This RS-09 died in a basement flood and has rusty bubbles all over its panel. It has a helpful piece of masking tape labeling the notes on the keyboard with their note names. We were tasked with fixing it basically for as little money as possible, but the only thing we could have done but didn’t do was make it look nicer.
The top octave synthesizer for this one was dead and I had to get a cloned replacement from Flatkeys. The replacement for this is the one called MK50240-RETRO on the Flatkeys site.
Repair Tips: The most important discovery of this repair was that the 4013 flip-flop that operates the “Octave Down” feature on this REALLY has to be a very old 4013. The RS-09 will NOT let you put in a new one or even a Harris one from the early 90s or try to evoke the behavior of an older chip by increasing pin capacitance externally. We confirmed this in a “controlled experiment” with two RS-09s (one of each of the two versions) and a bunch of different 4013s. This is something I keep a document to keep track of– CMOS ICs in specific synths that have to be NOS– and there aren’t a lot of entries in it. I should clarify that plenty of other synths from the same time period can use both new and old 4013s and I still don’t know what the deal is with this one.
Work done: Replaced top octave synthesizer with Flatkeys clone, replaced power supply capacitors, cleaned pots and switches, repaired flip-flop circuit between master clock oscillator and TOS.