1. SMPS Lover

    SMPS Transformer noise and Low output voltage

    Hello, i have an issue with a 12v30A PSU: low output of 4v instead of 12v, SMPS transformer noise like low frequency issue. No short element in the secondary, RT/CT of tl 494 within specs, but i suspect the capacitor at VCC of TL494 : it is only 10mF and has only 7.5V. The DC output voltage...
  2. taharat

    12V 2A power supply with 1M ohm resistor, 1uF 250V capacitor and 1N5408 diode

    Hello everyone. I have seen many videos on YouTube where they built a capacitor based 220V AC to 12V DC power supply. But those were not sufficient for my project. I am eager to build a 12V 2A power supply where the input will be 220V 50 Hz using the following components: 105K 250V ceramic...
  3. C

    Cube Capacitor Problem

    Got anxious about it and I don't know how to start solving this. Sorry for the bad drawing.
  4. tlemsalim

    Dielectric permittivity measurement of solid materials using capacitors

    Hi, I am currently doing some research work on different ways to measure permittivity of materials. In particular, I want to measure the permittivity of FR4 materials of PCB, and of an aluminium oxide block of approximately 0.5 cm^3, at 2.45 GHz. One idea I want to explore is how to measure...
  5. P

    Blown Inductors on a Dell Laptop Board

    Hello everyone, first thread here, I have cracked open a Dell XPS13 9350 that I've diagnosed the motherboard being dead. It's my mothers old laptop. I figured this would be a good chance to learn more about the micro parts on a board. Upon taking it apart, I found some blown inductors (atleast...
  6. M

    AC voltage rating of capacitor?

    I have a doubt regrading the Ac voltage rating of the capacitor. I am using a capacitor which is rated for 630V DC. I want to know the Ac voltage rating for this capacitor. If anyone have come across this please add some suggestions...
  7. CobraL0rd

    Old Amplifier reeks a burned smell and smokes after being turned on

    My mom has an old ~40 year old audio amplifier LUXMAN L-210, that hasn't been turned on for about a decade. I found some time the other day and turned it on to see whether it's working and how it's performing. So it did turn on and seemed to work (I have radio tuner, cassette player and disk...
  8. I

    MC2100 Rev B - Issues (Treadmill Main Board)

    MC2100 RevB- I have aquired 3 of these boards (dang Proform) over time and now at a stage that all 3 have their own weird issues. I tried replacing MOSFET IR260N on two of the boards in hopes of fixing it, as I don't have a bench setup to diagnose exactly what could be the issue, I have switched...
  9. E

    Chaos generator MOSFET, how does it work?

    The circuit in the picture is a chaotic generator formed from MOSFETs as opposed to op amps from the usual chaos generators. How does it all work exactly? Whilst I have knowledge of how MOSFETs work and such, the connections etc are hard to understand what they all do completely. In-depth...
  10. Albojk

    Understand capacitor value

    Hi all, recently I accidentally broke my pc keyboard with a usb hub overvolted. I found a burnt capacitor and I would like to change it before buying a new keyboard. I think its the same as another on the same board. Can you suggest me a similar capacitor I can buy? I am not able to understand...
  11. S

    RMS Voltage change of MLCC Capacitor with Frequency

    Hi all. So I know that the impedance of the capacitor changes with frequency. However, stumbling across a document by KEMET and their new stacked MLCC capacitors which allow higher ripple current, https://www.mouser.co.uk/datasheet/2/212/1/KEM_C1105_KONNEKT_KC_Link_C0G-1855982.pdf There are...
  12. Rahul Sharma 1

    which capacitor should I chose ceramic or tantalum

    I am having 2.8V on board regulator which is supply voltage to the EEPROM. Do I need to have tantalum capacitor near the EEPROM. Can Anyone please help me with what happen if I replace tantalum capacitor with ceramic capacitor. Thanks rahul
  13. M

    How Did This Circuit Go So Wrong?

    I built this circuit based on the examples in the datasheet. It worked. Transistor Q3_1 is BUJ100LR,412Bipolar Transistors - BJT Bipolar Transistors - BJT Trans GP BJT NPN 400V 1A 3-Pin https://www.mouser.ie/datasheet/2/848/BUJ100LR-1846655.pdf C2_1 is 4.7uF Tantalum Capacitors 20V...
  14. J

    Doubt on which type of film capacitor to use

    ']https%3A//i.ibb.co/wCPxShQ/IMG-20200826-174720.jpg[/img]'] Hi. I have a PCB which has a faulty Panasonic ECQ-UL polyester film capacitor that needs replacing. The capacitor is used as a capacitive power supply and the board goes haywire when this cap becomes faulty. The board is from a...
  15. Adrienboub

    VHF oscillator circuit w/ large frequency range and change according to capacitance value

    Hello, It's my first post. I'm new in electronics fields. I'm french and my english is not very good, excuse me. I want to make a VHF oscillator(~ 30 MHz) that his frequency can change with the value of the capacitance. I found in an another post the RF2506 which seems to works but it's...
  16. P

    Finding the Size of Inductor and Capacitor

    Hi, i have calculated the L and C value for filter circuit for Three phase inverter, now i would like to know the size and weight of the filter circuit for the L and C value i have calculated. Can anyone help me on how to do this ? Thank you. Raj
  17. K

    Diagnosing/repairing a Laptop motherboard?

    Hey guys! First time posting here! I have an Alienware 17 R3 laptop that I picked up broken to see if it was repairable (I like learning new skills). All signs point to a short on the motherboard, I plugged in the charger and the blue LED on the charger cable goes out immediately if I attempt to...
  18. Analog Ground

    How were "Outside Foil" connections on vintage foil capacitors documented?

    In another thread, I learned about the "Outside Foil" designation on one lead of some vintage foil capacitors. How was this connection specified on schematics or other documentation? Here is an example of the indication.
  19. P

    Polarized Capacitor in Reverse Direction

    What is the purpose of that capacitor there?
  20. John Czerwinski

    Correct replacement electrolytic capacitor.

    Confused on choosing the correct replacement electrolytic capacitor. For example, on an Atari AR I board (built in the early 1980s), the parts list calls for two (2) 3300 uf Aluminum Electrolytic Fixed Axial-Lead 35V. The original capacitor PHYSICAL size are relatively large. When you go on...