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  1. (*steve*)

    Transistor amplifier configuration for transmitter antenna

    The first step is to match the amplifier's impedance to that of the antenna.
  2. (*steve*)

    How To Prevent Short Circuit With A Simple Wire From One Outlet Prong To The Other

    An open circuit or half a brain.
  3. (*steve*)

    LED Wiring

    Not for LEDs without series resistors. Try connecting one up for an instant. If it's not greatly brighter than usual, connect it again and measure the voltage with it connected.
  4. (*steve*)

    LED Wiring

    Yes.
  5. (*steve*)

    Stage Line 500W amp repair project

    That's a damn shame. I hope there's someone in the UK who can take it over.
  6. (*steve*)

    Transistor pair to switch between Voltages

    AAAAGH "swapped". Bloody autocorrect. Yeah 10k for the LEDs is a bit high. The one on the 5V input need to be about 1/3 of the value of the one indicating 12V if you want equal brightness.
  7. (*steve*)

    Vacuum Tubes

    Had there been active development I'm sure this would have reduced. Some 1950's era valves had heaters which consumed in the low tens of mW. I wonder if there was ever research on "room temperature thermionic emitters"? However I can't imagine an integrated tube with a billion devices in a...
  8. (*steve*)

    Could you guys help identify some things?

    Looks like an electrophoresis power supply and another short wave radio.
  9. (*steve*)

    Could you guys help identify some things?

    Not sure what it is, but if you find a knob with a clear disk attached to it and having some sort of dial markings on it... It might belong to this.
  10. (*steve*)

    Could you guys help identify some things?

    A short wave radio.
  11. (*steve*)

    Could you guys help identify some things?

    That is just so cool. Would you send it to Australia? :-D
  12. (*steve*)

    Could you guys help identify some things?

    Those appear to be radio shack brands. Probably not going to be worth much. The bottom one is for tweaking video signals. It may be of use to someone who is trying to capture old VHS tapes. Not sure what the top one is. If RS stands for something other than radio shack it would be a good...
  13. (*steve*)

    Could you guys help identify some things?

    That is a microphone mixer. Shure is a good brand and someone might pay money for it. Find some musicians :) You should be able to upload multiple pictures per post but if you keep uploading one at a time it's probably easier for us to reply about them.
  14. (*steve*)

    Keithley 600B input mosfets

    AAAAGH! RTFM I have been reading the calibration instructions wrong. Of course the reading will wander all over the place when set for voltage measurements with the input open! The input leakage measurements are done in the amps mode. As near as I can measure, the leakage is a measly 5 x...
  15. (*steve*)

    Wayne Kerr 7010 manual

    That's amazing! Thanks.
  16. (*steve*)

    Transistor pair to switch between Voltages

    All good except you have drain and source sealed on your MOSFETs. The LEDs will probably be very dim.
  17. (*steve*)

    Battery charged by a solar panel?

    As per @Audioguru, the max current from the panel must not be too high for the battery. For lithium cells, a simple shunt regulator can be used to limit the cell voltage. See this thread for the design I've used. You will have to recalculate the voltage divider to get a voltage of about...
  18. (*steve*)

    Keithley 600B input mosfets

    I fitted the batteries into the other 600B and it has exactly the same drift issue. I guess there are a few possibilities: This is correct behaviour It is caused by the slight difference between the murcury cell reference voltage and my replacement Both units have the same fault in the input...
  19. (*steve*)

    LED Circuit Help.

    A small 9V battery probably won't last very long. Go to the resource section and read the resource on driving LEDs. It has pointers to several LED calculators which will help you in your calculations. You will be best off using one resistor per 3 LEDs.
  20. (*steve*)

    Help.. Modifying a circuit to eliminate 30 minute time out

    Perhaps the easiest answer is to use a magnetic reed switch (like the window alarm switches) to detect that the door is closed. If it's not closed it must be open!
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