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  1. dorke

    Help with modification of radio Sony ICF-SW35

    I would start with measuring the DC voltage on pin 7 relative to GND. Is it +B(4.1V) or 2.4V ? (the schematics is ambiguous here ) Next, use a low current(2mA) high efficiency LED . To get a 2ma current using the voltage measured on pin 7 and the LED parameters, Calculate the value of the...
  2. dorke

    Scraped component on PCB - is it likely to be ok?

    Did you buy this as a "new" part? If you did, I would ask for it's replacement.
  3. dorke

    Technics turntable's stylus specs required

    Hello, Photos of the cartridge ,preferably with part number may help. In this case I would replace the whole cartridge+needle,the cartridge should be according to one of the common standards. Looks like this TECHNICS SL-BD20 takes a P-mount type .(chose one that fits your budget from about...
  4. dorke

    Distorted audio on an old transistor radio cassette

    The VT2 -VT3 configuration pair is a differential amplifier ("long tail"). It has 2 inputs : (one is used for feedback of the output through R31 to TR3 base), and 1 output : to feed the final stage from TR2 collector through C25. You may think of it has a "simplified" op. amp.
  5. dorke

    Long duration timers - Notes for beginners

    The 555 is very much alive and kicking. It still has a long way to go before being obsolete. I think it will be around for as long as people are willing to use it, that may be for decades...;)
  6. dorke

    Long duration timers - Notes for beginners

    @peterlonz, Some more points are: 1. Is there a need for a variable "time interval"'or is it fixed/small number of different intervals ? 2. What is the accuracy required ? 3. Is there any uC/uP in the system? If there is,using it is the cheapest way to go.
  7. dorke

    Long duration timers - Notes for beginners

    @kooth , What " game"? Is this a software game on a "platform" like PC or Smartphone etc. ? If it is you can generate any timing you need via software. Looks like there is no real requirement for accuracy,thus a crystal osc. solution isn't a must.
  8. dorke

    Visonic powermax complete lost codes

    Welcome to EP. Try contacting Visonic support here. They may give you the best help for their products.
  9. dorke

    Resistor

    110 ohm (or about) is fine for "small" batteries like the ones shown in the video.
  10. dorke

    4020 divided outputs

    Well ,your circuit is wrong. Pins 4,8 of the 555 should be tied directly to VCC (not through R5)! Please provide all values of resistors and capacitors.
  11. dorke

    4020 divided outputs

    Welcome to EP. The problem is very likely not related to the 4020. Most probably it is related to the 555 circuit. What is the purpose of R5 ? Please provide all values of resistors and capacitors.
  12. dorke

    electronic schedule of a 4 bits adder

    Like @Harald Kapp noted we are talking about the same thing and I probably should have said "1 bit". In the traditional learning of adders there is another step: Creating a 1 bit Half adder. From that you create a 1 bit full adder. And then use it to create n -bits adders. This link can be of...
  13. dorke

    SAY WHAT!?!?!?!?

    That is what I call creativity! Self made welder
  14. dorke

    Voltage Testing Question

    Welcome to EP. I'm assuming you are talking about a non-LED screen. In this case You can cheek the input voltage of the high voltage inverter,not a problem(low voltage). I wouldn't try to check the inverter output (very high voltage) directly.
  15. dorke

    electronic schedule of a 4 bits adder

    Welcome to EP. You are writing under "Electronic projects", does it mean you need to implement the circuit in the smallest, cheapest, easiest way? If so, you can use the 74XXX283 IC for that. If however your purpose is learning: 1. You could use the "head in the wall" approach of a truth table...
  16. dorke

    Why don't I get a Sine wave?

    The definition of a pure sine wave is clear. You need to define the amplitude and frequency(phase). In practice sine waves are not pure , they have distortions(i.e the deviation from purity). That is measured in THD (Total Harmonic Distortion) and noise. Sometimes refereed to as spectral...
  17. dorke

    T3J81 (Zener Diode ?)

    Did you diagnose your generator? You my find these videos(and many others) helpful. test1 test2
  18. dorke

    T3J81 (Zener Diode ?)

    Replacing a simple diode with a Zener isn't a good idea at all. For a simple diode ,the reverse mode wouldn't have the avalanche breakdown(in a well designed circuit,i.e it's reverse breakdown voltage should be higher than the reverse voltage in the specific circuit). Hence in reverse mode it...
  19. dorke

    T3J81 (Zener Diode ?)

    Lets start from the beginning. You have a generator that spins but doesn't put out voltage. You want to fix it and,suspect the AVR board is at fault. Have you verified that the brushes are good ? Have you checked the windings? BTW,if the diodes are fine leave them be they are not the cause...
  20. dorke

    T3J81 (Zener Diode ?)

    The 2 SCRs are 6A/600V,(Teccor -now days Littlefuse, case should be T0-220 or TO-202). They look to be connected to the diodes like shown below. The unknown diode looks to serve the purpose of protection . Why do you think they are defective? Is any of them shorted or open in both directions...
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