Otari MX-5050
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III/2III/4III/8BQ-II

BQ-II manual, Section 10 · Site-authored simulation

Simulating the AMP control board

The BQ-II's AMP control P.C.B. (PB45E0A, Otari drawing 3-6649) carries the record command logic, the two 555 clocks, the 1 kHz and 10 kHz test oscillators, the EQ select buffer and the power-on mute. This site redrew the sheet in KiCad 10 at Otari's positions and ran it in ngspice: five scenarios and 226 checks, each against an expected value or range, most worked out from the parts on the drawing and the rest logic levels, datasheet typicals and sanity bounds. This is a simulation of Otari's drawing, not of a physical board.

The redrawn sheet (SVG) · PDF · KiCad project (zip) · the scan in Section 10. Exported with KiCad 10.0.4.

Bench

What the simulation adds around the board, where the drawing stops:

  • The sheet's bench: +15 V, -15 V and +5 V (P5V) supplies; AF-B17 and AF-B18 grounded off-board; EXT OSC IN (AF-A5) at 0 V; EQ select (AF-B11) at +15 V, the Control PCB's low-speed state.
  • Switches to ground (MECHA REC COMM, CH1-CH4 REC, TEST OSC 1 kHz / 10 kHz, EXT OSC, LINE) are 0 V sources; an open switch leaves the pin to its pull-up.
  • REC LEDs (AF-A14 .. A18): a generic red LED from MUTE A (P.O.M.A) to each pin, in scenarios 2 and 4. The Mother PCB (3-6287) feeds the front panel's REC LED from P.O.M.A (AM3); the LED is off this drawing.
  • EXT OSC input: 1 V peak at 400 Hz, in scenario 3.
  • Power in scenario 5: the three supplies switch on as a step at 0 s (uic: every capacitor starts empty) and fall together, linearly, to 0 V over 50 ms from 4.0 s (assumed; the real supplies' decay is not on this drawing).
  • MUTE A loaded by 1 kohm and MUTE B by 10 kohm to ground, in scenario 5 (assumed; the channel cards' mute inputs are not modelled).

1. DC operating point, idle

CheckSimulatedExpectedBasis
+15 V supply current34.26 mA30 to 40 mA2 x RC555 (10 mA typ), 2 x NJM4559 (3.5 mA typ), the mute drivers
-15 V supply current9.747 mA8.755 to 10.7 mA2 x NJM4559 and R528
+5 V supply current8.657 mA7 to 11 mAR609, R610 into Q604 and Q605's base
GND B17 return21.15 mA18 to 24 mAboth RC555s return through AF-B17
IC401 control voltage10 V9.95 to 10.05 V2/3 of VCC
Q401 off: collector current≈ 0 µA0 to 1 µA
Q402 off: collector current≈ 0 µA0 to 1 µA
Q403 off: collector current≈ 0 µA0 to 1 µA
Q404 off: collector current≈ 0 µA0 to 1 µA
Q405 off: collector current≈ 0 µA0 to 1 µA
Q602 off: collector current≈ 0 µA0 to 1 µA
Q501 on, oscillator held off: base current305.1 µA274.6 to 335.6 µA+15 V through R501
Q502 on, oscillator held off: base current305.1 µA274.6 to 335.6 µA+15 V through R509
Q503 (EXT OSC gate) off: drain current0.015 nA0 to 1 nA
Q504 (LINE) off: base current≈ 0 µA0 to 1 µA
Q601 on: base current22 µA18.7 to 25.3 µA(5 V - VBE) through R602 + R601
Q604 on: collector current12.37 mA5 to 20 mADarlington with Q603
Q605 on (MUTE A at +5 V): base current1.777 mA1 to 3 mA
Q606 off (MUTE B released): collector current≈ 0 µA0 to 1 µA
Q607 on: collector current1.438 mA1.296 to 1.584 mAinto D602 and R611
C603 (mute timer) charged2.512 V2.3 to 2.7 VR604 / (R606 + R607) divider less Q603's base
EQ OUT at low speed12.27 V12.15 to 12.39 VR531 / R528 divider
AF pins, idle
AF pinnetidle (V)
AF-A1.2MUTE_A4.994
AF-A10CH3_REC0.000
AF-A11CH2_REC0.000
AF-A12CH1_REC0.000
AF-A13SRCLK9.678
AF-A14LED40.000
AF-A15LED30.000
AF-A16LED20.000
AF-A17LED10.000
AF-A18LED50.000
AF-A3MUTE_B14.819
AF-A4TEST_OSC0.000
AF-A5EXT_IN0.000
AF-A6EXT_SW-15.000
AF-A7LINE_OUT15.000
AF-A8EQ_OUT12.267
AF-A9CH4_REC0.000
AF-B1.2P5V5.000
AF-B10LINE_SW15.000
AF-B11EQ_IN15.000
AF-B12MECHA_IN15.000
AF-B13CH1_IN15.000
AF-B14CH2_IN15.000
AF-B15CH3_IN15.000
AF-B16CH4_IN15.000
AF-B17GND_B170.000
AF-B18GND_B180.000
AF-B3OSC1_SW0.658
AF-B4OSC2_SW0.658
AF-B5.6-15V-15.000
AF-B7GND0.000
AF-B8.9+15V15.000

