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Hello,<br>
<br>
I built a replacement for the SSK board in a Yamaha CS15,
essentially using Old Crow's approach. My schematic is here:<br>
<a class="moz-txt-link-freetext" href="https://florian-anwander.de/yamaha_cs15/CS15_SSK_FA__Nano_2_sch.png">https://florian-anwander.de/yamaha_cs15/CS15_SSK_FA__Nano_2_sch.png</a><br>
The original schematic is here:<br>
<a class="moz-txt-link-freetext" href="https://florian-anwander.de/yamaha_cs15/Yamaha_CS-15_Servicemanual.pdf">https://florian-anwander.de/yamaha_cs15/Yamaha_CS-15_Servicemanual.pdf</a><br>
<br>
Everything works perfectly. Only after switching on, VCO2 plays in
an extremely wide range, while VCO1 only plays over one octave
across the entire keyboard. I can "cure" this by briefly
interrupting the CV connection to VCO1.<br>
<br>
The difference between the two VCOs is that the TA7505M OpAmp, which
provides the buffering for the portamento circuit, is connected
directly to the IG00153 of VCO1; while for VCO2 there is an
additional OpAmp stage before the IG00153 that provides the detune
voltage. In my circuit I use a TL072 instead of the Toshiba TA7505M.<br>
<br>
Now I am looking for the datasheet of the TA7505M to find out what
could cause the problem. There doesn't seem to be the datasheet on
the web.<br>
<br>
Do any of you have a Toshiba Databook from the late 70s? Or does
anyone have an idea how I could solve the problem in a simple way
without having to make a new board (it is clear that I could also
put a buffer in front of the IG00153).<br>
<br>
<br>
Best regards<br>
Florian<br>
<pre class="moz-signature" cols="72">--
<a class="moz-txt-link-freetext" href="http://www.florian-anwander.de/">http://www.florian-anwander.de/</a></pre>
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