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  1. walid1

    very simple PS

    Thank you guru, u r  truly remarkable man
  2. walid1

    high wattage resistor in batt charger?

    Hi Why, usually using a resistor with little resistance and high-value wattage in  battery chargers circuits? why not connecting the batt directly with the source? thank you
  3. walid1

    transistor as a switch

    Hi can you explain What R8 (1K) exactly do? is it a voltage divider?? thanks
  4. walid1

    very simple PS

    Hi please look at the figure below: if as seen, the X1 secondary voltage is 6V AC, then the rectified DC voltage after the bridge and a cap (1000u/25V) filter is 6* sqrt 2 =8.49 VDC is this true, please comment. thanks
  5. walid1

    IC controlled emergency lamp with charger

    Hi guru I am very sorry, I did not notice it. How wonderful it for a zener non-existent My understanding is that the cap charged through only R3, but now I do not know how dischargting, or to any point, is it to  pin is 6 or 7 of the 555 IC. and why he do so, what shape of the o/p pulse he want...
  6. walid1

    IC controlled emergency lamp with charger

    Hi all In the attached file below u can find the circuit diagram of the IC controlled emergency lamp with charger my question is what the purpose of using D5 and D8, what they do in the circuit?? thanks
  7. walid1

    Adjustable precision shunt regulators, TL431

    Hi I have another question about the shunt regulator 431: We Know that Vout = (1 + [R1/R2]) * Vref If I want Vout 12.5V and assume Vref = 2.5V then 12.5/2.5 = 5 that is R1/R2 =4 400K/100K = 4 4ohm/1ohm =4 ???!!!!! I read three different 431 datasheets from three different companies trying to...
  8. walid1

    Adjustable precision shunt regulators, TL431

    Thank u guru No problem, I didn't calculate it, only I put random numbers to know the value of Vref, you are clearly mentioned in Your previous answer I got what I want Thank you once again for your attention.
  9. walid1

    Adjustable precision shunt regulators, TL431

    thank you guru fore your direct and good answer, it was very good also thank for Ldanielrosa
  10. walid1

    Adjustable precision shunt regulators, TL431

    Hi In its datasheets attached below, and looking to the atteched figure below, we can see that: Vout = (1 + [R1/R2]) * Vref If +V = 12v, R1 =10k, R2=2K What is Vout I cannt understand how to get Vref value please help me to solve this thanks 431-2.pdf
  11. walid1

    transistor saturation

    ok thank u guru
  12. walid1

    transistor saturation

    hi guru You did not understand me, so I'll ask the question once again : The 2N3904 transistor have the following char. from datasheet: Po = 625 mW Ic max = 200 mA VEC max = 40 V from that, if we have VCE = 5V, the max IC = 625m/5= 125 mA Now if at saturation, VCE=0.4 V, then Ic max = about...
  13. walid1

    transistor saturation

    Suppose that You used a transistor 2N3904, in its datasheet I found that the Po = 625 mW; the power which this transistor can dissipate (in the form of heat) equal to 625 m Watt. Now, if we assume that VCE = 0.4 V at saturation, this transistor can pass to 1.5 ampere as Ic. But in the datasheet...
  14. walid1

    Computer power supply question

    Brothers hurt, the most important stage in the Computer power supply is the input stage
  15. walid1

    Crystal examiner

    point me please
  16. walid1

    Crystal examiner

    Hi often have some friends with their remote control to to repair it. This requires that you have the examiner Cristal to ensure the validity of this piece. In the past, I was immediately replaced them with new, but I know I need to examine the crystal. Searched in the internet and I found this...
  17. walid1

    Help me to understand the MC3359P IC

    Hi guru thank you for fast reply In my country, there is a puplic open market, they sold scrap, half a telephone 1/4 radio part of vedio recorder..etec every month, i go to this market any by some boards i have this 1/2 phone, it is senao, it is at least 10 km long. After this discussion with...
  18. walid1

    Help me to understand the MC3359P IC

    Hi guru Ok, I understand that you have never looked inside one before and u have never seen a schematic of a narrowband dual conversion FM receiver circuit before. But also I know that u still have the ability to help me. I need you theory information to help me in my trip inside that cordless...
  19. walid1

    Help me to understand the MC3359P IC

    Hi guru As you know if u click on th followin image it will become bigger http://www.electronics-lab.com/forum/index.php?action=dlattach;topic=9699.0;id=6451;image can you please tell me where the TX to draw it thank you
  20. walid1

    Help me to understand the MC3359P IC

    Hi guru dont worry I'll draw the schematic and discuss it with you. I can do it, u  help me, we can do it. now i'll draw the Rx (3359) and related parts and put it here, then u tell me where the TX part I see the two LM567CN, i know they are for tone detection I'll draw all pars in sequance and...
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