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  1. B

    Meaning of codes on two transistors.

    This is my first post. I have a Marantz PM-66SE KI. The left speaker and headphone outputs are almost completely silent. This might be due to dead transistors. I opened the unit and I noted the codes on the transistors screwed onto the heat sink. They are A1265N R 7K and C3182N R 8A I...
  2. N

    Microwave frequencies emitter circuit

    Hello, For my project I need to build a variable frequency emitter, with a frequency between 100MHz and 3500Mhz. I saw some simple RF circuits on the Internet but I don't think they can reach such high frequencies. Here is a circuit I've found : I don't need to transfer any information, so...
  3. B

    IR Circuit question

    I'm trying to make a simple IR circuit that energizes a coil when the detector "sees" the beam (refer to attached schematic). The problem is when the everything is active, I have almost no current at the coil. Why am I losing so much current? I suspect it's because the base of the NPN transistor...
  4. L

    Enable Pin vs Shutdown Pin

    Hello Everyone, I have a problem here... I am designing a board that I need a low voltage cutoff for... I want to use the Enable pin to do this... I have the circuit designed for a shutdown pin, but this is the opposite of the enable pin, right??? Here is my design in LTSpice... So here are...
  5. K

    Need help interpreting an old circuit diagram: Transistor and RF Transformer

    I will start by apologizing for asking what may be very simple questions; I am a scientist who has built some simple circuits before, but I am not by any means an expert in circuitry. I am trying to build a simple circuit based on a diagram in a modern laboratory textbook, but the textbook's...
  6. 1

    TO-247 bent pins

    Long-short question: I am working at a new project, a lab power supply. I used some TIP3055 for this project. Those TIP3055 were recovered from another project and the pins were a little bit short. I was forced to bend them from near the plastic case to make them fit to the new project PCB...
  7. F

    Resistor Parasitic Capacitance and RF Operating point

    As a reference to my question; I know that a 10K ohm resistor that has a parasitic capacitance of .3pF at 200MHz will have a actual impedance value of 2.564K ohms. If this resistor is used in a bias network for an RF amplifier, how does this shift in resistance effect the RF operating point...
  8. S

    Bipolar transistor

    Hello everyone, I have a little issue here. I know it's not really hard but it has been a moment since I've worked with circuits like this and transistors, so I can't figure out this circuit... The question is: In DC analysis, calculate the bipolar transistor's voltages Vb, Ve, Vc. Deduce the...
  9. sr13579

    How to make a simple oscillator with transistor and Capacitor?

    I provided a circuit which should discharge at a specific time. But this circuit is not working as an oscillator. How should I make circuit which will give me oscillation?
  10. mading2018

    Temperature with heatsinkcalculator software

    Hello :happy:, I have in the recent days tried to simulate the temperatures levels in a charger (AC/DC-module) in a Heatsinkcalculator software: https://www.heatsinkcalculator.com/version-2-1/demo-calculator.html Based on the power losses calculations for half-bridge, where we have two MOSFETs...
  11. T

    Transistor tester won't start self test mode

    I've got a transistor tester 1.12k version and it says it's not calibrated. When I connect the 3 different pins together it asks if I want to run self test mode. I press the button within 2 seconds (as the manual suggests) but instead of calibration menu it just makes a single test and displays...
  12. sr13579

    How am I supposed to get a plot from this code on WeSpice(NGspice) engine?

    There is the code ’npn transistor vbias 3 0 dc 5v vs 1 0 dc 0v rb 1 2 20k rc 3 4 2k q 4 2 0 mynpn .model mynpn npn (BF=175 IS=1e-17 VA=75 BR=2) .dc vs 0 5 0.5 .plot dc v(3) -i(vbias) .end ’ But the output is showing a negative going down. How to get the graph of the plot with this app called...
  13. F

    About the function of transistor

    Here i attached a simple wireless power transmission circuit. What is the function of transistor here?
  14. Ginger FerrroChrome

    Newbie trying to replace a transistor (Pioneer 1203 31, Q409)

    Hello! 'Name's Forrest! Or Ginger, whatever you prefer. So, I'm pretty new at electronics repair, I've replaced a couple of laptop modules and put new belts on all of my cassette players, but I'm just now, for the first time, trying to soldier a component on a PCB (ironically I broke it trying...
  15. S

    Logic Buffers using discrete components

    Hello, If the digital output (LVCMOS 3V3) is heavily loaded , we may need to use buffer to meet Vih & Ioh (output high current) level of the receiver circuit. I prefer not use the stand-alone Buffer IC's . Can anyone guide me to design my own buffer circuit based on Transistors ?? Thanks Antony
  16. I

    Frequency Response Heterojunction Bipolar Transistor

    I have a project, first i need to find a circuit to Analyse/study the Frequency Response of Heterojunction Bipolar Transistor. Then simulate that circuit on SPICE (i'am using Orcad Cadence). Can someone help me finding a circuit as mentioned above???, I'm having difficulties finding one. Any...
  17. X

    Typical Application Connection IRAMX20UP60A

    Looking into the datasheet of the IRAMX20UP60A, I found a typical application connection which I am trying to understand. I attach a picture of the application circuit. The part inside the black square is what I don't understand. As far as I understand, if a low signal goes into the base of the...
  18. throbscottle

    NOS Transistor with brittle leads

    Happy Thursday everybody! I managed to get what is probably a genuine Toshiba 1996 2SA1302 with green epoxy, to repair a PA, and started bending it's leads to match the original which have a semi-circle bent into them, presumably to allow for thermal expansion. They creaked and crackled a bit...
  19. Y

    PNP Transistor - base voltage higher than collector

    Hi guys, Is it ok for the base voltage driving a PNP transistor to be higher than the collector voltage? I'm trying to throw the input to a HS088 doorbell board (see attached) high from a microcontroller in place of the button shown on the schematic - have been testing with Arduino UNO in this...
  20. E

    Class D amplifier for arduino

    I was playing about with transistor amplifiers nd I built this class D amplifier intended for use with the arduino ( or any other microcontroller) https://siliconjunction.wordpress.com/2017/02/28/class-d-amplifier-for-the-arduino/ Thanks Matt!
  21. A

    Transistor with resistance controlled by the amount of input power

    Hi, I am modding my computer motherboard and I have a RGB led strip header. But the fact is it can only supply 1 Amp of current through the 4 pin header. I want to be able to use a variable resistor to control a 12v line straight form my power supply that can provide power for a bigger LED that...
  22. CBB9

    Audio Triggered Switch Help

    I'm hoping someone here can help lead me in the right direction on an experiment of mine. In my car I have an automatic starter that includes a wire that when given the 12v negative connection will trigger the automatic starter. What I would like to do have this negative connection activated...

    Failed deWalt battery charger

    Got this charger given to me if it was worth repairing. I found both transistors shorted to zero ohms across all terminals and the resistor blown open circuit. See the hole in the yellow band. Don't know what caused it but I reckon it is a throwaway.
  24. Clarkdale44

    What are the alternatives i can use for SL100 Transistor and BT44 Triac?

    Hello I am thinking of building the below circuit but i am short on components. I have all the others except SL100 transistor and BT44 triac which i can't seem to find in any local store. If anyone can tell me what alternative components i can use for these two then please let me know i would...
  25. A

    Controlling voltage to a load with a single battery..

    Seems like a simple question, I have several PC fans (12 V, 1.35 A), all in separate loops and powered by a 12 v battery. The fans are wired to transistors being used as switches. My issue is that I don't want the transistor to supply 12 V of power, I want to immediately and always supply the...

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