MAIN CIRCUIT DESCRIPTIONS
Below are simple descriptions of each circuit block. Refer to circuit diagram for number.

1) Tape interface input circuit:
Consists of amplifier and comparator. When command is executed, data on this line is input to the CPU accumulator’s 7th bit.

2) CPU:
A CMOS 8-bit microprocessor IC24 (8OC85) featuring low power consumption. Virtually all POLY-800 functions are handled by this CPU.

3) Reset circuit:
IC40 (PST518) is a 3-pin IC used for reset. It generates an initial reset voltage of about 4.2V.

4) Sequencer tempo clock oscillator circuit
The tempo circuit includes, lC28 (TC4OH074) and l/2 of IC36 (which is l/2 of a TL072). \ . The tempo control is connected to CN2 pin 1 providing .10Hz+/-20% at the knob’s 0 position and lOOHz+/-20% at the 10 position for CPU interrupts. If this circuit fails, then there will be no sound from the sequencer section.

5) lnterrupt oscillator circuit:
This oscillator cycle is used for the EG, MG, LED displays, and S/H time division processing. Oscillator frequency is 24OOHz-360OHz. Interrupt order is by priority. If this circuit fails, EG operation and LED indication may become erratic.

6) -Address Decoder:
TTL circuit decodes addresses for RAM and other ICs.

7).ROM (8192words x 8bit PROM)

8) RAM (2048 words x t 8bit static RAM)

9) Address latch:
IC latches according to CPU ALE (Address Latch Enable) terminal output signal since CPU uses address LSB 8bits together with data bus 8bit input.

10) Peripheral I/O:
PA. PB, and PC ports are all used for output. The internal timer is used for the interface IC26 (63B50) reference clock. The CPU 3MHz clock frequency is divided by 6 to obtain 5OOkHz. RAM is used for the program working area.

11) LED display drive circuit:
IC30 (BA618) and IC31 (M54513) form a 6 x 8 matrix for time sharing indication by the panel’s 7-segment LED display.

12) 8-bit D/A converter:
Uses CMOS noninverting buffer IC32 (HD14050or”4050”), and 8R9 {RKM10L253F or “BR9”) a 10-pin (Rm25kohm) R-2R ladder resistor in D/A converter with output of 0V~4v.

13) Extamal DC power supply ripple filter:
Diode D2 is used to protect the circuit in case of reverse AC adapter polarity.

14) LED display power supply:
Circuit is designed so that LEDs become dim when battery voltage drops below rated level. (about 6V)

15) +5V power supply:
This circuit design is employed because it maintains normal operation up until just before the batteries drop below rated voltage of Volts (about 6V)

16) -5V power supply:
A type of C DC-DC Converter.

17) Bend depth circuit (KLM-599 PCB):
Because MIDI is used. R6 and R7 assure correct joystick center values.

18) AID converter comparator.

19) Master oscillator:
Varactor VC1 and coil KL-003 are used in the oscillator circuit. This generates a frequency of-about 2MHz at the tune knob’s center position. This is divided down (to about 1MHz) to supply the TG. (CL1, CL2) Bend and vibrato’ control voltages are D/A converted by IC35 (3404) and applied to the oscillator.

20) EG S/H circuit:
EG values calculated by the CPU are output by timc sharing and input to the TG. LED diodes for each voice are there to smooth the stepped transition.

21) Keyboard panel switch input circuit:
A 9 x 8 matrix is formed by DTC5, lC34 (TC40H138). and IC33 (TC40H240). This handles keyboard and panel switch outputs as well as output from the comparator in circuit diagram (18).

22).Detune circuit:
Lowers frequency by thinning out clock pulses

23) Tape interface output circuit.

24) CV circuit:
Performs time division output and s/h on CV for VCF and master oscillator.

25) 6-bit latch circuit:
A &bit control output circuit with 2 bits for detune. 2 bits for DC0 waveform switching, 1 bit for A/D converter, X-Y switching, and 1 bit for noise gate control.

25) 6bit latch circuit:
A 6bit control output circuit with 5 bits for S/H control and 1 bit for chorus on/off switching.

27) VCA + VCF circuit:
The ICI (NJM2069) has three internal VCAs and one internal 24dB/oct VCF (LPF:). SIG1 and SIG2 respectiveIy receive mixed DCOl and OC02 inputs from the TG;-LEVEL1 and LEVEL2 are Control input terminals.
The other VCA is for noise only. The 9pin (VCA LIN IN) is its control terminal. . .
M, EG INT and CUTOFF, KBD TRACK are controlled separately and input to VCF LOG.
See REFERENCE DATA for details.

28) Analog switch circuit:
Performs DC0 waveform switching and joystick AID convertor input switching.

29) Noise generator.

30) MIDI interfacecircuit:
This is a standard type MIDI interface circuit employing the MlD1 interface IC26 (ACIA63B50) and high processing speed photocouplor PC. 1. ( PC900)022 is used to prevent destruction of the photocoupler LED in case a reverse voltage is applied. Rll9 (220 ohm) and R 121 (220 ohm) resistors an? for prevention of damage in case of excessive current. The circuit is designed to provide a data transmission rate
of 31.25 k baud (+/-1%)

31) Waveform synthesis circuit:
Using the TC's various foot outputs (16’. 8’, 4’. and 2’), this produces 2-waveforms, one by addition on a 1=1=1=1 bask and the other using the ratio 1=1/2=1/4-l/8. 
The block resistor BR5 (RKC l/8 64 33K) is made up Of four 1/8W 33k resist&s (l=1=l=l). BR6 (RM00470) is 10K ohms using R. 2R, 4R, 8R (1=1/2=1/4=1/8).

32) TG (Tone Generator):
An IC having eight sets of dividers and VCAS. See REFERENCE DATA for details.


KLM-597,598 
KLM598 consists of the chorus circuit and headphone amp circuit The VCF output signal transits noise gate Fl (2SK381) and is input to compressor IC3 (NE570): then
IC4 (M5224P) detects the envelope.
The clock generator circuit which drivor tho 8BO IC makes IC7 (M5224P) generate a triangle wave which comparator IC8 (393) converts to a sawtooth wave with a change of pitch for a mom natural chorus effect.
F2 (2SK331B) at the output is an FET for chorus on/off switching.

KlM.597 ‘includes the panel section LED display and switch matrix circuitry.