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  1. duke37

    Old "Kay" guitar amp question

    The current consumption seems to be excessive even on your low voltage:).(100W?). What is getting very hot? I have no data on the 6N6 so it could be a rare valve. The 6L6 is running in class A and its current should not change with signal level unless you are running into distortion. The bias...
  2. duke37

    Philco Radio Parts Identification

    The voltage drop across the speaker is about 85V so about 80mA. Power is I*I*R so the 150Ω resistor (#60) will dissipate about 1W. Use a 2W resistor if you have to replace it
  3. duke37

    Microphone for low frequency recording use

    Earthquake detectors have to respond to very low amplitude and frequencies. These are done by measuring the distance on a freely suspended weight from the earth. Use LVDT or capacitance?
  4. duke37

    Philco Radio Parts Identification

    The parts are resistors 59 and 60. The big one is body tip dot but the body and tip are the same so it is not obvious. 150Ω
  5. duke37

    Philco Radio Parts Identification

    The resistors could be body, tip dot. I cannot see the dot on the big one but the other could be 15Ω. Measure the valve voltages and see how they compare with normal levels. If the schematic is the one you want, it should give voltages.
  6. duke37

    I buy am/fm radio kit but something i dont understand

    I have used 5spice to plot the effect of the feedback capacitor across Q2. Both transistors were simulated as 2N2222. The red line is 100pF The top black line is 1000pF. 470pF will come between these two. The 800μH inductor affects the response at frequencies well above audio. The advantage of a...
  7. duke37

    These transistors needed

    Check the connections.
  8. duke37

    Have seen many Youtube videos related to induction heaters but never for water?

    Where do you find a heat pump the can deliver more than 50C? I considered a ground source heat pump to heat my house using a stream at 10C. The coefficient of performance was rubbish above 50C and the installation cost was astronomic.
  9. duke37

    Non-inverting audio Op-Amp

    It is still not clear what you want to do. What is the signal level of the source and its impedance? What is the required level of signal and the impedance of the load? You want a non-inverting amplifier, why is this? An inverting amplifier can give amplification and attenuation.
  10. duke37

    Help required with identifying a component

    Have you tested the diodes? It looks as if you have plenty of room to fit diodes with leads,. 1N4004 to 1N4007.As cheap as chips:)
  11. duke37

    I buy am/fm radio kit but something i dont understand

    I was thinking along the lines of what gain the transistor should have. With 5V on the collector (halfway approx) there is 4V across the 2k2 resistor so the collector current will be 1.82mA. With 5-0.7V across the 1M resistor, the current will be 4.3μA The gain of the transistor (beta) to get...
  12. duke37

    I buy am/fm radio kit but something i dont understand

    800μH An inductor will have an impedance of 2*pi*f*L, it needs to stop high RF frequencies and pass audio frequencies without too much attenuation. You could assume the input impedance of the following transistor is about 1kΩ. Calculating the frequency at 1kΩ. f=1k/(2*pi*L) = 200kHz so it will...
  13. duke37

    I buy am/fm radio kit but something i dont understand

    The μ symbol is available up top. The inductor and capacitor needed will depend on the transistor characteristics. To see the effects, you could do a simulation using LTspice. You want a response up to 5kHz or so. In #2 I said that the transistor was a common base, it is of course a common...
  14. duke37

    I buy am/fm radio kit but something i dont understand

    I do nor know what the input stage does, the 1N60 diode does not have a current source. The 2k2 resistor and the 1M resistor sets the current through the 2N3904 which is a grounded base amplifier. The 800μH (not UM) inductor reduces the RF going through to the final stage. The 1μF capacitor...
  15. duke37

    12 MHz oscillator with a Voltage range 120V

    Your english is quite good but you will need to give much more information. A range of 120V could be 100V to 220V. 120V power input? 120V output? power? load? frequency accuracy? waveform?
  16. duke37

    Help

    I wonder whether a rectifier is needed. I would try an electric welder which has a reasonably high voltage and will be designed to withstand a short. A simple AC one may do.
  17. duke37

    Trans former rewind

    The primary is the pink winding where the gap is. I would not under any circumstances put a winding on top of this for safety reasons You can of course take turns off the secondary as Minder recommends without dismantling Edit: The primary should not be modified in any way.
  18. duke37

    Trans former rewind

    Post a picture of the transformer, a torroid is more difficult to rewind. You will not need thicker wire if the original current capability is 500mA. You could take off an estimated half of the turns and measure the resulting voltage, then remove more to get the final value. You then do not need...
  19. duke37

    Non-inverting audio Op-Amp

    The circuit you show will always give gain. If you wish to reduce the signal level, get rid of the op-amp and use a potential divider. If I remember correctly, 20dB is a factor of 100 in voltage.
  20. duke37

    AM demodulation and DC offset

    You have the right idea but the time constant RC of your circuit is 1ms. The Mullard manual of transistor circuits uses 0.01μF and 5k giving a time constant of 50μs.if my sums are right. I think the resistor is far too high. A semiconductor diode would be better driving a lower resistance.
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