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  1. Sunnysky

    Common collector configuraton

    Also if you know for a limited current range, in a low power diode Vf=0.65 +/-0.05 , and say a white LED is 3.2 is 5x this forward voltage , .... can you understand how it's % tolerance is 5x this amount? or +/- 0.25, this is a justification for the wide range in Vf in LED specs which is...
  2. Sunnysky

    Common collector configuraton

    if you drive Vb from 5V without current limiting to a emitter white LED, it may work in an emitter follower with a Series R but you are only using the transistor as a diode and all current goes thru base and none thru collector. bad practise.
  3. Sunnysky

    Common collector configuraton

    LED Vf is based on chemistry and power rating for Vf. Higher power have lower ESR. ESR has a wide tolerance depending on source quality. THere are no 5V LEDs but some lamps have a series R added. Red/Yellow 5 mm LED = 1.8 V + 15Ω * If. or Vf=2.1 nominal. (15Ω is estimated ESR in 5mm)...
  4. Sunnysky

    Amp In Protection Mode

    yes as I calculated only 50-100k leakage resistance with Vce~45V, this would appear as a slope on a beta curve tracer.
  5. Sunnysky

    That awful "yellow glue" - How to remove it?

    Since seeing the photos, there is no exposed copper , you can get away with any clear silicone sealant. So RTV is no longer necessary, just use that after testing no more arcs. Solder mask is an epoxy based insulator on bottom side but surface contaminants must be removed as much as possible.
  6. Sunnysky

    Amp In Protection Mode

    Q603 will pass diode test
  7. Sunnysky

    Amp In Protection Mode

    you might consider using Q603 from Good channel in bad channel,,restore all connections and try to null.
  8. Sunnysky

    2 transistor oscillator

    I would only expect a single tone. each transistor inverts the signal with gain so the capacitor feedback
  9. Sunnysky

    Led's headlight issue

    sorry. 20W
  10. Sunnysky

    Noise Activated Switch, with a Difference.

    I designed a tone pitch detection circuit 40yrs ago for quadrapalegics but it is a little complicated to build from scratch without skill as I used jumpers on board at the time for proof of concept. Whistle sequence activated switches. Then later at work in the early 80's everyone in an open...
  11. Sunnysky

    Led's headlight issue

    I used 10 Ohm or 1.4A roughly 82% power point. You can start anywhere like two halogens in series as half power to hunt for the threshold.
  12. Sunnysky

    Noise Activated Switch, with a Difference.

    A bandpass filter rejects unwanted signal best with a suitable duration to match the intended signals. Get a mic that won't rattle or pick up floor noise and measure on a PC With Audacity to capture the signal, then choose Tools> Analyze frequency and pick the range .. probably in the 1kHz...
  13. Sunnysky

    That awful "yellow glue" - How to remove it?

    I suggested only covering the cut areas. But if it works now , don't fix it until next time. Then cut more and coat cut spots with RTV
  14. Sunnysky

    RF question for multiple transceivers on one antenna

    ensure Tx is disabled before switch to Rx
  15. Sunnysky

    78L33 regulator

    If you test it with a relay power cycling every few seconds on / off for a few days with zero failures at highest ambient,then you can verify reliability.
  16. Sunnysky

    That awful "yellow glue" - How to remove it?

    GE made RTV is the non acidic or vinegar smelling silicone for electronics. not sure who sells it now. It survives extreme high temps and has long shelf life. It can be applied to denatured alcohol clean surfaces for best insulation. It also has a greater dielectric constant than air , so...
  17. Sunnysky

    Appropriate Oscillator

    What is this for? drive current and load type? It may affect the best choice of driver.
  18. Sunnysky

    78L33 regulator

    Using 4 diodes or a diode bridge allows less ripple and lower input voltage than 24Vac Normally one measures Vin dc and ac (p-p) or scopes Vin min to ensure dropout Voltage above Vout to regulator meets requirements. There are many other solutions to this problem. But if you are happy with...
  19. Sunnysky

    That awful "yellow glue" - How to remove it?

    Good work so far. My guess is this circuit is flyback transformer. to produce about 350V to supply the CFL backlight and that the yellow stuff was intended for the tall cap for support and not the transformer. I think widening the gap is OK to do since there are no tracks topside for future...
  20. Sunnysky

    Casio keyboard won't turn

    look for overheated parts inside
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