Jump to content
Electronics-Lab.com Community


  • Posts

  • Joined

  • Last visited


Everything posted by smokyLED

  1. I'm trying to find a replacement for an IC in my frequency counter. It's a 8 pin DIP, and could possible be a opamp. But i'm not sure. I have googled but haven't had any luck. This is with is printed on the package: TFK 731 666 BS TFK666BS seems to be the product code. Thanks in advance.
  2. anyone have a user/service manual for this? my channel b shows random values even when there is no input.
  3. what is the best way to heat up used ammonium persulphate? i store it inside a plastic bottle after using it, and i don't want to put it in the microwave.
  4. i've tried the photo paper method, but fine traces doesn't stick to the pcb very well. transparency film work great though, as 98% of the toner comes off. all u have to do is touch up the missing traces with a pen.
  5. nah, the bands are correct, but the resistance was 2k ohm, even though it's a 1% tolerance resistor.... i'll remember to check resistors with a meter in future, instead of relying on the markings
  6. you should post of picture of the 15hp motor installed in ur car :D
  7. replaced the 10k resistors and it works now. what is the point of having TY1 and SW2, when TR4 already provides current limiting by shorting IC2's supply to ground. There doesn't seem to be any short circuit protection in this circuit... because when i short the output, current limiting kicks in, but i can hear buzzing.
  8. buck regulator or a flyback regulator with a tl494 maybe?
  9. here's an example of a pwm to contorl a motor, http://www.dprg.org/tutorials/2005-11a/ otherwise the 555 datasheet might be useful, http://www.fairchildsemi.com/ds/NE%2FNE555.pdf
  10. pin 4 and 11 is connected. i get full rail voltage at pin 1, and there is a voltage on pin 14
  11. yep, just what i thought. but it still doesn't work. i've triple checked the wiring and components and tried different LM324. still doesn't go high when there is a difference.
  12. I have built this circuit, and i can adjust the voltage and current correctly using the pots. However the current limiting and temperature cutout doesn't seem to work. I am getting no voltage at pins 7 or 8 of the LM324. PARTS TF1 230/24V 100VA transformer F1 1A fuse F2 6A fuse SW1 on-off 250Vac SW2 on-off switch TS1 240V on-off switch M1 Panel meter 5Adc M2 Panel meter 30Vdc IC1 LM 324 quad opamp IC2 7812 jänniteregulaattori +12V D1 1N4004 D2 - D6 1N4148 tai 1N4448 tai vastaava D7 1N4004 D8 Zener diode 6V 1,3W D9 LED  D10 LED D11 LED  TY1 TIC47 thyristor TR1 2N3055 transistor TR2 BD237 transistor TR3 - TR4 BC547 transistorC1 Elektroi 4700uF 40V C2 Polyester 220nF 63V C3 Elektro 100uF 40V C4 Polyester 100nF 63V R1 - R2 1kohm 0,25W R3 - R4 10kohm 0,25W R5 3,3kohm 0,25W R6 1kohm 0,25W R7 33kohm 0,25W R8 10kohm 0,25W R9 470kohm 0,25W R10 - R11 10kohm 0,25W R12 33kohm 0,25W R13 10kohm 0,25W R14 - R15 10kohm 0,25W R16 - R18 1,5kohm 0,5W (or 2 series 820ohm 0,25W) R19 Potentiometer 47kohm LIN R20 Potentiometer 1kohm LIN R21 Trimmeri 10kohm R22 Trimmeri 1kohm  R23 NTC 1kohm R24 0,3ohm 5W The original design is from http://koti.mbnet.fi/~huhtama/ele/index.php?si=kyt01.sis&pa=j
  13. yea it's all good now. just needed a cap across the zener. i'm using a bridge rectifier instead of the 4diodes
  14. got it fixed. stablized the zener voltage by sticking a 47uF cap across it
  15. ok, it seems to work a little now. the input voltage slowly drops and the voltage across the zener slowly rises. didn't measure the voltage for long enough before to see this happen. but with only a voltmeter connected across the zener and ground, the voltage seems to drop by itself. once it hits zero, the voltage doesn't rise back up unless u connect the voltmeter between the input side of the 82 ohm resistor and ground. how does a charge pump actually work?
  16. wierd thing about that circuit is that i'm not getting any voltage across the zener diode
  17. oh, the whole circuit was powered by a bench supply @ 35V 2A (current limited) the -6v is fed from another 10v transformer feeding a 7805 regulator. the ground pin of the reg is connected to the -6v, and the output is connect to the circuit's ground. is there a better way to do this, like using the same supply as the circuit?
  18. thanks audioguru! ;) so i'd have to run 2x 2955 in parallel with 0.47 ohm resistor. 5W variant? and change the base resistor to 2 ohm 5W i was testing with 12V before.
  19. I'm making a bench supply out of the 5A Constant voltage/current circuit on page 16 of the LM317 datasheet http://cache.national.com/ds/LM/LM117.pdf. I've replaced the MJ4502 transistor with a MJ2955 TO-3 transistor. Thing thing works fine for current up to 1A, adjusted via the pot. But once u put a load on there with current adjustment more than 1A, the 2955 transistor just shorts out and dumps the whole 5A across it. If u leave this going long enough it smokes the 3.3ohm resistor as well. I find this strange since the transitor is rated to 15A, and the circuit is meant to go up to 5A (though i've only supplied it with 2A max while testing). I've got the transitor on a small diamond shaped finned heatsink, though this seems insufficient. Is this my problem? Also for short crcuit protection, diodes can be added to the circuit. Namely diode acoss the out and input of the 317 regulator with the negative end connected to the input, and another across the adjust and output - negative end connected to the output. This circuit lacks these diodes, so I take it that is is not short circuit proof? Whould I be able to add them into the circuit without affcting the operation of the opamp for current limiting? Should the 3.3ohm resistor be more then ur standard 1/2W variant? i.e. 5W
  20. ok, who's gonna sell me a pcb with the update design? ;D
  21. where can i buy the pcb from? it is hard to make it myself, since i hae no where to dispose of the chemicals. what can be used to replace the 2n2219 transistor, and cna the TL081 be replace with a TL071
  • Create New...