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  1. D

    Kenwood TS 830S

    Was the original cathode R a 2W R. Some designs in RF amps use lower wattage Rs to act as safety fuses. Regards, Dana.
  2. D

    Circuit clarification

    Its basically a Low Pass filter to remove switching noise generated by buck. Regards, Dana.
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    The emitter has a higher potential than base ! How?

    http://web02.gonzaga.edu/faculty/talarico/EE303/HO/BJTPhysics.pdf Voltage Contolled Current Source - Device physics says its electrostatic fields controlling electron behavior. Regards, Dana.
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    LED Array question

    A rough look at matching. The V source offset in D1 leg swept from -.1V to +.1V. Basically simulating a nominal diode Vf from +1.6 to +1.8V. As you can see dramatic sharing unbalance at extremes of 100 mV between diodes. The sum of current also shows T swept from 20 C to 50 C Regards, Dana.
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    The emitter has a higher potential than base ! How?

    Bipolar transistor is a V controlled device - But we find using a current based model easier to calc bias and operating point values. Regards, Dana.
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    LED Array question

    Here is an analysis of standard diode current sharing, general principles apply as well to LEDs. https://www.st.com/resource/en/application_note/an4381-current-sharing-in-parallel-diodes-stmicroelectronics.pdf Also here is discharge characteristic for 9 V Alkaline cell...
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    LED Array question

    No "right" answer here because : 1) If LEDs all from safe lot they could have some level of matching. 2) LEDs various lots would be worse case, possibly resulting in 1 LED taking way too much current and burning out or shorting. Then that cascades\ into next parallel LED with a lower Vf hogging...
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    still suffering with a bridge rectifier overheating

    I see what looks like poor or cracked solder joints - Regards, Dana.
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    Why Raise Capacitance in Smoothing Caps?

    If you raise cap values : 1) Time to discharge when powering off increased. 2) Surge current on power up increase. More stress for other components. 3) Ramp up time at power on increased. Regards, Dana.
  10. D

    what mosfet to use for an induction heater

    A quick and dirty way of part selection go to digikey, and use the filter controls to filter to package, various voltages (threshold, breakdown), currents, and then pick a couple of datasheets to look at. This way you know production status as well, even inventory level at digikey. Generally...
  11. D

    what mosfet to use for an induction heater

    Use MOSFET to do what ? What are the ratings of the induction heater you are trying to design. Your schematic.....? Google "induction heater schematic", plenty of circuits with part numbers. Regards, Dana.
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    alternating LED flasher using 12Vdc supply and 555 timer

    Protect the circuit from load dump - https://m.littelfuse.com/~/media/electronics_technical/application_notes/varistors/littelfuse_suppression_of_transients_in_an_automotive_environment_application_note.pdf Also consider using a dual 555 timer -...
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    alternating LED flasher using 12Vdc supply and 555 timer

    https://www.instructables.com/simple-alternate-LED-flashing-using-555-timer/ https://mechatrofice.com/circuits/555/led-flasher-circuit Regards, Dana.
  14. D

    reed switch and tiny motor NO arduino

    555 timer solution with added transistor to drive relay (there are relays the 555 can drive directly, make sure flyback diode is included in circuit) -...
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    Pitcher to Catcher speaker

    An old technique for something like this is to add an inaudible signal to the audio stream, and detect it on the other side to trigger its player. Often used was a PLL on the downstream side of the added trigged signal in the source player. Classic was a 567 PLL tone detector...
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    4 Digit 7 Seg LCD Display Datasheet

    https://www.maximintegrated.com/en/products/power/display-power-control/ICM7211.html Regards, Dana.
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    TFT Screen problem (Toshiba TECRA 730CDT)

    Do you have a good magnifying glass to look at soldering and flat ribbon connectors ? Good lighting a must when you do it. Cracks in soldering joints, oxidation......bits on detritus inside flat ribbon female connectors. A fine wire brush to clean connectors (the ones you can access). Gentle is...
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    TFT Screen problem (Toshiba TECRA 730CDT)

    Long shot, but sure looks like a lost ground connection or power supply problem causing 50/60 Hz modulation of a timing input......just a thought. Regards, Dana.
  19. D

    Building a 4 poles filter

    I presume this is the end application ? https://ac0c.com/attachments/ac0c_Intro_to_Roofing_Filters__cadxa_6_oct_2011.pdf Regards, Dana.
  20. D

    Building a 4 poles filter

    Here is a design tool. https://rf-tools.com/lc-filter/ Do you have the crystal elements ? The schematic you show is probably 8'th order or higher due to them. You also do not give all the specs (including loss) needed - Does it have to be linear phase ? Regards, Dana.
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