2. DC operating point per mode

CheckSimulatedExpectedBasis
idle: CH1 REC COMM low0 V-0.01 to 0.5 V
idle: CH2 REC COMM low0 V-0.01 to 0.5 V
idle: CH3 REC COMM low0 V-0.01 to 0.5 V
idle: CH4 REC COMM low0 V-0.01 to 0.5 V
idle: LED1 off0 mA-0.01 to 0.1 mA
idle: LED2 off0 mA-0.01 to 0.1 mA
idle: LED3 off0 mA-0.01 to 0.1 mA
idle: LED4 off0 mA-0.01 to 0.1 mA
idle: LED5 off0 mA-0.01 to 0.1 mA
MECHA REC: CH1 REC COMM low0 V-0.01 to 0.5 V
MECHA REC: CH2 REC COMM low0 V-0.01 to 0.5 V
MECHA REC: CH3 REC COMM low0 V-0.01 to 0.5 V
MECHA REC: CH4 REC COMM low0 V-0.01 to 0.5 V
MECHA REC: LED1 off0 mA-0.01 to 0.1 mA
MECHA REC: LED2 off0 mA-0.01 to 0.1 mA
MECHA REC: LED3 off0 mA-0.01 to 0.1 mA
MECHA REC: LED4 off0 mA-0.01 to 0.1 mA
MECHA REC: LED5 on9.244 mA8.335 to 10.19 mAred LED from MUTE A, 330 ohm
MECHA REC + CH1: CH1 REC COMM high15 V13.5 to 15.01 VMC14081B AND of MECHA and the channel
MECHA REC + CH1: CH2 REC COMM low0 V-0.01 to 0.5 V
MECHA REC + CH1: CH3 REC COMM low0 V-0.01 to 0.5 V
MECHA REC + CH1: CH4 REC COMM low0 V-0.01 to 0.5 V
MECHA REC + CH1: LED1 on9.202 mA8.294 to 10.14 mAred LED from MUTE A, 330 ohm
MECHA REC + CH1: LED2 off0 mA-0.01 to 0.1 mA
MECHA REC + CH1: LED3 off0 mA-0.01 to 0.1 mA
MECHA REC + CH1: LED4 off0 mA-0.01 to 0.1 mA
MECHA REC + CH1: LED5 on9.2 mA8.294 to 10.14 mAred LED from MUTE A, 330 ohm
MECHA REC + CH2: CH1 REC COMM low0 V-0.01 to 0.5 V
MECHA REC + CH2: CH2 REC COMM high15 V13.5 to 15.01 VMC14081B AND of MECHA and the channel
MECHA REC + CH2: CH3 REC COMM low0 V-0.01 to 0.5 V
MECHA REC + CH2: CH4 REC COMM low0 V-0.01 to 0.5 V
MECHA REC + CH2: LED1 off0 mA-0.01 to 0.1 mA
MECHA REC + CH2: LED2 on9.202 mA8.294 to 10.14 mAred LED from MUTE A, 330 ohm
MECHA REC + CH2: LED3 off0 mA-0.01 to 0.1 mA
MECHA REC + CH2: LED4 off0 mA-0.01 to 0.1 mA
MECHA REC + CH2: LED5 on9.2 mA8.294 to 10.14 mAred LED from MUTE A, 330 ohm
MECHA REC + CH3: CH1 REC COMM low0 V-0.01 to 0.5 V
MECHA REC + CH3: CH2 REC COMM low0 V-0.01 to 0.5 V
MECHA REC + CH3: CH3 REC COMM high15 V13.5 to 15.01 VMC14081B AND of MECHA and the channel
MECHA REC + CH3: CH4 REC COMM low0 V-0.01 to 0.5 V
MECHA REC + CH3: LED1 off0 mA-0.01 to 0.1 mA
MECHA REC + CH3: LED2 off0 mA-0.01 to 0.1 mA
MECHA REC + CH3: LED3 on9.202 mA8.294 to 10.14 mAred LED from MUTE A, 330 ohm
MECHA REC + CH3: LED4 off0 mA-0.01 to 0.1 mA
MECHA REC + CH3: LED5 on9.2 mA8.294 to 10.14 mAred LED from MUTE A, 330 ohm
MECHA REC + CH4: CH1 REC COMM low0 V-0.01 to 0.5 V
MECHA REC + CH4: CH2 REC COMM low0 V-0.01 to 0.5 V
MECHA REC + CH4: CH3 REC COMM low0 V-0.01 to 0.5 V
MECHA REC + CH4: CH4 REC COMM high15 V13.5 to 15.01 VMC14081B AND of MECHA and the channel
