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mvs sarma

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Posts posted by mvs sarma

  2. My amp's distorting

    in Electronic Projects Design/Ideas

    Posted

    please see the BTL aplifier application in the attached Philips Application note.
    the electrolytic cap on pin 3 is not shown in BTL application pl check

    also the input should be 1v line in equivalent  for proper audio output

    as audioguru already suggested try pre setting the vol cont of the said MP3 player for proper input to the power amp.

    next to this , perhaps i fear whether the IC is OK or Not ?


    tda1519a.pdf

  4. project help with toy IC boards

    in Electronic Projects Design/Ideas

    Posted

    i am totally in line with audioguru's philosophy-- there were times when power was generally indicated (specified) as RMS watts. --over times the pmpo took over. in fact the transformer used in the multimedia speakers is too small( if not three small) it coud deliver few ma at 12V  finally the output power could not be greater than 400 to 800 mW per channel as the input DC power is 1 watt max

    sarma

  6. need help for cfl lighting

    in Electronic Projects Design/Ideas

    Posted

    you may use 555 as oscillator and use one driver transistor like C1061 and use 6V/230V transformer [ if possible the core shall be repacked (All Es one side and all I s other side ], with a gaping paper placed between them and the whole Transformer repacked) to prevent saturation-- for oscillator you can also try cd4047b both in astable mode at say 40KHz. of course the component count will be more as compared to what you showed. Finally the CFL will not have filament drive and the CFL itself needs a modifivation in the sense that these CFLs come with a built in starters meant to work at 230v/115v AC with a suitable choke. this starter is to be replaced by acombination of 470K(0.25 W ) resister and 2n2  cap in parallel.

    many chinese make lanterns use HiTachi type 6" tube without filament pre-heating

    finally perhaps audioguru 's openion is right that the illumination may not be to the expectation??

    you may however try it out

    sarma

  9. I think I cooked my A/V Transmitter

    in Service Manuals

    Posted

    223 and 473 appear to be smd resistors as per the photo
    reg the ic marked BBHH let me try

    as the item is purcheased at Ebay  the concerned add may indicate the manufacturer and perhaps a mail req the manufacturer may help for the service data with schematic and artwork

    or even the ebay may replace the item

    sarma

  12. FM Radio

    in Projects Q/A

    Posted

    Fine-- there was a time lapse in my reverting back-- as i was out of station attending on a relation who was sick, thus not verymuch on net.

    i went thro all the letters  and also the philips application note an192

    PIn 5 of TDA7000 sits on =ve voltage thus the Varicap positioning is RIGHT

    the circuit is also checked working by andy815 with potentiometer.

      i stand corrected.

    sarma

  13. FM Radio

    in Projects Q/A

    Posted

    hai all

    plsee carefully the FM radio schemtic of the project and you will appeciate that

    THE VARYICAP IS SHOWN CONNECTED WRONGLY-- IT SHOULD BE IN THE REVERSE DIRCTION TO THE BATTERY POLARITY, ON THEN, THE DIODE WOKS AS A VARYCAP

    PL TRY OUT YOU ARE SURE TO START RECEIVING STATIONS   

    anxious to get feedback

    sarma

  17. Use a speaker as a microphone while useing it as a speaker

    in Inventive/New Ideas

    Posted

    dear audioguru,
    being a retired engr of telecom from india, i recollect that we were able to achieve a balance of say 40 db-- i do understand -- but i was only trying to think of a way loudly -- i do realise that we have to do a lot towards perfection. if something works and with a lot of zeel and patience  it coud be possible -- how ever there are other straight forward and easier models of desogning -- one need not of course stick to a single speaker doing bothe the jobs -- ok  thanks for the reply please

    sarma

  18. rf coil

    in Electronic Projects Design/Ideas

    Posted

    if it is aroud distinguhing between two cellponones ringing--RF has nperhpas less to do--all cdma or gsm technology-- setting a bit inyour phone makking it generate (simulate ringing)-- if it is only rquirement-- perhaps one could change the ring tones by selection and crate two different tones  towards ring distingushing--

    even if the request is centered around detecting signal from the air-- i fear one may not be able to use simple technics like filters detectors etc,, pardon me --

    sarma

  19. Use a speaker as a microphone while useing it as a speaker

    in Inventive/New Ideas

    Posted

    i understand audioguru and thanks to Eurobuskers--
    i really feel like realising it-- in telecom we have something called 4port hybrid-- ofcourse a pasive network. converting 4 wire to 2 wire -- if one can recall the principle involved there-- it is not a problem realising a speaker receiving signal from an adjecent port and the same working as a mike pumping into the adjecent ports as looked from the speaker-- let me analyze-  call the four ports N, E, S, &  W

    same as north,east etc

    now the recived  output may be fed from west port -- it will be distributed to N&S but minmum (null if balanced) to E port.
    the speaker could be imagined on N port  -- next when speaker ,working as a mic will output small signal from N port to equally distribute to E &W ports.

    the signal towards W is wasted --while the one towards E port could be amplified and with necessary feedback and still be used with minimum disturbance from in coming signal-- ofcourse it calls  for careful balancing of the hybrid network-- detailed explanation could be found in transmission technology of telecom fundamentals--

    these things are like challenges to youth and few of them do realise- the immposibles (so far so)

    all the best

    sarma

  20. Convert 0-30V 3A PSU to 5A or more

    in Electronic Projects Design/Ideas

    Posted

    as all of us know, in a linear power supply with such broad spec like 0-30v dc and current demand of 5 amps- lot of power is likely to be wasted-

    A) if the spec permits why not the rectified DC be processed thro a switcher and a non- isolated output is taken in a buck regulator form( as the mains transformer provides for the necessary isolation)-- of course taking care of ripple limits.

    B) whather thr primary could be controlled using anlectronic fan regulator (thyristor type)  in series to primary, the secomdary rectified and adequate filtering done to suite the needs or

    C) procure a transformer with taps at say 9V (for 0 -6 vDC output ), 18V and full-- try switch teh limb to the rectifier-- out put configured to an adj regulator with series pass and the adjustable pot also switches symultaneously-- ganged switch.

    with one of these methods perhaps we can device and still try to save on power --

    any comments  welcome

    sarma

  22. Use a speaker as a microphone while useing it as a speaker

    in Inventive/New Ideas

    Posted

    Alun,
    if cost is not a creteria, i suggest , you limit the bandwidth to 3khz, and now you try to switch the active limb of the speaker, to  Input / output at a faster rate(by some FET switches using an osc  ( say 4066). ( i mean chopper)
    thus if the switch points spkr as out put you listen and whan as input the signal goes to ip of an amplifier. of course you may have to filter the osc frequency from the audio O/P .

    i accept it as a concept  and i am sure you can take it ahead-- all the best-- i shall be happy to get feed back from  you

    sarma

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