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mvs sarma

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Everything posted by mvs sarma

  1. Hi Aniruddha, Didi you try PCB123 .it is really nice. the software provider gets you the pcbs made as you order on him-- easy to learn-downloaduser manual it is not a demo version. you canpurchease as you need it try download here http://www.pcb123.com/pcb123download.php
  2. Hi Hotwaterwizard, the site is showing the devises sn84 series-- no doubt other sites like alldatasheet etc are dumb on these. however, may be, recently introduced. any other info and how they differ from normal 74 series-- any enlightenment possible? Regards Sarma
  3. Hi, i didn'tmean disconnect all sec connectios of smps tfmr. i only said that the load , i mean, the DC load on 20V output-- if there is a short in the load , this type of sound comes. I was asking you to test smps exclusively with an artificial load, say two 12Volt bulbs, in series to make 24 volts .or a resistor as i suggested, Sarma
  4. Hi should we now feel that the fuse is not blowing after second time soldering? coming to smps tranformers, the parameter to be checked is inuctance of the primary and secondary coils, turns ratio (Np and Ns, and cross insulation of secondary wrt primary. as you switch the rectified DC using a high frequency of the order of Few KHz, DC coil resistance has no relevance. some times when operating frequency goes to few hundreds of KHZ, turns come down to 20etc, and windings will be paralleled in order to increase cureent carrying capacity. i was asking you to test smps exclusively with an artificial load, say two 12Volt bulbs, in series to make 24 volts .or a resistor as i suggested, mean time you can check for vertical section driver IC or final stage transistors, anf the final transistorof line output for short.
  5. Hi Walid, these are my feelings with my limited knowledge. the circuit should work from a supply down upto 1.8V (2*0.9V) where after the batteries are to be replaced. perhpas you have to maintain the overall gain of the device in the battery supply range. 10k may work well atlower voltage,but with BC549C having so highgain 10K wold be improper. collector has to be main tained at near half the supply voltage as seen across C4. if 10K is used it will fall down. and the voice may be distorted. battery lifemay be shortened. 10uF in place of 1uF-- may boost low frequencies, but already limited by earlier coupling capacitors at 0.1uF. sarma
  6. Hi Try disconnect the load and give artificail load of say 1amp across 20V point and see-- load like 22 ohms 20 watts resistor BE VEY CAREFUL AND GUARD YOUR GOOD HEALTH-- THESE SMPSs are SHOCK prone.
  7. Hi. check the PIN out data for the replaced components-- whether this aspect istaken care while soldering them? what are the voltages measuredt at the respectiveTransistors?
  8. Hi walid zee, High voltages cause insulation breakdown and low voltages cause high currents and heat up the device to burn. regards Sarma
  9. Hi, did you remove the part and checked for its resistance, it may be 120ohm 20 watt resistor and used in the EHT section to generate the exrra high tension voltages.. If this is bad by a dry joint at the pcb you can mount it back it should work-- if the component burnt at the middle and blasted-- i suspect a pwer transistor with a heatsink should be also faulty-- Sarma
  10. Hi Aan, please try this URL www.dalbani.co.uk/catalogue/product_details.php?id=12370 - 32k
  11. Hi we can also use a DIAC (conducts at 32 volts in each diection) and this will reduce comonent count. component is ST micro DB xx
  12. Hi Noname, In amother TI application note "SLUS180E–NOVEMBER 1999–REVISED OCTOBER 2005", i find that R6 is not commoned . current sense pot lower portion is dirctely grounded. Next i find that the output at souce of IRF540 is to be taken with some seriies resistor to guard the un committed transistors inside 3524. then you may perhaps test in real time.
  13. Hi Audioguru, We regard you very high for the strog fundas you have and demonstrate. while so we feel some times let down by expressions
  14. Hi Noname, i have doubt on, whether bottom point of R6 tobe connected ground or to the Rt and Ct combined. In another open loop test circuit, i observed that Rt and Ct are not shorted. Also please check the collectors at 12 and 13 (looped) is referes as input to IR2117 while emitters(looped) is referred to the load point , ie source of IRF540 ? thus so you expect out put at source of is to be sensed when irf54o is off as a low signal to IR2117? the IR2117 in point has a schemit inveter followed by Under voltage sensor. How do you expect low(IRF540 OFF time) tobe able to be sent via the NPN transistors inside 3524? perhaps collectors may go to souce pin and emmitters go as input to IR2117? i am not sure but appears logical. can you give any known ref to this schematic ? Sarma
  15. Hi, Why "ALL' you could directly thank HOTWATERWIZARD who gave the data --
  16. Hi AudioGURU, Yes. i couldn't size it properly--rather i had to learn how to . let us see the utility aspect of theis element for the pupose.
  17. Hi, the third pin is generally connected to body and body itself is therwise isolated from the capacitor-- toy may check up as you have the piece acrss
  18. Hi, Perhaps explanation insufficient-- needs elaboration and a sketch , even to start thinking on it, please
  19. Hi, So, you want to test transistors while they are in the circuit.-- tell us when power in on or power supply removed? if in circuit testing is required you can test by junction voltages -if powered-- or in dide range of DMM if power is removed.-- you sshould have a comperhensive idea of adjecent circuitry for this type of testing as junction some other transistoir can be parallel to the one under test --perhpas a diode is alrady across collector emiter if you test without imagining situations like that-- you will be likey misguided as to the condtion of the device under test (DUT) perhaps electronic principles by AP Malvino may be a better book -- try it
  20. Hi, Noobies99 welcome to the forum and happy new year2k7 attched a datasheet for the IC-- study whether this helps you TEA152X.pdf
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