MECHA REC + CH4: LED1 off0 mA-0.01 to 0.1 mA
MECHA REC + CH4: LED2 off0 mA-0.01 to 0.1 mA
MECHA REC + CH4: LED3 off0 mA-0.01 to 0.1 mA
MECHA REC + CH4: LED4 on9.202 mA8.294 to 10.14 mAred LED from MUTE A, 330 ohm
MECHA REC + CH4: LED5 on9.2 mA8.294 to 10.14 mAred LED from MUTE A, 330 ohm
TEST OSC 1 kHz: CH1 REC COMM low0 V-0.01 to 0.5 V
TEST OSC 1 kHz: CH2 REC COMM low0 V-0.01 to 0.5 V
TEST OSC 1 kHz: CH3 REC COMM low0 V-0.01 to 0.5 V
TEST OSC 1 kHz: CH4 REC COMM low0 V-0.01 to 0.5 V
TEST OSC 1 kHz: LED1 off0 mA-0.01 to 0.1 mA
TEST OSC 1 kHz: LED2 off≈ 0 mA-0.01 to 0.1 mA
TEST OSC 1 kHz: LED3 off0 mA-0.01 to 0.1 mA
TEST OSC 1 kHz: LED4 off0 mA-0.01 to 0.1 mA
TEST OSC 1 kHz: LED5 off0 mA-0.01 to 0.1 mA
TEST OSC 10 kHz: CH1 REC COMM low0 V-0.01 to 0.5 V
TEST OSC 10 kHz: CH2 REC COMM low0 V-0.01 to 0.5 V
TEST OSC 10 kHz: CH3 REC COMM low0 V-0.01 to 0.5 V
TEST OSC 10 kHz: CH4 REC COMM low0 V-0.01 to 0.5 V
TEST OSC 10 kHz: LED1 off0 mA-0.01 to 0.1 mA
TEST OSC 10 kHz: LED2 off0 mA-0.01 to 0.1 mA
TEST OSC 10 kHz: LED3 off0 mA-0.01 to 0.1 mA
TEST OSC 10 kHz: LED4 off0 mA-0.01 to 0.1 mA
TEST OSC 10 kHz: LED5 off0 mA-0.01 to 0.1 mA
EXT OSC: CH1 REC COMM low0 V-0.01 to 0.5 V
EXT OSC: CH2 REC COMM low0 V-0.01 to 0.5 V
EXT OSC: CH3 REC COMM low0 V-0.01 to 0.5 V
EXT OSC: CH4 REC COMM low0 V-0.01 to 0.5 V
EXT OSC: LED1 off0 mA-0.01 to 0.1 mA
EXT OSC: LED2 off0 mA-0.01 to 0.1 mA
EXT OSC: LED3 off0 mA-0.01 to 0.1 mA
EXT OSC: LED4 off0 mA-0.01 to 0.1 mA
EXT OSC: LED5 off0 mA-0.01 to 0.1 mA
LINE: CH1 REC COMM low0 V-0.01 to 0.5 V
LINE: CH2 REC COMM low0 V-0.01 to 0.5 V
LINE: CH3 REC COMM low0 V-0.01 to 0.5 V
LINE: CH4 REC COMM low0 V-0.01 to 0.5 V
LINE: LED1 off0 mA-0.01 to 0.1 mA
LINE: LED2 off0 mA-0.01 to 0.1 mA
LINE: LED3 off0 mA-0.01 to 0.1 mA
LINE: LED4 off0 mA-0.01 to 0.1 mA
LINE: LED5 off0 mA-0.01 to 0.1 mA
EQ high speed: CH1 REC COMM low0 V-0.01 to 0.5 V
EQ high speed: CH2 REC COMM low0 V-0.01 to 0.5 V
EQ high speed: CH3 REC COMM low0 V-0.01 to 0.5 V
EQ high speed: CH4 REC COMM low0 V-0.01 to 0.5 V
EQ high speed: LED1 off0 mA-0.01 to 0.1 mA
EQ high speed: LED2 off0 mA-0.01 to 0.1 mA
EQ high speed: LED3 off0 mA-0.01 to 0.1 mA
EQ high speed: LED4 off0 mA-0.01 to 0.1 mA
EQ high speed: LED5 off0 mA-0.01 to 0.1 mA
TEST OSC 1 kHz: Q501 released≈ 0 µA0 to 1 µA
TEST OSC 1 kHz: Q502 still holds OSC2 off305.1 µA100 to 1000 µA
TEST OSC 10 kHz: Q502 released≈ 0 µA0 to 1 µA
TEST OSC 10 kHz: Q501 still holds OSC1 off305.1 µA100 to 1000 µA
idle: Q503 gate-source (EXT off)-15 V-16 to -10 VD505 and R519 to -15 V
EXT OSC: Q503 gate-source (EXT on)0 V-0.5 to 0.7 V
LINE: Q504 base current1.393 mA1.26 to 1.54 mAR524 to the grounded switch, less R525's share
