●No sound is produced.
[Ensure that you are using new batteries.]
Be sure to always use new alkaline batteries to replace any that have run out of power. Please note that rechargeable NiCd batteries and non-rechargeable Oxyride and nickel-based batteries should not be used. The SX-150 has been designed for use with a 6-V power supply. Most rechargeable batteries produce a voltage of 1.2 V (or 4.8 V for a set of four); meanwhile, Oxyride batteries have a voltage of 1.7 V (or 6.8 V for a set of four). In both cases, therefore, the synthesizer may not operate as designed. Also, any accidental short-circuiting of such batteries can lead to dangerous situations such as the melting of components and the outbreak of fire.
[Check all connections.]
Ensure that the battery-box connectors are fully engaged with the corresponding circuit-board connectors. Securely reconnect any loose connectors.
[Check the speaker cords.]
If a cord has become detached from the speaker, solder it correctly back into place.
[Check the connections of the slider-panel cords and electrode.]
The two sides of the slider panel should be secured in place using screws with contact rings sandwiched between them. The contact rings should be as flat as possible against the surface of the slider panel. If sound is produced when touching the electrode to the screw heads but not when contact is made with the slider panel, it is likely that poor contact at these contact rings is the cause. In such a case, remove the screws, straighten the contact rings, and then replace the screws. Similarly, the electrode’s contact ring should be assembled as flat as possible against the solder part of the circuit board.
●Pitch increases towards the left of the slider panel and decreases towards the right.
[Check the colors of the cords connected to the slider panel.]
If the blue and while cords are connected in reverse, the relationship between pitch and position on the slider panel will be inverted.
●Pitch does not change when the electrode is moved along the slider panel.
[Check the screws at each side of the slider panel.]
It is likely that the slider panel is not correctly assembled. If the pitch remains constantly high, check the screw on the left-hand side. In addition, poor contact between the slider panel and its contact rings can also prevent sound from being produced correctly, even if the screws are tight. Ensure that the contact rings are as flat as possible against the surface of the slider panel. If any of the black rubber part gets caught between the contact rings and the slider panel, the electrode may not produce any sound when touched against the panel. If such a case, remove the screws, straighten the contact rings, and then replace the screws.
●Sound is produced even when the electrode is not touched against the slider panel.
[Check the dial settings.]
In certain cases, sound is produced when the LFO RATE dial is set fully clockwise and the CUTOFF dial is set to the 12 o’clock position or thereabouts. It is caused by the LFO frequency entering the audible range and sound is emitted through a filter. This is not a design flaw.
●A capacitor on the circuit board is bent over.
[This is not actually a problem.]
The C15 capacitor located on the circuit board at the side of the battery connector may be bent over. This is done intentionally to ensure that the board fits into the case, and it does not lead to any operational problems.
●Nothing can be heard when audio is input via the EXT.SOURCE jack.
[Check the volume and pitch.]
The EXT.SOURCE jack is used to control the synthesizer using electrical audio signals input from an external source. It is not used to directly process audio signals; rather, this connection is designed to allow the pitch (oscillating frequency) of the synthesizer’s voltage controlled oscillator (VCO) to be modified by the amplitude and frequency of the input signal. Accordingly, it cannot be used to apply effects to external audio. The design of this control circuit assumes that a Gakken Theremin mini will be used as the source of external audio. Therefore, because the signal is taken from Theremin mini's speaker, the input signal must be relatively loud and high pitched. The volume in particular must be high enough to drive the speaker, and if necessary, therefore, it should be boosted using an amplifier before being input.
●Sound can only be heard on one side of headphones connected to the OUTPUT jack.
[The OUTPUT jack is for mono sound.]
As the SX-150 is a monaural instrument, sound will only be heard on one channel if stereo headphones, earphones, or amplified speakers are connected to the OUTPUT jack. Normally, sound is output on the left channel in such a case.