Can anyone suggest for replacement of Transistor SL100 for this kind of cuircuit? Please help me. I'm from Philippines.
I need your thoughts and favorable reply guys. Thank you.
Hi PH,
There is nothing special about transistor, T1, on your circuit board, or its function. Here is the data sheet for the SL100:
https://www.engineersgarage.com/sites/default/files/SL100_0.pdf
(1)
Transistor T1 equivalents
As LG shows in his post #9 link, there are many transistors that would do your job.
(2)
Transistor important characteristics
The only important characteristics for T1 your circuit board are:
(1.1) Transistor type: NPN silicon bipolar junction transistor (BJT)
(1.2) Case: T0-39 or T0-5
(1.3) Power (Ptot): at least 800 mili Watts (0.8 Watts)
(1.4) Collector current: at leat 500 mili Amps (0.5 Amps)
(1.5) Collector Emitter Voltage (VCE): at least 10V (most transistors would be at least 30V)
Just ask your local, or internet electronics store for a transistor to meet the above specification and they will fix you up.
As the transistor needs some heat sinking, according to your diagram, an all-plastic case transistor would not be suitable.
(2)
Some specific replacement transistors
(2.1) To use the existing heat sink you need a transistor with a TO-39 or TO-5 metal case: BFY50x, BFY52x, 2N3053x
https://www.farnell.com/datasheets/13478.pdf
(2.2) If you have the space, as mvs has suggested, fit a TO-126 plastic/metal case: BD139x,
https://www.fairchildsemi.com/datasheets/BD/BD135.pdf
(2.3) Or bigger TO-220 plastic/metal case: TIP31x:
https://www.fairchildsemi.com/datasheets/TI/TIP31C.pdf
(x after part number indicates that any suffix part will do. For example TIP31. TIP31A, TIP31B, TIP31C)
(3)
Recommended Transistors
The BD139 and TIP31 are the best choice if they will fit. I would think that the original transistor is a bit weak for driving a motor- that may be why it has failed.
(4)
T1 Base drive
The value of R3 should be reduced from 1K to around 220 Ohms as Les has suggested (150 Ohms) to put more current into the base of transistor T1, and ensure it is turned on fully. Paradoxically, this will help protect transistor T1.
(5)
Protection diode
Also as Les recommends, a diode should be connected across transistor T1 (cathode to collector and anode to emitter) to protect the transistor from negative voltages generated by the inductance of the motor. A 1N4oox diode would be suitable or any other 1A or more 10V or more rectifier diode. As the supply line is only 5V, a positive catching diode should not be needed.
(6)
Decoupling
The circuit also needs some decoupling across the 5V supply line: 470 micro Farads minimum aluminum electrolytic capacitor in parallel with a 100 nano Farad minimum ceramic capacitor. Both capacitors should have a voltage rating of at least 7V. The electrolytic capacitor must have its positive terminal connected to the 5V supply line and not the other way around. It does not matter which way around the ceramic capacitor is connected, because it is not polarised.
spec