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  1. Externet

    i need to find those variable capacitor

    Pick your flavor ----> https://www.aliexpress.com/wholesale?SearchText=variable+capacitor&opensearch=true
  2. Externet

    Led from Mercedes headlight

    Get the vehicle wiring diagram to check if there is a power module driving the LED. That power module will be mandatory to use and fed by the 12V battery.
  3. Externet

    Retail product that can supply 120V/30A from battery?

    As BobK says, you are aiming to a plain wall outlet; aim instead to a dedicated connection to a 30A circuit breaker from the mains circuit panel.
  4. Externet

    Capacitor terminals

    Apply 12V or near to that, any polarity to the terminals for a couple of seconds. Measure voltage at the terminals with your multimeter after say 10 minutes. If healthy, there will be a voltage reading. The closer to 12V, the better. If no voltage, it is bad.
  5. Externet

    Laser diode power questions

    If the laser pointer was meant to be used only with a fixed voltage as "5V", a resistor would suffice and the chinese would not spend half a penny extra in its manufacture implementing circuitry. But the driver circuit implies the constant current is produced from the components, so it should...
  6. Externet

    Laser diode power questions

    The one on the Ebay link is a module containing a laser diode and driver circuitry. It regulates the laser current for variations in supply voltage. How big can the variations be is in the always absent chinese data sheets, but perhaps can be found for similar modules/schematics.
  7. Externet

    Gain of operational amplifier...

    Thanks, gentlemen. That fuzzy schematic does use a AD8628. Other similar circuits with the sense coil and other instrumentation amplifier ICs show the coil directly to inputs, but have provisions for gain setting. The intention is attempting to detect a 1Tesla magnet slowly spinning at less...
  8. Externet

    Gain of operational amplifier...

    Hi. Is the gain in this case, Rf/Ri = R1/R2 = 10K/100 = 100. Is that correct ? The coil itself has 1000Ω DC resistance. Is the gain still 100 or is it Rf/Ri = 10K/ 1100 = 9 ? If R2 is substituted by 0Ω, the coil being 1KΩ. What is the gain ? The point is if the coil can be considered as a {0Ω...
  9. Externet

    Component Identification

    A flickering neon bulb tells it is tired. Try replacing the bulb instead of the series component. On the subject, a small value capacitor in series would be also a current limiter for a neon, but I have never seen such configuration used. Have you ?
  10. Externet

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

    Disconnect the higher heating element, fill it to half, and set the thermostat to 180F. It will take 230V AC ----> http://www.sears.com/kenmore-55-gal-tall-12-year-electric-water/p-04232154000P
  11. Externet

    Vintage Hardware, should we begin replacing TANTALUMs

    From own experience, my two different model audio analyzers -same brand, same age- one had periodic failures of tantalums. Perhaps six times = six troubleshooting events to fix. The other has not failed. I suggest modify/improve power supplies to ensure no spikes can take place instead of...
  12. Externet

    Need to replace odd value capacitor

    Hope cleaning/scraping/fixing that works. You will need to work under a microscope and with very skilled hands. If not successful , whatever connects to those traces may be affected. And observe carefully, that several traces are the same connection.
  13. Externet

    Need to replace odd value capacitor

    Yes, a DC power adapter-supply applied for a few seconds with proper polarity to the capacitor can tell if it holds charge. If without desoldering, it will be affected by any internal circuitry. If there is a problem inside, it may not show as holding charge.
  14. Externet

    Need to replace odd value capacitor

    Look for a typical xenon flash circuit if you have no schematic to evaluate what could have suffered from the short circuit. If the capacitor shows no voltage now, with the flash enable ON, the DC to DC converter circuit is troubled. Desoldering the capacitor and applying -say 12V- or more to it...
  15. Externet

    Need to replace odd value capacitor

    Likely did not damage the capacitor but if the screwdriver was touching something else than the capacitor leads, then you are in trouble.
  16. Externet

    Need to replace odd value capacitor

    That 'nasty spark' showed the capacitor was good, holding charge; and delivered a lot of energy into somewhere, frying something else. that capacitor is to be discharged with a resistor across for a while until reads 0Volts. You may have something else badly vaporized in the circuitry.
  17. Externet

    Need to replace odd value capacitor

    It is a very common value, obtainable from a disposable film camera. Will have to dismantle a few to pick the correct dimension. I have about 2 dozen different... if you specify the size. And a variation in capacity should not matter much. Should be for the flash circuitry. How did you...
  18. Externet

    Series bulbs with rectified AC

    I would say the filaments would run cooler and the 'vibration' would be half the amplitude, with at least 5 times life. I use backyard incandescent 230V-200W bulbs fed by 120V instead of 120V-75W bulbs and so far, 10 years with no replacements. Did the same for a 120ft tall antenna tower red...
  19. Externet

    Electricity Consumption for Ceiling Fan?

    A ceiling fan is not the way to cool a kitchen from its stove sweaty heat. That would only spread heat, fumes, and grease. That job is for a vented hood fan. Which is not the same as a grease collecting recirculating fan hood as : ---->...
  20. Externet

    What polarity is this?

    Do not see that as a polarity indication, that symbol clearly tells me the RCA jack is 'audio out'
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