Octave Cat Restoration

Octave Cat Restored, just needs knobs and switch caps

Octave Cat Restored

I have done various Octave Cat’s and Kittens, from the original version, through SRM II. What they have in common is that they are tough to get going, and sorting out the keyboard contacts is always a major pain. This one though was the worst of the worst. It had been stored in a bad environment for many years, giving it corrosion and a bad case of filth. Worst of all though was that the bottom was missing, and the buss-bars/keyboard contacts were mangled, along with broken resistor packs. It was missing 5 of the j-wire activators, and all of the knobs and slider caps.

It was stripped, cleaned, and gradually rebuilt. I managed to straighten out the buss-barsDirty Octave Cat and contacts, re-bush it, and hand-clean the keys. Everything was cleaned, and the sliders/pots/switches treated with switch-cleaner. Some of the switches had to be opened and Octave Cat Mangled key contactsdeep cleaned in order to get them working. Electronically, some CMOS chips had failed and were replaced. VCO1 would not run at its lowest frequency, and I could see that a previous repair attempt had changed all of the suspect chips, plus there were a lot of component changes/ additions. I was fortunate in that another one came in, so I could compare and put it back to standard, and fix the original issue!

Life was then repeatedly cleaning and adjusting keyboard contacts, and fine setting it up until it worked reliably, phew! We purchased some knobs from Frys, and found that Sam at Syntaur has the slider caps. Doug at Synthparts thankfully had some of the j-wire acticators

18 thoughts on “Octave Cat Restoration

  1. Hi Chris,
    I’m in the middle of trying to restore an Octave Cat SRM II that sounds like it was in almost the same condition as the one you described. Do you have any advice on where to find the service manual/schematics for the later SRM II model? Any advice would be greatly appreciate. Thanks!

    • Hi Brian,

      I searched long and hard, and came to the conclusion that it does not exist on-line. I also tried other folks that work on the Cat and they will not take the SRM II in because of a lack of schematic. My solution was to trace the signal through on the keyboard interface circuit board, pin by pin, and look for where the signal went bad (this was not a recreation of the schematic, and not kept). Your most likely culprit, as was the case for me, is a bad CMOS chip, and for a couple of bucks you could just change them all as they are socketed.

      Good luck with your repair!


  2. Chris, thanks for the reply and info. I’ve got the feeling that
    you’re right and that those documents don’t exist online.
    Thanks for taking the time to help. I’ll try what you suggested
    and see where that leads. Do you know of anyone who does
    work on the SRM II ? I can certainly understand why they wouldn’t
    but I just thought maybe someone out there might know that
    synth. Again, a million thanks.

  3. I have schematics of Cat Octave SRM, and I think a tune-up guide. My Cat is working fine except for one oscillator is out I believe. Let me know if you need me to send any thing. I need caps on two of my sliders, and will check with Doug at Synthparts.

  4. Hello,

    This is a great entry, very informative!! I recently got a Octave Kitten that works but needs a major clean up/overhaul. One of the keys is broken in half and two switches have broken off.

    By any chance to do were to buy replacement switches and keys for the octave kitten? Also the white rubber siding on the wooden sides is missing and would like to replace with some sort of finish.

    Any tips for parts and schematics would really be appreciated!!!


    • Hi Ryan,

      Glad you liked the blog!

      Musicparts has a poor quality Kitten schematic for purchase. I have not found another copy anywhere for free download. Sam at Syntaur has CAT slider caps, you could ping him to see if he has any Kitten stuff (doubt it). For switches I tend to rebuild them if I can, scavenging around parts stores/Ebay for similar ones from the same manufacturer if it is physically broken. I do not have a Kitten here at present to see what keys it has in it, but you should be able to find a match (try sound doctorin as he has a key cross reference).

      Sorry this is a bit vague; welcome to my world of scavenging parts to fix 30 year old synths!


  5. Which of the reed switch bars is connected to red and which is connected to black? I’ve inherited a CAT that was taken apart and reassembled incorrectly…trying to sort it out. Thanks!

  6. Hello !

    I am contacting you from France. I am the owner of a CAT (with accordion keys…)

    But 2 switchs are broken ( a 2 ways and a 3 ways). I am a poor electronician… I found someone who could change them… but I have first to find the new switchs….
    Do you have any idea where I can found on the web thoses switchs?

    Thanks in advance for your king assistance.

    Kind regards


    • Alex,

      I have not found the original switch type online. I scour the surplus electronics stores for something similar, then typically have to construct a mounting for it on the circuit board.


  7. I have an Octave Kitten. It has the same bus bar keyboard as the Cat, I think? It would not make any sound when I got it. It seemed that the bus bars were just filthy and oxidized. I cleaned them as well as I could with denatured alcohol over and over. I tweaked the positioning of the keys and checked and rechecked that they would trigger. At first they were triggering, but all playing the same note. They seemed to respond to all envelopes, filters, volume, and all other controls. After more intense cleaning they are playing pitch up and down in steps, but the entire keyboard only covers the pitch range of about an octave. Like each key only goes up a small step. Do you think its still just a matter of more cleaning, resetting the keys, or could something else be wrong too? Any opinion or help is appreciated. Thanks a lot! -Max

    • The Kitten scales 1v/octave. You need to get a meter on the CV buss-bar to ground and see if it scales correctly, then debug from there.

    • The Cat SRM schematic is commonly available, it is the SRM II that isnt.

      THe only place I have found the Kitten schematic is http://www.musicparts.com:
      Octave-Plateau Kitten Synthesizer Schematic
      Contents: Schematics, Product Picture / Illustration, Introduction / Features, Specifications, Calibration / Alignment Instructions, Front / Rear Panel Illustrations, PC Board Layout, Semiconductor Generic Reference Numbers.
      Note: Original blueprint schematics dated 1977 from yellowed and faded blueprint paper, however we have been able to resurrect a decent usable image off of them. However please note that this is not perfect and some values are hard to read. (Dated 1977) (19pages/$35)

  8. Would you have any idea where to find replacement keys for a Cat? Would the keys from an Odyssey fit it?

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