EQ high speed: EQ OUT-14.98 V-15.01 to -14.5 VEQ select open: R528 pulls the buffer to -15 V
AF pins by mode
AF pinnetidle (V)MECHA REC (V)MECHA REC + CH1 (V)MECHA REC + CH2 (V)MECHA REC + CH3 (V)MECHA REC + CH4 (V)TEST OSC 1 kHz (V)TEST OSC 10 kHz (V)EXT OSC (V)LINE (V)EQ high speed (V)
AF-A1.2MUTE_A4.9944.9714.9564.9564.9564.9564.9944.9944.9944.9944.994
AF-A10CH3_REC0.0000.0000.0000.00015.0000.0000.0000.0000.0000.0000.000
AF-A11CH2_REC0.0000.0000.00015.0000.0000.0000.0000.0000.0000.0000.000
AF-A12CH1_REC0.0000.00015.0000.0000.0000.0000.0000.0000.0000.0000.000
AF-A13SRCLK9.6789.6789.6789.6789.6789.6789.6789.6789.6789.6789.678
AF-A14LED44.1504.1284.1124.1124.1123.0914.1504.1504.1504.1504.150
AF-A15LED34.1504.1284.1124.1123.0914.1124.1504.1504.1504.1504.150
AF-A16LED24.1504.1284.1123.0914.1124.1124.1504.1504.1504.1504.150
AF-A17LED14.1504.1283.0914.1124.1124.1124.1504.1504.1504.1504.150
AF-A18LED54.1503.1063.0913.0913.0913.0914.1504.1504.1504.1504.150
AF-A3MUTE_B14.81914.81914.81914.81914.81914.81914.81914.81914.81914.81914.819
AF-A4TEST_OSC0.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
AF-A5EXT_IN0.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
AF-A6EXT_SW-15.000-15.000-15.000-15.000-15.000-15.000-15.000-15.0000.000-15.000-15.000
AF-A7LINE_OUT15.00015.00015.00015.00015.00015.00015.00015.00015.00014.98915.000
AF-A8EQ_OUT12.23112.25912.27512.25812.27412.25812.25612.25512.25412.254-14.982
AF-A9CH4_REC0.0000.0000.0000.0000.00015.0000.0000.0000.0000.0000.000
AF-B1.2P5V5.0005.0005.0005.0005.0005.0005.0005.0005.0005.0005.000
AF-B10LINE_SW15.00015.00015.00015.00015.00015.00015.00015.00015.0000.00015.000
AF-B11EQ_IN15.00015.00015.00015.00015.00015.00015.00015.00015.00015.000-15.000
AF-B12MECHA_IN15.0000.0000.0000.0000.0000.00015.00015.00015.00015.00015.000
AF-B13CH1_IN15.00015.0000.00015.00015.00015.00015.00015.00015.00015.00015.000
AF-B14CH2_IN15.00015.00015.0000.00015.00015.00015.00015.00015.00015.00015.000
AF-B15CH3_IN15.00015.00015.00015.0000.00015.00015.00015.00015.00015.00015.000
AF-B16CH4_IN15.00015.00015.00015.00015.0000.00015.00015.00015.00015.00015.000
AF-B17GND_B170.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
AF-B18GND_B180.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
AF-B3OSC1_SW0.6580.6580.6580.6580.6580.6580.0000.6580.6580.6580.658
AF-B4OSC2_SW0.6580.6580.6580.6580.6580.6580.6580.0000.6580.6580.658
AF-B5.6-15V-15.000-15.000-15.000-15.000-15.000-15.000-15.000-15.000-15.000-15.000-15.000
AF-B7GND0.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000
AF-B8.9+15V15.00015.00015.00015.00015.00015.00015.00015.00015.00015.00015.000

