be surprised to find many of these which is a common failure on
most wave soldered boards.

Thermal flexing over time can open these cracks and make problems occur
years after the board was made.




  -----Original Message-----
  From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of gilwein at walla.co.il
  Sent: Tuesday, October 14, 2003 9:01 PM
  To: synth-diy at dropmix.xs4all.nl
  Subject: [sdiy] strange symptoms



        Hi.

        I have that problematic Kawai SX210 which had it's battery leaking,
        probably causing it to behave strangely like playing notes
automatically
        and playing a few notes when you hit only one key.

        I clean all the defective are and replaced a few parts,
        replaced the battery and resoldered a few wires.
        also cleaned up the whole pcb.

        Than it actually stopped playing automatically,
        and a few notes when you hit one key,
        BUT, now it misses some notes sometimes,
        and sometimes when you hit a chord
        the sound comes out in pulses. Also it will play some notes
        with a slightly different sound than the preset used.


        I replaced a few capacitors and just when starting it up
        the dial wheel has stopped to respond and I now cannot edit
        any of the parameters !!!

        I noticed that there's a short between two transistor legs
        that comes on and off  (the transistor is not leaking and is OK).

        I mean sometimes the short is there but sometimes it is not .....

        how can this be caused and is this normal ?

        I also noticed that the EPROM chip and another (very) large
        chip made by Intel, are getting warm after a few minutes of
operation (but not too warm...)
        is that normal ?

        moreover, is there any chance that the EPROM programming
        has gone defected ?

        Thanks,

        I really want it to get fixed !


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