[sdiy] strange symptoms

[elmacaco]

What a neat trick!!!

I love this list!

Ed
  ----- Original Message ----- 
  From: Michael Boracci 
  To: gilwein at walla.co.il ; synth-diy at dropmix.xs4all.nl 
  Sent: Tuesday, October 14, 2003 9:49 PM
  Subject: RE: [sdiy] strange symptoms


  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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