3. Test oscillators

0OSC1 OUT0.0TEST OSC (AF-A4)76.076.577.077.578.0
1 kHz oscillator, in V against ms; each trace on its own scale.
-10010OSC2 OUT-0.20.00.2TEST OSC (AF-A4)11.8011.8511.9011.9512.00
10 kHz oscillator, in V against ms; each trace on its own scale.
0EXT OSC IN (AF-A5)-0.50.00.5TEST OSC (AF-A4)252627282930
EXT OSC selected, 1 V at 400 Hz in, in V against ms; each trace on its own scale.
CheckSimulatedExpectedBasis
OSC1 frequency1010 Hz981.3 to 1042 Hzbridged T: C502, C503, R504, R505
OSC1 amplitude steady (60-80 ms over 40-60 ms)10.99 to 1.01
OSC1 amplitude at OSC1 OUT18.95 Vpp5 to 28 Vppset by the RD6.2EB limiter (reported)
OSC1 level at TEST OSC / OSC1 OUT0.046030.04371 to 0.04831C504, R507, C505, R508 into IC502 (R522)
OSC1 limiter divider0.02280.02257 to 0.02303R502 / (R502 + R503) into the + input
OSC1 limiter clamp13.05 Vpp12.44 to 13.75 Vppback-to-back RD6.2EB: 2 x (BV + VF), at about 1 mA
OSC1 THD at TEST OSC0.291 %0 to 5 %at the measured frequency (reported)
OSC2 held off while OSC1 runs≈ 0 Vpp0 to 0.05 Vpp
OSC2 frequency9976 Hz9813 to 10420 Hzbridged T: C507, C508, R512, R513
OSC2 amplitude steady (9-12 ms over 6-9 ms)10.99 to 1.01
OSC2 amplitude at OSC2 OUT23.26 Vpp5 to 28 Vppset by the RD6.2EB limiter (reported)
OSC2 limiter divider0.026840.02657 to 0.0271R510 / (R510 + R511) into the + input
OSC2 limiter clamp13.13 Vpp12.44 to 13.75 Vppback-to-back RD6.2EB: 2 x (BV + VF), at about 1 mA
OSC2 THD at TEST OSC0.4267 %0 to 5 %at the measured frequency (reported)
OSC1 held off while OSC2 runs≈ 0 Vpp0 to 0.05 Vpp
OSC2 level at TEST OSC / OSC2 OUT, VR501 at 0.50.024880.02348 to 0.02595C509, R515, C510, VR501 (25 kohm), R516 into IC502
OSC2 level at TEST OSC / OSC2 OUT, VR501 at 0.10.043240.04082 to 0.04512C509, R515, C510, VR501 (5 kohm), R516 into IC502
OSC2 level at TEST OSC / OSC2 OUT, VR501 at 0.90.017460.01648 to 0.01821C509, R515, C510, VR501 (45 kohm), R516 into IC502
EXT OSC to TEST OSC gain (EXT selected)0.73070.6933 to 0.7662C511, R517, R518 + Q503 on, into IC502
EXT OSC to TEST OSC leak (EXT not selected)≈ 00 to 0.01Q503 pinched off

