Sorry for the delay in updating this, but it really has been extraordinarily busy over the last several months.
This is an interesting machine, and we have had two of them over the last few months, both of them purchased by the same person and both needing different kinds of work to make them perfect. Unlike the badly designed CPU systems of the SX400, the 210 has a delightfully simple and logical approach to fulfilling it’s task.
This synth has a lot of things in it’s favour, 8 Voices each with SSM2044 filters, a 3 phase chorus unit (both like a Korg Polysix) and 32 presets just like the Polysix. Each parameter has a button and the variable ones are instantly adjustable using the rotary encoder. The Black switch tops are for on/off functions and the Grey ones are for variable parameters. Before the days of LCD displays, this synth has six digits of 14 segment starburst LED display which allows you to name presets with real names, programmed using the keyboard to select the letters and/or numbers that you want.
But there is one small fly in the SX210’s ointment, and while it may seem trivial, it makes using the synth very difficult if the LED’s above each switch don’t work. The LED’s above the switches protrude above the buttons by a couple of millimeters, and this is enough to make them vulnerable to damage from either transit damage or from overly energetic button pressing. Like most synths of the era and even to this day, LED’s are driven in a grid by high speed interfaces from the main CPU, so losing one LED due to a pcb track break could stop 4 or 5 others from functioning, and the way that the SX210 is designed is to balance the current through the LED’s of the whole panel to avoid too much flicker and variations of brightness.
The PCB tracks on the front panel devoted to the button LED’s are very small and thin and easily breakable and this seems to be an Achilles heel of this synth, both SX210’s that came through here had problems with the LED’s and in both cases broken (and practically invisibly so) tracks were the reason.
One other big issue is the NiCad battery that the synth was originally fitted with, it can go bad and leak like in so many other synths of the time. Most of the remaining 210’s out there had this sorted out years ago, but this picture is of one that wasn’t.
Everything in that area had to be cut out and replaced and in the final analysis, three pcb tracks had been eaten away and as this section drives the gates for the envelopes of the voices, dead voices were the result.
This is a great synth when sorted out and it’s only real Achilles heel is the lack of a MIDI interface for it, which is slightly ironic as it’s cassette interface in and out are run from the serial interface of the 8031 CPU chip which is certainly capable of handling MIDI. Someone out there, just write some new firmware to handle MIDI using the CPU’s internal abilities and we can sort out the hardware end. An SX210 with a good MIDI interface could be the next big thing in the synth world.