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  1. smokyLED

    unkown ic

    I'm trying to find a replacement for an IC in my frequency counter. It's a 8 pin DIP, and could possible be a opamp. But i'm not sure. I have googled but haven't had any luck. This is with is printed on the package: TFK 731 666 BS TFK666BS seems to be the product code. Thanks in advance.
  2. smokyLED

    Goodwill gfc-8100g frequency counter

    anyone have a user/service manual for this? my channel b shows random values even when there is no input.
  3. smokyLED

    heating ammonium/sodium persulphate

    what is the best way to heat up used ammonium persulphate? i store it inside a plastic bottle after using it, and i don't want to put it in the microwave.
  4. smokyLED

    0-24V 4A bench supply

    I have built this circuit, and i can adjust the voltage and current correctly using the pots. However the current limiting and temperature cutout doesn't seem to work. I am getting no voltage at pins 7 or 8 of the LM324. PARTS TF1 230/24V 100VA transformer F1 1A fuse F2 6A fuse SW1 on-off...
  5. smokyLED

    LM317K regulator current problem

    I'm making a bench supply out of the 5A Constant voltage/current circuit on page 16 of the LM317 datasheet http://cache.national.com/ds/LM/LM117.pdf. I've replaced the MJ4502 transistor with a MJ2955 TO-3 transistor. Thing thing works fine for current up to 1A, adjusted via the pot. But once u...
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