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  1. BobK

    need help to find alternative IC

    If you could find one, it would probably cost more than replacing the entire charger. Bob
  2. BobK

    Need A Lot Of Help

    R4 is definitely good. R3 is probably good, the incorrect readings are due to the rest of the circuit. Bob
  3. BobK

    Need A Lot Of Help

    The 2K range is the wrong range to read 100K and 1M. Try the 200K and 2M ranges. What Steve was asking for was to show what the meter reads with the probes shorted together and the probes connected to nothing. This would tell us what an out of range indicator looks like on your meter. Bob
  4. BobK

    Switched power supplies - 0V with load.

    Unless ot is put in parallel.
  5. BobK

    Broken LCD display on Makita 104 Radio

    That looks like a fairly standard 2 line bt 20 character LCD. If you could take it out and show more pictures we might be able to find a replacement. Bob
  6. BobK

    Pioneer SX 850 Receiver

    Something is wrong you measure 18V on the good channel. It should measure near 0V, which you say you get on the good channel. Bob
  7. BobK

    Trying to understand PWM / solve relay buzz

    That is an interesting idea, but it would essentially be a buck converter, reducing the voltage based on the duty cycle of the PWM signal. Bob
  8. BobK

    digital timer that can be set to a minimum of six different times

    T Try 3 days, to me, the software is the easy part :) Having just gone though several years of dealing with my elderly father-in-law, now deceased, I was tempted to develop something like this. But my plan was even more ambitious. I would have had it play recorded messages for each alarm to...
  9. BobK

    Trying to understand PWM / solve relay buzz

    Indeed! I must have stolen that from somewhere. The capacitor, in this usage, is analogpus to a battery that charges when the signal is high and dischages when it is low. The current does not go in one terminal of a battery and come out the other one. The circuit will work just fine with a...
  10. BobK

    Trying to understand PWM / solve relay buzz

    The reason it works is that the capacitor charges while the PWM signal is high, then continues to supply current to the relay when it is low. The diode prevents the current from flowing backwards from the cap to the source of the PWM signal. I don’t recognize that schematic though Bob
  11. BobK

    Sherwood Power Amp Crossover Distortion

    Now the curcuit with a single diode makes sense. One diode drop will have both MOSFETs on. You need seven volts for your replacements. I would look for something else at this point. Bob
  12. BobK

    powering 36 DSLR cameras from a single powersupply

    Measuring the current might be tricky. The camera likely draws a burst of current when you take a shot. If all 36 are triggered at the same time, you have to allow for that max current. You might not be able to read it with the multimeter. A storage scope would be better, but I doubt you...
  13. BobK

    Harman/Kardon HK6500 restoration - need advice

    Sounds like you are doing the right stuff. The filter capacitor is not critical, I wouldn't bother paralleling two. If you can fit it, a slightly higher value would be better than a lower one. 15000 uF? Bob
  14. BobK

    pic16f88 sleep and wake on interrupt

    Don't know the details of MicroC, I use Microchip tools, but it should be pretty simple. You need to enable the specific interrupt and enable all interrupts by turning on GIO. Then you sleep. The interrupt will awaken the processor. You need an interrupt handler, but it does not have to do...
  15. BobK

    ridiculous harvest

    When I was 5 years old, my family stopped in Hawaii on the way back from Okinawa where my father had been stationed. Apparently the only thing I was interested in seeing was where the pineapples grow, and the driver who was taking us on a tour accommodated me. Bob
  16. BobK

    Sherwood Power Amp Crossover Distortion

    I think it would be in the range of a few hundred ohms, but this is only a guess. Have you compared the gate threshold voltage of the original MOSFETs as opposed to the new ones you installed? If my theory is correct, the new ones should have a higher threshold. Bob
  17. BobK

    Sherwood Power Amp Crossover Distortion

    With BJTs 1 diode per transistor gives you about the right drop (2 for single output transistors, 4 for darlingtons). With MOSFETs it is anybody's guess how much voltage you need between the two gates. Most MOFSET output stages I have seen incorporate a pot to adjust that voltage, since the...
  18. BobK

    powering 36 DSLR cameras from a single powersupply

    Do you have a multimeter? It does not use 2A or the battery would last about 20 minutes at most. Bob
  19. BobK

    powering 36 DSLR cameras from a single powersupply

    Easy. Multiply what one camera needs by 36. The current that is, the voltage stays the same. Bob
  20. BobK

    Direct connecting solar panel to 18650 lithium cell...

    You always need a diode, or the battery will discharge through the panel when it is dark. Bob
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