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  1. dorke

    Need help choosing capacitors

    Yes like all newbies have to. But seriously, Try and calculate the max power you can achieve with a 24V power supply and assume you have an 8 ohm speaker. This is the very basic and essential understanding of Power Amplifiers. Show how you did that . Don't be shy,we all learned (and still do)...
  2. dorke

    Osillascopes?

    Absolutely,as long as the signal frequency bandwidth is lower than the vertical bandwidth(actually it should be 1/5 of it !). Here is a paragraph from my favorite ORACLE of scopes Tektronix (page 35): "Without adequate bandwidth, your oscilloscope will not be able to resolve high-frequency...
  3. dorke

    Need help choosing capacitors

    Steve,How so? Must be the late hour (mine or yours);)
  4. dorke

    Basic circuit help

    A side note: The circuit you just designed is the basic 2 input or gate. So welcome to the world of digital electronics;)
  5. dorke

    Osillascopes?

    Adam not really, I have seen DSOs with 1Gsa/s(and above) and A bandwidth of 100Mhz(or less). You can only use them to measure signals with spectrum less than the vertical input bandwidth . Useless for higher frequencies, although you can see the error-ed measurement at a resolution of 1nSec.;)
  6. dorke

    Need help choosing capacitors

    Welcome to EP. The issue of choosing capacitors has much more issues related than "keeping them safe"... What are your design goals in terms of RMS power? You see a 24V PS will not get you very far... can you calculate what power you can get with it? Hint :a lot less than you think ;)
  7. dorke

    24V dc to 12V dc battery charger

    Welcome to EP. 1.The PNP BC557 is simply the LED driver(on to indicate battery fully charged.) 2.The diode 1n457 is there for the purpose of letting the LM301 output influence the LM338 only when the LM301 output is in the it's "-Vsupply state"(i.e close to GND). 3.The lower 15-ohm is part of...
  8. dorke

    Function Generators / test probes

    Welcome to EP. For audio gear you don't need a function generator. What you need is an Audio signal generator. The cheapest thing is a "software" one which costs nothing. You can buy adapters from many vendors on the WEB. Or you can build them yoursel. You must be very careful with XLR...
  9. dorke

    Thermocouple RF Ammeter

    For SWR monitoring BIRD has the model 4342 Dual meter. With scales for foreword/reverse and SWR scales Very nice dual needle movement;).
  10. dorke

    Osillascopes?

    All scopes aren't equal ,far from it ,there is a big verity to select from. Sa/s doesn't mean much, what is more important is the input bandwidth. For audio you don't necessarily need to buy a scope ,you can use a software one for free. Define RF,and powerful amplifiers.
  11. dorke

    Help with Sony slv-n750

    The VCRs are obsolete tech, I think no body makes them for at least 10 years . Hard to recommend one,you can probably buy them for next to nothing 2nd hand. The biggest problems are belt failure(they are hard to find). The big names were JVC,Sony and Toshiba
  12. dorke

    Thermocouple RF Ammeter

    The Bird 43 is an outstanding engineering item . So well build and excellent for the job, practically sells the same product from the beginning ,about 65 years back. That is truly an amazing thing for a test instrument. The directional-couplers and SWR bridges are not only used by hams. Many...
  13. dorke

    Thermistor ID

    You can find the part (may be hard to get just one) at: digikey Mouser octoPart Make sure you know why the part blew before you replace it. No short circuit or other defective device.
  14. dorke

    [novice] MOSFET not turning on

    The 12NF06L is a 60V/12A beast, why would you use it to turn on a tiny LED? What kind of LED are you using(color and mA rating)? Do what @Patrick123 suggests : Move D1 and R2 to the Drain and connect the source directly to GND. BTW, R2 seems a bit to high.
  15. dorke

    Thermistor ID

    Welcome to EP. You have a PTC ,it is used in the input (mains circuit) for over-current protection. It exploded because of an over-current condition (possibly a short ,check that this isn't the case). If your unit is 110V the part you probably need is: TDK(EPCOS is a part of them nowadays)...
  16. dorke

    Keeps blowing circuit module!! :(

    Well, your photos show that bob was correct. The 3.5mm is indeed the speaker connection(not headphones but the speaker itself). And it probably is mono(!) There is a workaround like so: Identify the Audio Power amp IC remove it from the board and connect the 3.5mm to it's input(s),other things...
  17. dorke

    Keeps blowing circuit module!! :(

    What Bob says makes sense only if you have connected to the modules speakers pads(marked ±v and clearly shown as the speaker connection in the photo). However if you connected to the 3.5mm Jack,clearly this isn't the cause of the fault. Another important note : If you are only going to use the...
  18. dorke

    Using PWM to regulate power dissipation

    When you do check that generator again do this: Disconnect all loads to it (capacitor included). Measure it with no load . Then use a pure ohmic load and measure again. Find out what is the power capability of the generator. Find out if it has any voltage stabilization circuits and what they are.
  19. dorke

    Keeps blowing circuit module!! :(

    Welcome to EP. Can you please post a clear pic of what "transformer" and 12-5V you are using. I guess, if it's 12V/5A must be a SMPS type,they can be very noisy and probably the 12-5V another SMPS (?) has problems copping with what they produce. What is the "microchip" that blows,anything...
  20. dorke

    Another new guy

    Welcome to EP. Dan, you have quit a shocking and disturbing Avatar. Without entering into views and politics, please change it to something the eye can watch. Thanks
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