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Recent content by GCook

  1. G

    Home Smoke detectors are all Beeping Batteries are not dead.???

    The house AC wiring being common to all of them, would make me check the AC voltage going to the detectors. If they are all on the same circuit breaker, AC voltage is even more suspect. If they are all on separate circuits, check the mains coming into the house. A problem with the power...
  2. G

    Lightbox circuit

    On the main board schematic there is a J2 input connector with two terminals (SIGL and GND). Connect there.
  3. G

    Lightbox circuit

    The main board. Not the input board.
  4. G

    Lightbox circuit

    Connect one end of a alligator clip jumper to SIG. Connect the other end of the jumper to a 1/4 watt, 50K resistor. Connect the other end of the resistor to a second alligator clip jumper that you will attach to GND.
  5. G

    Lightbox circuit

    If you have a 1/4 watt, 50K resistor, just jump the SIG input to GND. The successful result will be that the resistor remains cold to the touch, and the noise goes away.
  6. G

    Lightbox circuit

    Nigel- I'll be quiet, and just sit back and watch. Splitdog- Your meter says it's not, so I guess it isn't.
  7. G

    Lightbox circuit

    Okay, I see it on the other schematic. I guess you figured out I was just focusing on the input board. I'd like to know why the circuit needs it. I'd say (after looking at the main input circuitry), that C20 is used to block the DC voltage. I still believe the pot on the input board needs a GND...
  8. G

    Lightbox circuit

    Does one of the outer pins of the pot connect to GND? You'll have to look at the trace side of the input board.
  9. G

    Lightbox circuit

    The 33K resistors are probably to keep the input from being over-driven (distorted). I don't see the DC voltages that Nigel is talking about. I only see three possibilities of AC at the input. The SIG input appears to be just hanging out there like an antenna, with no reference to ground. That's...
  10. G

    Lightbox circuit

    You're getting noise, because it's acting like a radio receiver antenna. Without the input pulled down, it is extremely sensitive. It needs a proper input to silence it. Try placing a 50K resistor or something close to that size (with no other connections), directly across SIG and GND, and all...
  11. G

    Lightbox circuit

    The more I look at it, that's not going to be the answer. Without an additional resistor between the pot and GND, the line-level or speaker-level inputs would go straight to ground when attenuated completely. I'm thinking that a resistor is missing, that should be connected between GND and the...
  12. G

    Lightbox circuit

    The drawing doesn't show the pot connected to GND. The pot may need to be across SIG and GND, allowing the signal to take alternate paths to GND or the input slider tap of the pot (to R1).
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