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  1. KrisBlueNZ

    New To The Forum

    Hi Jon! Welcome to Electronics Point :-) Hope to see more from you in the future.
  2. KrisBlueNZ

    Harman/Kardon HK6500. Loudness not working when button is pressed

    These other transistors that are overheating could be the reason why the power supply rail voltages are low. They're on PCB 6, the equalizer board, in the phono input section. You can just disconnect the wires from CN403 on the main board. You won't even need the phono circuitry unless you have...
  3. KrisBlueNZ

    Harman/Kardon HK6500. Loudness not working when button is pressed

    OK. Did you insulate Q519 and Q520 from the heatsink? If not, that will be why R555 and R556 are going up in smoke. If you did, there may be a short on the output of those regulators. Can you find CN401 and CN402. They should be near Q519 and Q520. CN401 connects to the tone control PCB and...
  4. KrisBlueNZ

    I2V Converter Circuit

    A 7805 is not accurate enough either. You need a voltage reference, not a regulator. Here's a circuit using a TL431 which has a nominal voltage of 2.495V. For best accuracy use an A or B suffix device. Accuracy is also dependent on resistors RA, RB and RF1. If it doesn't work as expected...
  5. KrisBlueNZ

    Harman/Kardon HK6500. Loudness not working when button is pressed

    Good. Good. I think there's probably a separate problem that is causing those transistors to overheat. It's unusual that both channels would have the same problem, so I suspect it's something common to both channels. It may be related to the low power supply voltage. I doubt those eight...
  6. KrisBlueNZ

    clocks of ic-74LS95

    Just the satisfaction of helping a fellow human being solve their problem :-) "... for the children." -- Lawrence Jamieson, Dirty Rotten Scoundrels
  7. KrisBlueNZ

    how to calculate battery parameter for this

    Where does the 3600 come from in that equation? There are 24 hours in a day, not 3600. There are 3600 seconds in an hour, but that's not relevant unless you're calculating joules. When you multiply a power figure (in watts or kilowatts) by a period of time measured in hours, the units become Wh...
  8. KrisBlueNZ

    clocks of ic-74LS95

    As I said, convenience for the circuit designer. Yes, they could have done it that way. And they might have, if they didn't have enough pins. Yes, a tiny bit.
  9. KrisBlueNZ

    What breaks when you "gently" drop something?

    To paraphrase Steve's reply: Open it up and have a look! Especially, look for heavy components, and components mounted on heatsinks, and check the joints where they are soldered to the board. Also check for any moveable parts that are accessible from the outside, which may have received a thump.
  10. KrisBlueNZ

    clocks of ic-74LS95

    You've answered your own question. The two clocks are needed because they do different things. The 74xx95 shift register can operate in two different modes, as selected by the S pin (pin 6). If S is high, a falling edge (high to low transition) on CP2 causes the data on the four parallel inputs...
  11. KrisBlueNZ

    Flip flops

    Please post homework questions in the homework forum. I have moved this thread.
  12. KrisBlueNZ

    Harman/Kardon HK6500. Loudness not working when button is pressed

    If they're both on the same heatsink, and they both have metal tabs, at least one of them must have an insulating washer. Have a close look. You may want to remove the heatsink compound (white goop) using toilet paper and/or a cotton swab, and replace it with new compound when you've replaced...
  13. KrisBlueNZ

    Before all publications went through the marketing department first...

    I saw this data sheet recently for a transistor from Matsushita and had to laugh at the word marked in the blue ellipse. This was obviously published before the days when every single company publication had to go via the marketing department to make sure it was word-optimised to put the very...
  14. KrisBlueNZ

    Trying to solve a 12v D.C. Problem, Need Help

    No, I don't think so. Probably a big PTC fuse would be a good idea. Something like http://www.digikey.com/product-detail/en/LR4-900F/LR4-900F-ND/1113483 in series with the positive wire, at the main battery end. Yes, sure, I agree. Any resistance in the connection from the main battery to the...
  15. KrisBlueNZ

    Timing Circuit? Counter?

    OK, here's a better design. I've added U2, a TL431 2.5V shunt reference IC. Actually its nominal output voltage is 2.495V as shown on the schematic. The input voltage thresholds are derived from that voltage, so they're not dependent on the supply voltage. The marked values for RB, RC and RD...
  16. KrisBlueNZ

    Is this possible??

    Yes, you can get relays with 120V AC coils that can switch many amps at 12V DC. You would have to leave your laser power supply plugged in, so you can avoid the startup delay. Also I don't know whether it's safe to just disconnect the laser from the 12V supply - the supply voltage may rise when...
  17. KrisBlueNZ

    Trying to solve a 12v D.C. Problem, Need Help

    LOTS! I'd recommend a small battery - something like a 2 Ah or 6.5 Ah SLA/VRLA - local to your lighting and just connected in parallel with your main battery through an independent cable.
  18. KrisBlueNZ

    Can this circuit works What changes I have to make to Drive 1w Leds on same circuit

    What OS are you running? It runs on XP but with Win7 and later you need DOSBox (http://www.dosbox.com/). It doesn't know about privileges; it's an MS-DOS program! There's no need to "install" it, but you need to set up the directory paths to the libraries, schematics, etc, and they need to be...
  19. KrisBlueNZ

    machine language to assembly language

    The 8051 uses the Harvard architecture where the data path from the ROM (where instruction opcodes and operand bytes are stored) is independent from the path to the data memory. In general, the ROM is used only to provide instruction bytes to the MCU core, and other memory accesses operate on...
  20. KrisBlueNZ

    I2V Converter Circuit

    A zener diode is not accurate enough. You need an IC voltage regulator like the one I linked to.
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