Teisco SX-400 (1980-82)

The SX 400 was made under the name Teisco from the year 1980 to1982.
It is a four voice programmabel (8 Preset and 8 Userprogamms) polysynth with CV and Gate.
The oscillators have sine ,saw and rectangle (PW and PWM) waveforms and a suboscillator.
They are switchabel as a dualvoice, a fourvoice or a monovoice.
In monomode you can give each of the four oscillators a diffrent range and finetuning (16´ 8´ 4´ 2´).
The filter has 24 dB and resonance with selfoscillation. Modulation is possible by LFO 1 or 2 and
+ and - ADSR. Behind the VCA is still a HPF and a ensemble. The ADSR can trigger  by LFO 2.
The keyboard is pressure sensitive with diffrent routings, portamento and glissando is also available.

Picture gallery

Press pictures for close-ups




Inside                              Keyboard                    CPU board                  PSU board

VCO board                 Mod board

Battery Mod

Please check the condition of the backup battery.
The SX-400 is vulnerable to leakage from the NiCad memory backup battery located on the CPU board.

On  trhe below[picture, the standard NiCad battery has been replaced with a non-rechargeable
Lithium battery fitted in a holder.

When you decide to do this, you MUST remove the diode that allows charging. (clearly marked in picture)

Press picture for close-ups


Here's a binary dump of the EPROM contents.
It's proberly labeled "1P002".



A full color copy of the complete manual in one pdf file. 28 pages, 5,09MB. User Manual

Service Manual

Synthdoctor has made the complete service manual available. If your synth needs a repair, contact him.
He is specialized in repairing old/new synths, etc.http://www.synthdoctor.nl

Download the service manual here.
And here's only the CPU board section of the servicemanual. 3 pages. 3,1MB. CPU board


Huge article/review of the SX400 and other Teisco synths

Big thanks to Stephen Lenham, Ingo Rippstein and Martijn aka Synthusiast.

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