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  1. Alec_t

    Old Grundig TV repair

    That failed capacitor is marked 'X2', so a replacement should also be an X2 type.
  2. Alec_t

    New LTSPICE Version XVII

    It's claimed to be up to 30% faster than the old version. I've been using it for a few weeks now, but haven't found any noticeable speed increase. I guess it depends how complex the circuit being simulated is.
  3. Alec_t

    Op Amp 741

    If the meter is anything like this one, it covers a frequency range of less than one octave. Does yours? If so, it would probably respond unambiguously to a square-wave input. A square-wave at high voltage would be much simpler/cheaper to generate than a sine-wave.
  4. Alec_t

    Op Amp 741

    Can you post a link to this frequency meter? I'm surprised it needs a 115V input and 7W.
  5. Alec_t

    Op Amp 741

    Googling "741 amplifier schematic" gives lots of hits. Be aware, though, that the 741 is an out-dated opamp with a poor frequency response and limited input/output voltage ranges.
  6. Alec_t

    Ceiling fan blades wont spin freely

    Try to work some oil into the bearings.
  7. Alec_t

    Capacitor Voltage Divider

    To pass 6A at 50/60Hz would require a low ESR (equivalent series resistance) capacitor of at least 85uF with a working voltage of at least 350V AC (for a 240V supply). That wouldn't be cheap or easy to source.
  8. Alec_t

    Capacitor Voltage Divider

    A PWM circuit running from 15V with a 8/15 mark/space ratio (duty-cycle) would give you an average of 8V. The long thermal time constant of a Peltier does the averaging. It's a doddle to control the duty-cycle (and hence average voltage) with the Arduino.
  9. Alec_t

    Capacitor Voltage Divider

    What is the maximum rated voltage of the Peltiers?
  10. Alec_t

    H-Bridge motor driver not working properly

    Correct.
  11. Alec_t

    How to remove solder from plated-through holes?

    Tried the add-more-solder approach: no joy. The problem seems to be that with very small holes the solder's surface tension within the hole exceeds the capillary tension that the wick can provide or the sucker can overcome. Tried a 25W with cylindrical tip and a 15W with chisel tip. Adjacent...
  12. Alec_t

    How to remove solder from plated-through holes?

    I have a double-sided pcb with plated-through holes occupied by component legs. I removed a dead 16-pin DIL IC by chopping off its legs, then unsoldered the legs individually. Use of a solder sucker and solder wick has failed to clear the vacated holes. Any suggestions how to clear them so that...
  13. Alec_t

    Capacitor Voltage Divider

    Resistors would waste 42W of power if you need to drop from 15V to 8V at 6A. What you need is a switched-mode power supply (buck converter). Cheaper to buy one than build one.
  14. Alec_t

    H-Bridge motor driver not working properly

    Because the scope negative is grounded you would be shorting pin 5 or 8 to ground. The chip won't like that.
  15. Alec_t

    Capacitor Voltage Divider

    That circuit works only if you draw no current from it. Here's what happens as soon as a load draws current :-
  16. Alec_t

    Variable speed water pump controller

    That web-site is blocked because it shows up as 'drugs and criminal skills' according to my ISP!
  17. Alec_t

    A ferromagnetic metal detector

    I'd be very surprised if it did. There's so much interference all around us at that frequency and its harmonics. Why not go for a much higher frequency where it would be easier to filter out interference?
  18. Alec_t

    Secure Brief Case - Electronically activated lock

    Like this? I can't help feeling that all the high-tech parts of the briefcase, such as the tablet, will make it an even more tempting target for thieves :D.
  19. Alec_t

    LTSpice installation under w10

    It installed fine on my Lenovo Z50-70 Win10 laptop too.
  20. Alec_t

    H-Bridge motor driver not working properly

    I think you have neglected the inductive reactance of your coil. That will present an impedance dependent on frequency. What is your PWM frequency? Does your coil have a DC resistance of 30Ω and an inductance of 0.15H, as per the link? :eek: Why? That may have fried the chip, or if you're lucky...
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