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  1. ramussons

    Need circuit for sine-to-square/sawtooth generator

    A sine wave through a Comparator will give a Square Wave. A Square wave through a Modified Opamp Integrator will give a sawtooth. Both these will give the required output (+/- 12VDC @ 1.0A) when fed to a Complimentary Power output stage.
  2. ramussons

    Replacement pcb mount nicd battery

    Or you may have to fabricate using 3 of these https://www.ebay.co.uk/p/725500061
  3. ramussons

    Replacement pcb mount nicd battery

    Photo please.
  4. ramussons

    Blown SoundCard Input

    Shorting the Mic Input should cause no harm. Something else has happened, a co-incidence. Or that shorting involved some external voltage feed.
  5. ramussons

    2N2222 questions

    If that 2N2222 is being used as a switch, you can safely pass 800mA through its collector.
  6. ramussons

    Replacing electrolytic cap with non-polarized a mistake with tube radio?

    Equipment using vacuum tubes as rectifiers do not have a "surge" in the true sense since the heaters take time to warm up, which in turn limit the onrush current.
  7. ramussons

    Device powered by computer usb port but not USB phone charger

    There is a "chip" in the box. How did you confirm that it is an Stand Alone amplifier?
  8. ramussons

    Replacing electrolytic cap with non-polarized a mistake with tube radio?

    Having seen quite a few valve radios in the old days, this schematic is a bit strange. The complete HV current flows through one half of the rectifier heater! Logically, it will mean that if there is any additional HV current (due to leaky capacitors or over driven tubes....), that section of...
  9. ramussons

    Device powered by computer usb port but not USB phone charger

    Maybe the computer does the amplification part, the device maybe only a peripheral.
  10. ramussons

    help on computer SMPS repair

    I doubt very much that the fault in in the PSU. It IS MORE LIKELY be a component failure in the Motherboard.
  11. ramussons

    Help using NPN transistors as a switch

    Your sketch mentions a LED and it looks like one. Such LED's drop 1 to 3 volts, and hence a current limit is necessary. The data sheet mentions 5 volts and 30 volts. But there are conditions specified. data has to be read in full. If your 12 volts LED lamp can work directly across 12 volts...
  12. ramussons

    Glass encased component with 2 power diodes held close

    It may be a Filament Bulb acting as a current limiter. It will also be an indicator to inform the battery status: bright glow -> charging; dim glow -> charge complete.
  13. ramussons

    What signal required to create 30Hz - 100 Hz frequencies

    ".... 30hz -2.5Ghz frequency 15 feet away..." Did you say 30 Hz? o_O To start with, An Antenna array covering a few hundreds of square kilometers. :D
  14. ramussons

    Help using NPN transistors as a switch

    The "-" of 5 VDC get connected to the "-" of the 12 VDC. BUT the present setup will give you a burnt LED, and a damaged Transistor. Hopefully, your DC power supplies will be safe. The right way: Common the -ve of both the voltage ( 5 and 12 Volts) "transformers". Make sure that they are NOT...
  15. ramussons

    P=I^2R formula confusion from book

    The first example refers to Power in terms of Current and Resistance. I^2 * R gives the relationship. Just note that Power is Proportional to Square of Current. In the next page, the examples are about bulbs with various powers and their resistances. The main factor here is not the Current, but...
  16. ramussons

    Electronic Siren

    Thank you.
  17. ramussons

    Electronic Siren

    I remember building a 2 Transistor Siren - Not a 2 tone version, but one that ascends in pitch to a max, and then descends to a very low frequency. This was in the 70's, from a circuit in Popular Electronics (if I recollect correctly). I have gone through the available archives of PE, but not...
  18. ramussons

    Help to revive damaged Vivo Y21 mobile phone

    Why not try an authorised service centre?
  19. ramussons

    PREAMPLIFIER QUESTION BPA-100S Logitek PREAMP

    Does this help? http://www.usedprice.com/items/pro-sound/logitek/pro-preamplifier/bpa100s-345367.html
  20. ramussons

    Resistor value help

    very likely 0.22 Ohms, 10%
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