4. REC command logic and the 555 clocks

051015CH1 REC COMM (AF-A12)051015CH3 REC COMM (AF-A10)01234
REC COMM outputs through the sequence, in V against s; each trace on its own scale.
05LED1, CH1 (AF-A17)05LED3, CH3 (AF-A15)05LED5, MECHA REC (AF-A18)01234
REC LED currents, in mA against s; each trace on its own scale.
510IC401 output510SRCLK (AF-A13)2000202020402060
S.R. CLOCK, in V against ms; each trace on its own scale.
CheckSimulatedExpectedBasis
IC401 (S.R. CLOCK) period18.68 ms18.34 to 19.09 msln2 (R412 + 2 R413) C408
SRCLK (AF-A13) high12.1 V11.74 to 12.46 VIC401 through R411 into C406
SRCLK (AF-A13) low1.809 V1.69 to 1.868 Vthe same RC: C406 never empties in a 9 ms low
IC402 (LED flash) period381.6 ms373.6 to 388.9 msln2 (R414 + 2 R415) C411
idle: CH1 REC COMM low0 V-0.01 to 0.5 V
idle: CH2 REC COMM low0 V-0.01 to 0.5 V
idle: CH3 REC COMM low0 V-0.01 to 0.5 V
idle: CH4 REC COMM low0 V-0.01 to 0.5 V
idle: LED1 off≈ 0 mA-0.01 to 0.1 mA
idle: LED2 off≈ 0 mA-0.01 to 0.1 mA
idle: LED3 off≈ 0 mA-0.01 to 0.1 mA
idle: LED4 off0 mA-0.01 to 0.1 mA
idle: LED5 off≈ 0 mA-0.01 to 0.1 mA
CH1 armed: CH1 REC COMM low0 V-0.01 to 0.5 V
CH1 armed: CH2 REC COMM low0 V-0.01 to 0.5 V
CH1 armed: CH3 REC COMM low0 V-0.01 to 0.5 V
CH1 armed: CH4 REC COMM low0 V-0.01 to 0.5 V
CH1 armed: LED1 flashes (peak)9.201 mA7.833 to 10.6 mA
CH1 armed: LED1 flashes (trough)≈ 0 mA-0.01 to 0.1 mA
CH1 armed: LED5 flashes (peak)9.198 mA7.833 to 10.6 mA
CH1 armed: LED5 flashes (trough)≈ 0 mA-0.01 to 0.1 mA
CH1 armed: LED2 off≈ 0 mA-0.01 to 0.1 mA
CH1 armed: LED3 off≈ 0 mA-0.01 to 0.1 mA
CH1 armed: LED4 off≈ 0 mA-0.01 to 0.1 mA
CH1 armed: LED1 flash period381.6 ms362.2 to 400.3 msfollows IC402 through the MC14011B NAND
recording CH1: CH1 REC COMM high15 V13.5 to 15.01 V
recording CH1: CH2 REC COMM low0 V-0.01 to 0.5 V
recording CH1: CH3 REC COMM low0 V-0.01 to 0.5 V
recording CH1: CH4 REC COMM low0 V-0.01 to 0.5 V
recording CH1: LED1 steady on9.202 mA8.294 to 10.14 mA
recording CH1: LED5 steady on9.2 mA8.294 to 10.14 mA
recording CH1: LED2 off≈ 0 mA-0.01 to 0.1 mA
recording CH1: LED3 off≈ 0 mA-0.01 to 0.1 mA
recording CH1: LED4 off≈ 0 mA-0.01 to 0.1 mA
recording CH1 + CH3: CH1 REC COMM high15 V13.5 to 15.01 V
recording CH1 + CH3: CH2 REC COMM low0 V-0.01 to 0.5 V
recording CH1 + CH3: CH3 REC COMM high15 V13.5 to 15.01 V
recording CH1 + CH3: CH4 REC COMM low0 V-0.01 to 0.5 V
recording CH1 + CH3: LED1 steady on9.166 mA8.262 to 10.1 mA
recording CH1 + CH3: LED3 steady on9.166 mA8.262 to 10.1 mA
recording CH1 + CH3: LED5 steady on9.164 mA8.262 to 10.1 mA
recording CH1 + CH3: LED2 off≈ 0 mA-0.01 to 0.1 mA
recording CH1 + CH3: LED4 off≈ 0 mA-0.01 to 0.1 mA
stopped, CH1 + CH3 armed: CH1 REC COMM low≈ 0 V-0.01 to 0.5 V
stopped, CH1 + CH3 armed: CH2 REC COMM low0 V-0.01 to 0.5 V
stopped, CH1 + CH3 armed: CH3 REC COMM low≈ 0 V-0.01 to 0.5 V
stopped, CH1 + CH3 armed: CH4 REC COMM low0 V-0.01 to 0.5 V
stopped, CH1 + CH3 armed: LED1 flashes (peak)9.166 mA7.803 to 10.56 mA
stopped, CH1 + CH3 armed: LED1 flashes (trough)≈ 0 mA-0.01 to 0.1 mA
stopped, CH1 + CH3 armed: LED3 flashes (peak)9.166 mA7.803 to 10.56 mA
stopped, CH1 + CH3 armed: LED3 flashes (trough)≈ 0 mA-0.01 to 0.1 mA
stopped, CH1 + CH3 armed: LED5 flashes (peak)9.164 mA7.803 to 10.56 mA
stopped, CH1 + CH3 armed: LED5 flashes (trough)≈ 0 mA-0.01 to 0.1 mA
stopped, CH1 + CH3 armed: LED2 off≈ 0 mA-0.01 to 0.1 mA
stopped, CH1 + CH3 armed: LED4 off≈ 0 mA-0.01 to 0.1 mA
idle again: CH1 REC COMM low0 V-0.01 to 0.5 V
idle again: CH2 REC COMM low0 V-0.01 to 0.5 V
idle again: CH3 REC COMM low0 V-0.01 to 0.5 V
idle again: CH4 REC COMM low0 V-0.01 to 0.5 V
idle again: LED1 off≈ 0 mA-0.01 to 0.1 mA
idle again: LED2 off≈ 0 mA-0.01 to 0.1 mA
idle again: LED3 off≈ 0 mA-0.01 to 0.1 mA
idle again: LED4 off≈ 0 mA-0.01 to 0.1 mA
idle again: LED5 off≈ 0 mA-0.01 to 0.1 mA

