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  1. Audioguru

    Finding a good soldering iron....

    My 63/37 solder has a flux core so I have never needed and I have never used separate flux except when I soldered together some copper water pipes with a butane torch, 60/40 solder and acid flux from a can. I have never seen a Fry's store so I looked it up. They sell many products. I buy...
  2. Audioguru

    220v speaker problems

    A stepup transformer is not needed because 240VAC is in all USA and Canadian homes.
  3. Audioguru

    Finding a good soldering iron....

    I have some Name brand 60/40 solder and it is horrible. 63/37 solder is much better. Look up eutectic solder in Google.
  4. Audioguru

    Fm receiver circuit .

    An amplifier oscillates when it has positive feedback. Transistor T1 is an RF amplifier and C3 applies positive feedback to it. A simple regen receiver is overloaded by strong local stations and since it has poor selectivity then it will probably pickup a few strong stations at the same time. A...
  5. Audioguru

    Finding a good soldering iron....

    No. 60/40 solder is for plumbing and it remains pasty so it can be molded while it cools. I hate trying to connect electronic things with 60/40 solder because if the joint is moved a little while it is cooling then it forms a bad connection. 63/37 solder is eutectic for electronics and a good...
  6. Audioguru

    What battery do I need for these LED bulbs?

    The datasheet for an Energizer A23 alkaline battery shows that its duration is only a few minutes if you try to power 4 of those LEDs at the same time. Most of the battery power is heating the resistors attached to each one. You might even see the light slowly dimming. The A23 battery has eight...
  7. Audioguru

    Dynamic mic amp as clap switch

    Most little transistors need a base voltage more than 0.6V to properly turn on. They also need the voltage with enough current. Your schematic has no supply voltage shown so we cannot calculate how much base current a typical little transistor will need. How will you cut the clap sound short so...
  8. Audioguru

    Best way to reducing voltage

    A 3.8V Li-PO is 4.20V when fully charged and about 3.2V when it should be disconnected from its load, then its half-discharged voltage is 3.7V. If you discharge a lithium battery to 2.8V then it is damaged. If you use a simple voltage divider then you should calculate the minimum and maximum...
  9. Audioguru

    Question about a bluetooth headphone battery.

    The model airplane batteries do not have the circuit board with a charger and/or protection circuit on it and would probably blow up and catch on fire if you tried to charge the Bluetooth headphone with an airplane battery soldered onto it. The charger and protection circuit are in the airplane...
  10. Audioguru

    Dynamic mic amp as clap switch

    Any echo of a clap sound will cause a malfunction because the sound must completely stop before the relay contacts change connections. Every indoor room has an echo. 0.6V is too high at the output of the preamp for it to turn a transistor off. Make it 0.4V or less like for TTL logic. Then...
  11. Audioguru

    Trying to repair my power supply

    It is a polarized tantalum capacitor that explodes if it is connected backwards. It is printed 35k not 35V. I used tantalum capacitors 50 years ago and they all blew up but none were connected backwards. All had the manufacture's name on them and if yours does then you can look up what the...
  12. Audioguru

    Basic Audio Circuit Board Enquiry (novice)

    Female connectors like that are available in many sizes. There is enough wire length on your connector to solder on a new cable and cover the solder joints with shrink tubing. Buy a cable with two plugs like the one plug you need and cut off one plug. One wire is left channel, one wire is right...
  13. Audioguru

    Vacuum in a Can

    If you connect a vacuum cartridge to something that has normal gas or liquid pressure then the pressure in each would become the average.
  14. Audioguru

    Need Help In This Pcb Circuit

    The funniest little capacitors I have ever seen. Twins?? I am a twin and I don't look like that.
  15. Audioguru

    Solar Based Handheld Led Light

    Your circuit has almost nothing to control the battery charging current except R2. Di you calculate minimum and maximum charging current through R2? The solar panel will produce a very high output power when it directly faces the sun at noon in the middle of summer on a sunny day and produce...
  16. Audioguru

    Wireless ECG electrodes

    After a heart attack and my heart arteries being fixed, I wore a portable ECG a couple of times that recorded the ECG for 24 hours. I even wore a portable blood pressure cuff that woke me every hour while it did its thing. My hearing aids talk to each other and are programmed wirelessly with...
  17. Audioguru

    220v speaker problems

    Why can't you power it from the 240VAC used for your oven and clothes dryer?
  18. Audioguru

    Help me design a water heater circuit that automatically turns-off when the heater reaches a boiling

    My electric kettle has a fine screen that blocks steam at the spout and when the steam pressure is high enough it pushes the switch off. Then it is not affected by altitude. But it doesn't turn itself on again.
  19. Audioguru

    Need Help In This Pcb Circuit

    How can you make this project without a schematic, parts list, pcb design and parts layout diagram??
  20. Audioguru

    Low side switch

    A cool incandescent light bulb resistance is about 1/10th its hot resistance so it will probably burn out your Mosfets and power supply when you first turn it on. Using a toaster or a heater are a little better but their resistance also change with temperature. The output voltage from a micro...
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