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  1. KJ6EAD

    Vintage stereo receiver re-lamp with LEDs

    How do you know the dial is AC? It doesn't matter which lead you put a limiting resistor on. Yes. The flat tops will have a wide dispersion so that's good. Since you're getting enough transmission of the color you want through the filter, you don't have to use blue LEDs in this case but it's...
  2. KJ6EAD

    Vintage stereo receiver re-lamp with LEDs

    Measure the actual voltage being supplied to the lamps and determine whether it's AC or DC first and whether it's stable or varying. The voltage for dial illumination is probably fixed but the voltage for the stereo indicator is another matter. Doing the math based on the lamp rated voltage is a...
  3. KJ6EAD

    Electret Microphone - Activate LED's

    If you Google "sound to light" or "color organ" you'll start to find some circuit designs and kits that do most of what you want.
  4. KJ6EAD

    New Member

    Welcome to the forum Bob. You're lucky; the Electronic Goldmine is in Scottsdale. http://www.goldmine-elec.com/
  5. KJ6EAD

    Battery comparison for emergency light

    SLA (sealed lead acid) will be more economical than any of the battery technologies in your list, but it's not in your list. Why not?
  6. KJ6EAD

    Monsoon MH-500 Speakers - Need to know what IC is in U5 on board

    90N909 is a production or date code. The part will be much easier to find if you look for it by it's part number, TL082CN. Of course, that's not the one you need.
  7. KJ6EAD

    CRT TV No vertical deflection after changing vertical ic and capacitors around it.

    I circled the rest of the potential problems. The large resistor and the transistors would be my first choice of components to check or replace, followed by the diodes, the remaining electrolytic capacitor and then the polypropylene film capacitors.
  8. KJ6EAD

    Hissing in ATX power supply.

    Transformer windings vibrate and insulation wears through. They also experience thermal expansion and contraction in use which causes annular cracks in winding insulation, especially after high temperatures have embrittled the insulation. It doesn't address the transformer matter but the white...
  9. KJ6EAD

    Resistor reading on Multimeter help!

    That resistor has a lot of oxidation on the leads. Make sure your meter is making contact with clean metal.
  10. KJ6EAD

    Electronic whack-a-mole

    Not to spoil your fun, but Bob's Space Racers licensed the Whac-a-Mole game to Hasbro to make a small electronic version. It's been on ebay for $10.
  11. KJ6EAD

    Help me diagnose circuit problem

    Check the fuse.
  12. KJ6EAD

    Including my PayPal information in my profile

    That's well stated and a philosophy that's consistent with the forum's ideals. That's a good point but the forum owner(s) will likely want to prevent the forum from becoming an engineering/technical services bazaar, however well-intended. I think this is the slippery slope that Dave warned of. I...
  13. KJ6EAD

    Including my PayPal information in my profile

    There should be a tip jar attached to each member account. :D Maybe requesting that people PM you for the PayPal info would appear less commercial.
  14. KJ6EAD

    Can I Reverse DC Plug polarity

    If it's a molded cable/connector it's best to change the polarity at the source end inside the PSU if it can be opened. Look for screws hidden under rubber plug feet, etc.
  15. KJ6EAD

    Led sequencer/scanner

    That's what I was thinking too but you can eliminate 18 of the LED current limiting/splitting resistors by creating dual resistor limited ground rails using just 2 resistors. This is possible since only one 4017 output channel is on at a time.
  16. KJ6EAD

    Current Limiting and Heat

    Did you compare the operating current of the two setups?
  17. KJ6EAD

    Current Limiting and Heat

    Following Kris' percentage rule of thumb, which is a good rule though I sometimes go to 10% when using a well-regulated switch mode power supply, as the length of the series string increases, the voltage drop and consequently the wattage dissipated in the resistor also increases. This is why for...
  18. KJ6EAD

    Led sequencer/scanner

    First, you need a base resistor (~2.2k) for each of the transistors. There's no problem with a 12V battery supply. I mentioned the use of an LM317 as a current sink, not as a voltage regulator. If you don't use it, you have enough voltage to drive 4 LEDs in series with each transistor but...
  19. KJ6EAD

    Led sequencer/scanner

    It depends on what you consider too much. If you only wanted to sequence in one direction, from ends to center, you would only need one 4017. No, the 4017 can only drive ~15mA so you would need a driver transistor on each output group (2 or 4 LEDs). I might use a transistor array such as a...
  20. KJ6EAD

    Lemon organic batteries 0.6Volts per lemon

    The other factors that will affect the performance of your chemical cells are electrode material, electrode surface area and distance between electrodes.
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