Pachinko Machine Sound Level Attenuator

Sound Level Attenuator picture #1
Sound Level Attenuator picture #2
Sound Level Attenuator picture #3

This circuit was designed for and tested on a Misuho Corp "Marine Battle" machine. It will likely work fine on similar machines. As with ANY MODIFICATION, be careful, and try at your OWN RISK!

The accompanying diagram shows the layout for a resistive network for reducing the sound level by attenuating the audio signal by 4x (12 dB) prior to the speaker. The network is designed to offer constant resistance of approximately 8 ohms to the amplifier, thereby keeping the amplifier operation as near to normal as if only the speaker were connected. The optional resistor shown on the diagram will increase the attenuation to 5x (14 dB).

Two-watt 5% metal oxide power resistors were used in this implementation. The network remains cool to the touch even when a "Big Chance" is hit (music is playing). One-watt resistors are a possibility, however, the price differential is only a few cents each.

The resistors were purchased from Mouser Electronics . They are XICON brand, Mouser part #282-16, $0.19 each. Shipping and Handling cost more than the 10 resistors purchased for the two networks. Similar resistors are available from numerous other sources.

The diagram shows the network soldered directly to the speaker terminals. As an option, quick disconnect female lugs could be used on the speaker end of the network to allow the network to be easily applied and removed from the speaker.

After installation, play the machine until a "Big Chance" or Bonus is hit. After letting the music play for several minutes, check the resistors to assure they are not hot.


Photos of the network attached to the speakers of Mizuho Corp. Marine Battle machine