Yamaha amplifier case study-Potentiometer Damping Grease

Yamaha DSP series amplifiers can be purchased second hand online at low cost. Older models have a common problem with the volume control because the volume control knob movement often does not correlate correctly with the dB level readout on the VFD screen reading.

The fault is due to the fact that the original potentiometer damping grease used by Yamaha has dried up over time.

The potentiometer can be refurbished and the dB level readout issue corrected with some effort and an application of a synthetic damping grease.

The only way of accessing the potentiometer is to disassemble the amplifier. As always when working on electrical equipment, make sure the unit is unplugged/disconnected from any power source before starting work.

Challenges

Unlike the original lubricant, the new damping grease should last the functional life of the amplifier, be able to perform at the elevated temperatures required by the amplifier and be compatible with the plastics used for the components. A higher viscosity (thicker) damping grease is needed to improve the tactile feel of the potentiometer.

Solution

  • A synthetic damping  grease of a high viscosity to give a ‘velvet feel’ to the component when rotated.
  • A Polyalphaolefin (PAO) based grease should be compatible with any plastics involved.
  • The damping grease must not dry out, be very durable and last the functional life of the device.

Product Selection

Nyogel 774VH (Very Heavy)

Applying The Grease

The potentiometer needs to be disassembled first and any old remaining grease wiped away. We also recommend that the rotary encoder surface (circular metallic part at the base of the shaft) is wiped/cleaned as debris/dust could have also built up over time on the encoder. Grease is not applied to the encoder.

The Nyogel 774VH should be applied where the black plastic shaft meets the metal case that shields the encoder.

It should be noted that the Nyogel 774 range is available in 5 levels of viscosity, from the Nyogel 774VL (Very Light), through to the Nyogel 774VH (Very Heavy). Damping is a subjective matter, most of our customers prefer the tactile feel provided by Nyogel 774VH or the slightly less viscous Nyogel 774H (Heavy) as a volume control grease.

Results

The Nyogel 774VH greatly improved the tactile feel of the volume control knob, giving the potentiometer rotational movement a velvet, quality feel.

The problem with the inaccurate volume readings on the VFD display was also corrected by returning the volume control operation to a factory fresh level of performance.

THE APPLICATION OF NYOGEL 774VH returned the volume control operation to a factory fresh level of performance.

Please note that we also offer specialist lubricants to prevent electrical contact wear in sliding position sensors and potentiometers. Lubricants used on these delicate mechanisms must be strong enough to prevent contact wear but thin enough throughout the operation temperature range to prevent contact hydroplaning and the resulting intermittencies.

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