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  1. AnalogKid

    Stereo audio mixer build

    You cannot run audio through a diode (and have it remain audio). Why do you think you can? ak
  2. AnalogKid

    Stereo audio mixer build

    All three active mixer schematics have the same problem with the output. Placing a 10K pot between the opamp output and the connectors means that the output impedance varies between 100 and 5100 ohms as the pot is rotated. Not good. Better to put the pot between the first and 2nd stages...
  3. AnalogKid

    Power supply !!

    It does look like the diode is in backwards, but that is a strange schematic, and the 1N649 is a very old part. It looks like the bulk filter capacitor is *after* the regulator. Also, the feedback point is before the output current meter shunt, which decreases the circuit regulation. From 0...
  4. AnalogKid

    STOP 2nd phone line from ringing

    Do you know what the ring voltage frequency is? With the right relay, this can be done with zero active components: Capacitor Diode bridge Filter capacitor Relay coil ak
  5. AnalogKid

    Darlington transistor hfe.

    The recommendation to use an NPN transistor came before you decided to share your schematic. Now that I wee that you meant *current* boost, not voltage boost, stick with PNP transistors. They are the standard part for your circuit. Suggestion: add reference designators to all components; int...
  6. AnalogKid

    I need to maintain a half-full 55-gallon drum at 180°F?

    Fill with what? Dishwasher heating elements are designed to run straight off of a country's AC grid, so 120 Vac in the US. How tight does the temperature control have to be? Omega Engineering and other industrial supply companies have lots of thermostats with sensors. ak
  7. AnalogKid

    Frequency counter

    Depends on the construction. The pass transistor is a 2SD146, which is a 40 V, 1 A part. It crosses to a 2N4912, which is an 80 V, 1 A, TO-66 part, so it doesn't have a huge radiating surface. Using the regulator output will make for less hum, but more heat. My guess is that it more than...
  8. AnalogKid

    Frequency counter

    If you have the correct manual with the schematic, please post it. Based on the DX-150 manual - The additional 160 mA load is increasing ripple out of the power supply bulk filter capacitor to the point that it is getting into the audio power amplifier at an audible level. There are no...
  9. AnalogKid

    Get your tin foil hats out....

    They?
  10. AnalogKid

    Frequency counter

    You have given so little information that it is impossible to say. Could be that the secret frequency counter secret power requirements are greater than the secret receiver can provide. Do you know any of the voltages or currents? ak
  11. AnalogKid

    Hello can somebody tell me, how come 10mA this current source

    Note that the schematic in post #1 has a problem. The high impedance and high compliance 10 mA output point is not the emitter of Q7. It is between the collector of Q7 and ground. If you want the 10 mA to go off and do something like light an LED, that is where to connect it. ak
  12. AnalogKid

    STOP 2nd phone line from ringing

    When a phone is on hook voltage is 48 V, continuously. The 90 Vrms ring tone is superimposed on this. The 48 V is not a hard-regulated power supply output, but a 48 V source through an impedance such as 900 ohms. When a phone goes off hook, it loads this soft voltage source and pulls the line...
  13. AnalogKid

    STOP 2nd phone line from ringing

    Completely eliminating the ring signal would be difficult. What you can do is detect a certain voltage level that reliably reflects the start of ringing, and use that detection to disconnect the downstream phones for 1-2 seconds. If you answer the phone in the middle of a ring, you would not...
  14. AnalogKid

    STOP 2nd phone line from ringing

    If there is no ring signal, but only a ring code (a pretty important detail to leave out), then the only way to stop ringing is to examine the code as it goes by, looking for the ring code, and setting the ring code to non-ring before passing it on to the phones. ak
  15. AnalogKid

    Radio Silence

    If it looks like a greenish or redish varnish, that is glyptol or loc-tite. Usually if you get a screw driver that fits the head *perfectly*, you can press down and turn the screw and break loose the adhesive. Photos? ak
  16. AnalogKid

    STOP 2nd phone line from ringing

    If the phone has a ringer that is separate from the receiver (speaker), then disconnecting the ring device will stop all ringing without affecting any other functions in that or other phones. ak
  17. AnalogKid

    Unable to read frequency of a tone signal with a frequency meter.

    Where is this schematic from? Do you have a schematic that shows the individual gates as components so the drawing conveys some kind of information about the circuit? Also, why are pins 12 and 13 brought out of the device as a single pin? Pin 11 is a NOR gate output. The signal there...
  18. AnalogKid

    Need to replace odd value capacitor

    Is this a motor start capacitor? ak
  19. AnalogKid

    Capacitor help

    That capacitor type doesn't look particularly new to me. If you have a clear idea of its use, application, applied voltage, etc. there probably is a more reliable part to use. ak
  20. AnalogKid

    Capacitor help

    Interesting assembly. What is it? ak
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