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  1. dorke

    Faulty 9VDC Power Supplies

    You have a bulged capacitor (C6). That would be a typical fault of a SMPS like this one. Replace it.
  2. dorke

    Legality of non-amateur band receivers

    It is legal to listen to commercial(non-amateur) public radio/television bands. I believe it is illegal to listen to private conversations in most places for keeping privacy,that includes phone/cell etc. For the same reason it would be illegal to listen to non-public bands. Now days it is...
  3. dorke

    Mysterious vacuum tube

    It has 4 pins, 2 thicker (any side bayonet pin ?). Better quality pictures from all sides may help. The socket is called UX4( U4A).
  4. dorke

    Help with HD PCB part

    Your last chance,in case nothing else helps, is getting the disk to "a data retrieving company", they can retrieve the data(most of it) from a bad hard disk(scratched etc.) by reading it from the physical disk itself. The problem is this procedure is very costly.:(
  5. dorke

    Help with HD PCB part

    Part identified as 1SMA5.0A Onsemi 400W 5V TVS, part marking is QE. Available at Digikey from several sources,here from Littlefuse. If you are lucky,then this is the only part defective on the board.
  6. dorke

    Frequency and time confusion

    Let me add, All Signals may be represented in the time domain or frequency domain. They are like two sides of the same coin. The ability to "view" them in each domain is "handy", you should pick the one that is the simplest to handle/most useful/best to gain insight etc. Note that most...
  7. dorke

    Questions about Using LM358

    Well, First thing, it is better if you let us know what you need to accomplish in terms of input to output relations. What is the resistance of your current source? 1. The output of your circuit is indeed a simple V = IR relation(inverting), why did you expect anything else? 2. The LM358 is...
  8. dorke

    Generator question

    Changing the speed of the boat motor driving the generator will have 2 effects. Assuming there is no "control mechanism" : 1.It will change the output voltage,the faster the speed the higher the voltage. 2.It will change the frequency of the output,the faster the speed the higher the frequency...
  9. dorke

    Help in deciding method for de-modulating? a signal to extract one frequency!

    Benny, Are you trying to reinvent the wheel(Helm) here?;) There so many commercial remote controllers available...
  10. dorke

    Digi pot for pwm board

    Well not quit, from the graph a 50k pot would give you about 20KHz-500khz,blue on the graph. (notice the discrepancy as the max. should be 400kHz) . Using a 6.8nF and 50K pot will give you about 4KHz-100Khz,pink on the graph. Is this o.k for your needs? You should also note that digipots have...
  11. dorke

    Digi pot for pwm board

    About the SG3525A datasheet ,the product ,and your needs: First thing is to look at how is the frequency set with the SG3525A. It is given by the manufacture: That is a fairly simple formula,in which: CT= timing capacitor. RT=timing Resistor. RD=Dead_time resistor. second thing is to look at...
  12. dorke

    Digi pot for pwm board

    Can you define "Rapidly"? i.e what is the range of frequencies you need? larger values of the pot equate to "very slow" frequencies.
  13. dorke

    Casio WK-3000 no power on adapter but power on batteries

    Fisrt thing, Did you buy the diodes on Ebay or another Chinese source? If you did,don't rule out the possibility that you got fakes. Second, with the diode out and no power or batteries, measure the resistance you see at the adapter input and between pins 9 and 9 of JG3. In both cases switch...
  14. dorke

    Pioneer SX-SW515 - missing controller.

    Kelly, Never heard that expression before "as rare as rocking horse shit"... Rocking horses are a rarity by themselves these days.;) That's a lesson as well ...
  15. dorke

    Casio WK-3000 no power on adapter but power on batteries

    If you get 12v across the diode with the marked polarity ,anode positive. Then you have a faulty diode(open). Lift one leg, and check to verify it is faulty in diode test mode of your DMM.
  16. dorke

    Op Amp with a/c output

    You should define the "shape" of the AC signal, as well as it's frequency and amplitude. If you have a photo of how it should look like that would be great.
  17. dorke

    Casio WK-3000 no power on adapter but power on batteries

    Like so:
  18. dorke

    Casio WK-3000 no power on adapter but power on batteries

    Please measure the voltage on D202. You should get about 0.5V,anode=pin2 (+). Just to be on the safe side, You should get 12vDC on L202 between pins 1(+) and 3(-) Dave, D202 is a series blocking diode to prevent reverse polarity connection of external DC adapter.
  19. dorke

    Led volt & amp meter broke capacitor

    Well, Please take a good quality picture of the cap. and the SMD part near it. It is a tantalum capacitor(probably at the output of the SMD LDO) which we can identify from what is written on it. I suspect it isn't the only burnt part.
  20. dorke

    Digi pot for pwm board

    The largest value they make is 1M. If that alone isn't enough you can use a dual device(2 in series) to get 2M. Look here
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