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  1. duke37

    Is it normal for an opamp to "rectify" a signal?

    The output socket is connected to -V. The output cannot go below this. Th socket should be connected to the centre ground of the power supply.
  2. duke37

    Need help with a PSU schematic

    Looks OK to me but you may like to put a double gap on the bottom track.
  3. duke37

    Too much battery

    The device will take only the current that it needs as long as the supply is 12V. It doesn't matter where it comes from. My guess is that you connected it the wrong way round, that is a sure way to disaster.
  4. duke37

    DIY 5X low wattage amplifier for Biotech research

    The voltages, currents and impedance do not match. 10V into 50R is 200mA. 3.3MHz seems to be transmogrified into 3.3mHz. A wideband amplifier should be possible.
  5. duke37

    Need help with a PSU schematic

    No ! The regulators will keep the voltage near enough constant reguardless of load. They will give low voltage if they overheat, have low input voltage or are asked for excessive current. Trimmers have a contact which may be poor, I never trust them. What would happen if they became open...
  6. duke37

    Tinning??

    I bought a pot of LA-CO regular soldering flux paste at a radio rally. It seems to work very well but the ingredients would appear to be corrosive. I emailed the makers to see if it would be suitable for electronic work but they have not condescended to reply. I think this should be...
  7. duke37

    Need help with a PSU schematic

    It is not whether ripple is good or bad, it is whether it is acceptable. The voltage at the bottom of the trough must be above that which the regulators need to work properly. Do not take the values shown in the graphs as accurate, there are many variables which I guessed at or neglected. The...
  8. duke37

    Need help with a PSU schematic

    And here it is fullwave.
  9. duke37

    Need help with a PSU schematic

    Rectifier + doubler (Tripler) I am no expert on LTspice. I modified a circuit which was a power supply for a valve radio and this is the result. I have simulated the early part of the circuit using half wave only. It could be extended by adding another similar circuit, running in antiphase...
  10. duke37

    are Triac's RF sensative ?

    I do not see why it is either or. Run the transmitter from another power supply and put a dummy load on the troublesome one. Get it immune to RF. Put a crowbar inside it with very little slugging capacitance so that it is quick. A fat SCR which will blow the fuse before expiring will be...
  11. duke37

    IGBT on resistance - conduction loss

    PWM seems to be well over the top for a heater. You could use phase angle control or a solid state relay switched by a timer circuit.
  12. duke37

    Newbie power questions

    You can get buck convertors which can take a high voltage and convert it to a lower voltage with higher current. The efficiency is about 80%. I have never used or made one.
  13. duke37

    AC Adaptor replacement for AA Batteries.

    They will be sitty talkies ! If you are fussy, you can put a silicon diode in series with the supply. This will drop 0.6V or so thus a 5V supply will give 4.4V. The diode also has the advantage that it will protect against reverse voltage.
  14. duke37

    are Triac's RF sensative ?

    You could put the crowbar in the power supply, this how it is normally done. This will have less RF pick-up. You could work out the schematic, it is hardly likely to be complicated if home built. A simple analog meter would be better in strong RF fields.
  15. duke37

    IGBT on resistance - conduction loss

    What is wrong with calculating? Mosfet P = 20 8* 20 * 0.075 = 30 IGBT P = I * Vce = 20 * 2.5 = 50
  16. duke37

    Lead-Acid BATTERY-Negative tab rotten& Chapped. Whyy ???

    To change from sulphate it is necessay that it is immersed in the electrolyte. I cannot help more in this topic but there was a good reference included previously giving details of the best way of preserving a lesd/acid battery.
  17. duke37

    are Triac's RF sensative ?

    So it is a home made supply, is it in a grounded metal case and does it have RF bypass capacitors with short leads on both input and output? Do you have bypass capacitors at input and output of any regulators? Is the circuitry built with short connections? Show us a the schematic and...
  18. duke37

    Need help with a PSU schematic

    The original circuit uses a 20-0-20V transformer, this will produce +28v and -28V after rectification with no load. A voltage doubler will give 56V and if this is stood on top of the +28V the result is 84V, all from a 20-0-20V transformer. Quite neat. The 47uF capacitors will have a fairly...
  19. duke37

    are Triac's RF sensative ?

    If the power supply is upset by RF getting into it, the obvious way is to stop the RF being sprayed around. The transmitter must be screened properly and fed either into a remote antenna or a properly matched, screened dummy load. Any electronic circuit will repond to an RF signal, it just...
  20. duke37

    Need help with a PSU schematic

    Dave Wikipedia describes the voltage doubler as a Greinacher circuit. I do not see how to down load the diagram, I could sketch and scan if wanted. The doubler as normally used contains two rectifiers. Here, two voltage doublers driven in anti-phase are used with outputs connected in...
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