Audio hiss fix

Issue

The MD785 exhibits a noticeable audio hiss on both the internal speaker and, even more so, on the external speaker output.
This is caused by the audio amplifier operating at a fixed gain, with only the input level being volume-controlled.
In addition, the menu and alert beeps are excessively loud, as the radio is designed primarily for vehicle installations rather than desktop use.

To significantly reduce the hiss on the internal speaker and to bring the beep level to a more comfortable volume, a 22-ohm resistor can be added in series with the positive lead of the internal speaker.

Fix

• Disconnect the power cable from the radio
• Disconnect the microphone
• Remove the three screws on the underside of the front panel
• Carefully remove the front display, taking care not to damage the ribbon cable
• Locate the speaker connector
• Desolder the positive (red) speaker wire
• Solder a 22-ohm resistor to the positive terminal of the speaker
• Solder the speaker wire to the other end of the resistor
• Reassemble the radio

If a 22-ohm resistor is not available, a trim potentiometer may be used instead to fine-tune the attenuation.

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