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2. Sound source ROM

In the sound source ROM, 2 pieces of 1M bit mask ROM are used. The address bus and the data bus are connected to the gate array for sound source and performs chip-select of the address higher 2 bits (RA17 and RA18) of the gate array for sound source after decoding it by IC12 (HC139). This bus is also connected to IC card of KLM – 6029 and accesses the sound source data.

  

4. KLM-6028 (POWER SUPPLY SECTION)

The power source is converted as follows using

an AC adaptor of 9V:

a +5V

Converted to +5V by a three-terminal

regulator IC7 (78M05FA).

b

Converted to – 9V by a switching power

source circuit equipped with IC18

(IR3M03A; switch · regulator · controller).
 

3. Decoder

IC12 (HC139) decodes from the address RA17 and RA18 of the gate array for sound source and selects the sound source, chip of ROM, and IC card.

  

5. KLM-6029, 30, 31 (PANEL, VOLUME,

INST KEY SECTION)

1. LCD

1'he LCD module displays characters under the

control by CPU port A (PAO – 7) and PB5 – 7.
 

4. D/A

IC22 (MB4072P) multiplies and converts from digital to analog the source data sent from the sound source ROM or the ROM card and the envelope signals outputted from REF ports (REF2 – REF9) of the sound source gate array.

 

5. Multiplexer

IC25 (HC4051) divides signals which are converted by IC22 (MB4072P) to L and R positions according to the channel select signal from the gate array for sound source.

 

6. LPF

The sampling clock (25.0 kHz) of L and R signals which are divided by IC25 (HC4051) is eliminated by a LPF (fc = 12.0 kHz) consisting of a three-stage RC and IC29.

 

7. Noise reduction

IC21 (NJM072S) performs half-wave rectification to convert the signal into the DC voltage value and the pair transistior @19 (2SA 1239) outputs it in current.

IC28 (NJM13600) is controlled by the current outputted by $19. The cut-off frequency functions as LPF to open from the low area to the high area.

  

2. LED (RUN, REC, MODE and INST line

selection)

IC2 (HC574) latches the data of the CPU port A

and lights LED.

 

3. Key matrix

The key is scanned at the port A (PAO – 4, PA6) and CPU reads the data of the key being pushed through the port of gate array (MB64HB117).

 

4. Volume substrate (KLM – 6030)

Q~ The volume slider is used to control the output sound volume. (L, R/MONO, Phone)

Ob The data slider divides the current/voltage and input its value to the analog port AN1 of CPU.

 

5. Inst key substrate (KLM – 6031)

On this substrate, there are seven inst key switches and one inst line selection switch, which are respectively connected to the dynamics circuits of the main substrate (K LM – 6028).

  

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