5. Power-on mute

024MUTE A (AF-A1.2)510MUTE B (AF-A3)012C603 (mute timer)01234
Power-on mute, in V against s; each trace on its own scale.
CheckSimulatedExpectedBasis
C603 at 1 s1.157 V1.134 to 1.18 V5 V x (R606 + R607) / (R604 + R606 + R607), tau = C603 x (R604 || R606 + R607)
C603 at 2 s1.811 V1.777 to 1.849 V5 V x (R606 + R607) / (R604 + R606 + R607), tau = C603 x (R604 || R606 + R607)
C603 at 3 s2.18 V2.142 to 2.229 V5 V x (R606 + R607) / (R604 + R606 + R607), tau = C603 x (R604 || R606 + R607)
MUTE B held before the release14.35 V13 to 15.01 VQ606 on, fed from C604 through D601
MUTE A off before the release≈ 0 V-0.01 to 0.5 V
MUTE B release time2.434 s2.293 to 3.047 sR607's tap reaching two VBE (1.15-1.30 V) on C603's charge
MUTE A on after MUTE B0.9777 s0.5 to 1.5 sQ605 needs ~6.5 mA of Darlington current (0.65 V across R609), Q607 only ~0.2 mA (R612)
MUTE A when running4.98 V4.8 to 5.01 V
MUTE B when running≈ 0 V-0.01 to 0.1 V
MUTE B re-asserted after power-off starts1.281 ms0 to 10 msQ607 loses its emitter supply, so Q606 turns on from C604; depends on the assumed 50 ms ramp
C603 emptied by Q6020.1371 V0 to 0.3 VC601 cuts Q601 off; Q602 discharges C603 through R605
MUTE B hold time constant1.136 s0.99 to 1.21 sC604 x (10 kohm load || R611)
time points after power-off54010 to 20000the unpowered board stays cheap to simulate (100 us maximum step)

Run it yourself

Download the KiCad project, open pb45e0a.kicad_pro in KiCad 10 and start the simulator (Inspect › Simulator). Its symbols, models and test bench are in the folder, so nothing else needs installing. The sheet's .op directive gives the idle DC table above; for a power-on run use .tran 100u 4 0 uic and probe AF-A13, the shift-register clock, or the + side of C603, the mute timer. The other scenarios add switch closures, LED loads and an EXT OSC signal that are not on the sheet.

← BQ-II manual, Section 10