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  1. dave9

    Add LEDs to main power line

    ^ I agree that 2mA to 5mA would suffice for an indicator light (in all but bright/outdoor use), but the text was about lights, and two LEDs in the last post, so I presume the desire is to make it brighter than usual. A typical 5mm encapsulated LED is a 100mW part. That assumes good...
  2. dave9

    Add LEDs to main power line

    Why do you need two LEDs? You can use two if you want to. No you do not wire them in series with 12V PSU output. You wire across the PSU positive and negative output, from one to the other, a series of LED - 2nd LED - 1K resistor, or across the positive and negative you could do LED1 - 1K...
  3. dave9

    Add LEDs to main power line

    Why would it blink? If you're using a 12VDC power supply all you have to do is wire the LED across the power supply output, with a series resistor whose value depends on how bright you want the LED to be (within its max current capacity). For example a standard 5mm red LED, with a 1K resistor...
  4. dave9

    Add LEDs to main power line

    If you supply a schematic of the circuit including details of the power supply or at least link to more info about the radio, someone could better advise about where a good place is to tap into the circuit for the LED and series resistor. I mean that as a visual indicator that it's turned on...
  5. dave9

    HP Printer doesn't work anymore

    Do this: https://support.hp.com/us-en/document/c01458034
  6. dave9

    Wrapping Exposed USB Drives With Electrical Tape

    If by lost their containment you mean that they are exposed circuit boards with the USB connector soldered onto the end, I would be concerned that either electrical tape or heatshrink tubing does not provide sufficient mechanical strength and that they will eventually become damaged. Instead I...
  7. dave9

    Choosing a complementary transistors pair for a class B amplifier

    Might be cheapest to get something off ebay, taking whatever you can find even if they're massive overkill for a mere 2W. Then again a discreet design for 2W seems like overkill to me too, instead of some ready to roll chipamp IC with the transistors already in it. You can get a whole amp...
  8. dave9

    Wanted: Practical Analog Electronics for Technicians by W A Kimber

    https://www.amazon.com/gp/offer-listing/0750629525/ref=dp_olp_all_mbc?ie=UTF8&condition=all
  9. dave9

    What specs are the most important when swapping transistors with another type?

    What amp? Consumer or (boutique or really old) Is this amp entirely discreet or with a precision feedback loop? If the latter, you can stuff just about *anything* in so long as you get NPN/PNP right. Overgeneralizing, fewer, higher power handling transistors have reduced treble definition...
  10. dave9

    I did a hack to a Sony watchman and now it’s continuously drawing .018 amps

    It could start reverse charging the weakest NiMH cell(s) in a series once they reach 0.0V first, so yes it would be best not to let it drain down to nothing. As far as a low current cutoff, how would it know it was drawing low current unless it was drawing current instead of being cut off? If...
  11. dave9

    How to build a Wi-Fi Extender?

    Besides what davenn already wrote, it's an inappropriate project for an electromagnetism course. How about constructing a solenoid water valve to water plants based on soil moisture level? That seems a mountain easier to climb and puts magnetism at the heart of how to get a thing done (water...
  12. dave9

    schumacher se-5212a charger

    I'm sure I could figure it out if it were sitting in front of me, maybe across the internet from pics too but those have too much contrast and the thing sorely lacking is pics from further away so the whole thing is seen as a whole, top down and on each side. However, the two most likely points...
  13. dave9

    LED street lights

    Yeah, many LEDs and what it looks like depends on who made the LED(s), the carrier, and the entire light. Generally it's going to be modules of several LEDs on metal mPCBs, bolted/screwed/riveted/clamped/whatever to the heatsink which is more often integrated as the cast metal housing.
  14. dave9

    I did a hack to a Sony watchman and now it’s continuously drawing .018 amps

    As far as seeing that flat green regulator or 'fet, it could be handy to have a link to exactly where it is in the video or a standard high res picture as the video looks a bit dark to me (tho' could just be my monitor settings). Yes you can damage an IC and cause it to have leakage current...
  15. dave9

    What kind of diode is this?

    There is only so much I can suggest without having the equipment in hand and of course not having any vested interest in it, so if I blew it up, it's no loss to me. ;) I might try to determine which line going to the board (connector) is power, ground, and signal, and see if the signal problem...
  16. dave9

    How does a switch mode amplifier... amplify?

    It doesn't directly PWM the input signal. It is like an opamp in that it uses a feedback loop with (either a fixed or adjustable depending on the amp IC) a voltage divider to create a lower apparent output signal (at that point in the circuit), which the PWM regulator uses to modulate the power...
  17. dave9

    DOD Mixer Power (34 V)

    It seems the world has moved on to SMPS and not so many deals left to be had for good ole E-core transformers. A ~dozen years ago I bought some that would have worked for $2.49 each as new surplus, but those days are gone. Today the main two options I'm seeing that are most cost effective are...
  18. dave9

    DOD Mixer Power (34 V)

    Not in this case. Take a look at the linked schematic. The original power supply "might" have fuse and AC line filtering on the input before the transformer, but as far as smoothing the output goes, it is just taking a center tapped transformer and sending the AC to the mixer which has its own...
  19. dave9

    Flushing my Toilet

    More description might be needed but based on what you wrote, it seems like the average small solenoid with sufficient pull force would do the job, just needs to pull a corrosion resistant [wire, cord, chain, or rod with some play or swivel joints at one or both ends] connection to the flapper...
  20. dave9

    What kind of diode is this?

    Yeah the description of what this board is supposed to do is not very useful. Try to draw a schematic of the board and what is upstream and downstream of it. As for what type, probably some variant of a photodiode. Is it only sensing ambient light or is there an emitter on the other side...
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