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Note: please see comments and possible fixes before building this unit.
Most surface mount devices (except C9) are soldered onto one side of the circuit board. The other side holds C9, IC2 and T2. IC2 and T2 are mounted upside down, i.e. the plastic side of the package touches the board, and the metal tabs face away from it. IC2 (voltage regulator for the receiver battery eliminator circuit) rests flat on top of C9. Its three pins go through the holes in the board and are soldered to traces on both sides.
T2 lies parallel to IC2 on the other half of the circular board. Only one pin (gate) goes through to the other side of the board; the other two are soldered directly to the broad traces connecting to the negative battery lead and the negative motor terminal.
The throttle servo connector from the receiver is soldered in three places labeled "Impuls" (signal, or pulse), +5V (red connector in most receivers, supplies receiver power) and GND (usually black or brown wire).
The optional "free-run" diode D3 can be soldered directly to the motor terminals, or mounted in the holes in the PCB ("Motor -" and "Motor +"). The anode mark or band on the diode must be pointing towards the positive motor connection.
P1 is used to adjust the cut-off point of the motor.
| Part | Value or type | Package |
| IC1 | LM393 | SO-8 |
| IC2 | LM2940-5V | TO-220 |
| T1 | BC847 | SOT-23 |
| T2 | SMP60N03-10L or similar | TO-220 |
| D1 | LL4148 | SOD-80 |
| D2 | 4.7V Zener | SOD-80 |
| D3 (optional) | SB550 | NOT SMD! |
| P1 | 20k | SMD trimmer |
| R1 | 820 | 1206 |
| R2 | 470k | 1206 |
| R3, R6 | 33k | 1206 |
| R4, R8 | 1.2k | 1206 |
| R5 | 47k | 1206 |
| R7 | 22k | 1206 |
| R9 | 100k | 1206 |
| R10 | 15k | 1206 |
| R11 | 1M | 1206 |
| RG | 100 | 1206 |
| C1, C4 | 10nF | 0805 |
| C5, C6 | 100nF | 0805 |
| C7 | 22nF | 0805 |
| C2 | 2.2uF tantalum | 1210 |
| C3 | 1uF tantalum | 1206 |
| C8 | 4.7uF tantalum | 1210 |
| C9 | 10uF tantalum | 1812 |
According to Siemens data sheets BC847 is a silicon NPN audio frequency transistor with high current gain (typical hFE of 520 at 2 mA collector current and 5 V collector-emitter voltage), 330 mW power dissipation and about 50 V peak Vce and Vcb. It should be easy to find a suitable SMD replacement in the DigiKey catalog (e.g. Zetex BCX70KCT-ND).
SMP60N03-10L is an N-channel enhancement-mode logic level power MOSFET made by Siliconix. Maximum drain-source voltage is 30 V, gate treshold voltage is between 0.8 and 3 V, continuous drain current at 25 degrees Celsius is 60 A, and power dissipation at 25 degrees is 105 W. It should withstand up to 12 A without a heatsink.
LL4148 should be the same as 1N4148, a silicon small-signal diode. The optional SB550 is a fast switching type or a Schottky diode capable of 30V or more reverse voltage. Other acceptable types include BYV28 or MBRD650.
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