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  1. dorke

    Can I repair this PCB ?

    oolong, Since they are the same diameter,the only factor is not create future short . For very short trace fix use the bare wire. For long "jumpers" use the isolated ones. BTW, excuse my french Mais pourquoi ces't marxiste cochon ?:rolleyes:
  2. dorke

    Simple LED timer circuit

    wingnut, here is another little "improvement" idea. Since the 40106 can work with a supply voltage down to 3V (the 74HC14 down to 2V) You can squeeze the battery life to very low voltages. The LED illumination would vary a lot in the range 3-6V. So you need a way to control it as the battery...
  3. dorke

    Use a ground pin as a switch

    The BMA250 looks like a very interesting little gadget... There is no max current ,only a typical 139uA, you can call it a sub ma device. Ben, what pins are you planning to switch VDD and/or VDDI ? In general, ZTX705 isn't suitable since it is a darlington. ZTX558 is fine. However, The best...
  4. dorke

    Simple LED timer circuit

    O.K, that's how it should be !:cool: Not only is it impressive , you got yourself 0.7/0.001=700 times the number of battery life STBY days. That is the power of CMOS... Furthermore ,If you can use a 2ma LED, it would be the most life you can get from the battery. You can try lowering the...
  5. dorke

    Need help repair dead switching power supply

    You are correct about the SB240 a "schottky diode 40 Volt 2.0A". You need a schottky diode for replacement. Don't know what LT116 is. The 2A05 (si diode)is not good for replacement because: 1. Vf to high 2. si, too slow
  6. dorke

    Simple LED timer circuit

    Something is still wrong ,the STBY current of 1.3ma is way too high! You should get no more than a few uA(a factor of 1000 down!). I guess you didn't tie the unused inputs to GND or VCC...;)
  7. dorke

    Simple LED timer circuit

    wingnut, Glad to hear that. what values have you used ? You can shorten the "press time" by using a lower R3(say 22 ohm) It is a "game of balance" with battery life.
  8. dorke

    Simple LED timer circuit

    Dont know what GDF543 is. The 74LS series draw too much STBY power . I would test the circuit with the CD4069UBE: 1.with "parallel" INs and OUTs. 2.use a 5ma LED or less( if you have a 2ma one even better). You will not get the proper illumination you need, but just test the circuits...
  9. dorke

    Simple LED timer circuit

    The LED you are using isn't very efficient . It is a 20mA /2000mcd /20deg one. Your original circuit suggest you are operating it at about 8mA and lower. Is the illumination intensity and angle you are getting enough?
  10. dorke

    Simple LED timer circuit

    "I assume that R1 leaks away current/voltage till it drops to a level below what the chip recognises as an "on" voltage, at which point, the output changes post-haste" Yes basically, put a bit differently: C is discharge through R1 till the input voltage is below VinL of the inverter , causing...
  11. dorke

    Simple LED timer circuit

    Non of them will do: The 4000 series because of poor output drive. The op. amps and comparators because of to high "STBY current" Have you got any MOSFETs?
  12. dorke

    Simple LED timer circuit

    Wingnut, Have you got any 74HC series "combinatorial " (Gates ,MUXs etc.)chip on-hand? If you do , the circuit can be slightly modified for them to work properly . Almost any can do a better job than the 4000 series.
  13. dorke

    Simple LED timer circuit

    Colin, "RUBBISH", care to explain or just be rude?
  14. dorke

    Simple LED timer circuit

    Wingnut, The CD4069UBE has very limited output drive capability ,hence it isn't a good choice. Assuming a 5ma LED , you should wire all 6 inputs and 6 outputs in parallel . About R3, It is in the correct location as it's purpose is to limit the initial current drown from the battery at the...
  15. dorke

    Resistor inside a fuse?

    Saucey, That is just a time-lag (slow blow fuse). Look at the markings "63mA 250V" There should be a "T" or "TT" mark left to 63.
  16. dorke

    Simple LED timer circuit

    Your two requirements: 1.max Battery life 2.no dimming of led light the solution: Use a CMOS Schmidt trigger inverter. The best results for long battery life will be achieved with the NC7SV17 Tiny single inverter in a pack. I think a 3.6V rechargeable battery(in a socket) will be a good choice...
  17. dorke

    Simple LED timer circuit

    O.K a "push-button". What parts have you laying around? resistors,si diodes,zeners about 3V. The circuit can be improved and ,meet your needs...
  18. dorke

    What is this called?

    They are called "Grabber Test Clips" . What are you going to hook them to? they come in various sizes from MAXI to MICRO. A word of caution: You may buy cheap stuff from Ebay , mostly very poor quality(got for hobbyists) . If you need professional/reliable test clips get them from POMONA .
  19. dorke

    Simple LED timer circuit

    "Bell switch" ,is this a bell- door project? If it is ,why operate from a battery? Do you do this with devices you have on-hand? If you are, any Si diodes or any Zeners about 3V ?
  20. dorke

    Bose amplus 100 amplifier weird noises

    Forgot to say :all Vdc measurements to Analog GND. and,Here is the Circuit
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