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<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=309243505-19032004>My 4D
and 4E both worked right off the bench at +/- 15V. The 4D had some rework
on the PCB I don't remember the 4E having any.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=309243505-19032004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=309243505-19032004>Do a
good visual inspection and make sure all the solder joints look
good.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=309243505-19032004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=309243505-19032004>Might
check the cap to see if it's the right value. The difference between a 103 and
104 value cap is pretty substantial.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=309243505-19032004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=309243505-19032004>Also
look to what voltages the saw works at. If I remember right it should be about
0V to 1/2 +V.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=309243505-19032004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=309243505-19032004>Then
it could be bad parts.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=309243505-19032004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN class=309243505-19032004>It
would help a lot to if you had an oscilloscope to see what is going
on.</SPAN></FONT></DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=309243505-19032004></SPAN></FONT> </DIV>
<DIV><FONT face=Arial color=#0000ff size=2><SPAN
class=309243505-19032004>Jay</SPAN></FONT></DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #0000ff 2px solid; MARGIN-RIGHT: 0px">
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Tahoma
size=2>-----Original Message-----<BR><B>From:</B>
owner-synth-diy@dropmix.xs4all.nl
[mailto:owner-synth-diy@dropmix.xs4all.nl]<B>On Behalf Of
</B>Peng<BR><B>Sent:</B> Thursday, March 18, 2004 10:33 AM<BR><B>To:</B>
synth-diy@dropmix.xs4all.nl<BR><B>Subject:</B> [sdiy] VCO oscillation
problem<BR><BR></FONT></DIV>
<DIV>
<DIV>I'm having a problem with my VCO 4E from EFM. Assembled and looks nice
but the wave outputs all produce the same high-pitched screalling. It responds
to keytracking and LFOs as cv mod. Tried the trimmers: couldn't bring the
pitch down enough. Quadruple checked pcb, wiring, solder joints, etc. Started
poking my finger around the board ( as a beginner this is my scientic
troublshooting method ) , Got to the op amp that sums the cv inputs and
touched the capacitor in its feedback loop and the pitch changed slightly.
Tried attaching a bigger cap but this had only a very small effect. My best
guess is a problem with the feedback loop. Any pointers, suggestions, or links
would be of great help.</DIV>
<DIV> </DIV>
<DIV>Thanks,</DIV>
<DIV>Peng</DIV></DIV>
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