[sdiy] Datasheet Toshiba TA7505M / modern replacement

[houshu at muj.biglobe.ne.jp]

Hi Florian and list,
Japanese datasheet with internal circuit is here:
  https://wakamatsu.co.jp/biz/products/detail.php?product_id=13140412

Its internal circuit is basically like 741, but input npn pair is 
replaced by N-channel JFETs.If slow response is essential, LF13741 is a 
candidate.


Best,
Sam HOSHUYAMA
Kawasaki, JAPAN

------ Original Message ------
差出人: "Florian Anwander" <fanwander at mnet-online.de>
To: "*SYNTH DIY" <synth-diy at synth-diy.org>
送信済み: 日曜日, 2025/1/5  00:27
件名: [sdiy] Datasheet Toshiba TA7505M / modern replacement
      Hello,

      I built a replacement for the SSK board in a Yamaha CS15, 
essentially using Old Crow's approach. My schematic is here:
 
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>
      The original schematic is here:
  https://florian-anwander.de/yamaha_cs15/Yamaha_CS-15_Servicemanual.pdf 
<https://florian-anwander.de/yamaha_cs15/Yamaha_CS-15_Servicemanual.pdf>

      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.

      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.

      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.

      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).


      Best regards
      Florian
      -- http://www.florian-anwander.de/ 
<http://www.florian-anwander.de/> 
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