AX-M140 Music Bank

Hitachi AX-M140 music bank is a very useful part of the component system because it has a built-in PATA hard disk drive, and there is a socket at the front for a USB memory stick. This unit also has a serial cable connection at the back so one can connect it to a computer PC for transferring MP3 files.

Looking at the circuit, we see there is a bridge rectifier, and the centre two pins receive AC voltage from the control cable. The toroidal transformer in the amplifier unit of course generates this voltage. Just for fun, I fed it 12 V AC from a bench power supply and applied 3.3 V DC to the standby pin 22 in the control cable socket. I simply used another bench power supply for the control voltage, and heard the hard disk drive spinning up. Removal of this voltage makes the hard disk drive spin-down.

Interestingly Analogue ground, Left, and, Right are through pins 35, 36, and 37 respectively. Pin 26 is MP3 ON/OFF for controlling the device. I installed a USB memory stick with an mp3 file and pressed Play, and noticed the light on the USB stick flickering as if it was being accessed. I did not connect the audio signals to check; however, this is something I shall explore fully if the system controller IC is unobtainable.

Looking at the front buttons of all of these component units, we see that each has ts own dedicated set of controls, which leads me to think that they have a chance of operating individually with some modifications. If each of the units in the component system can operate individually, with their own dedicated power supply and RCA sockets for audio output, then that would go a long way to bringing this hi-fi working again. However, the biggest modification would have to be in the amplifier unit, which would require the removal of encoders and installation of potentiometers. The whole of the front panel would have to go, and a preamplifier circuit fitted to provide the bass and tone. The amplifier would need a selector switch for selecting the audio input signal.

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