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mvs sarma

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Posts posted by mvs sarma

  1. Hi again :) There is the circuit in ".png" Format.

    hi James Bond O ,
    you may have to indicate the  error image and  to members.
    Otherwise, getting some error message doesn't appear a good way of reporting.
    you can capture the screen and  upload as  .png.
    it helps  proteous gurus to study and comment.

  2. I'm looking for the part number for the SMD component with the code 31-OQ written on it (the O and Q have a minus sign on top of them). Its a 6 pin device in a SOT 26-3 or SOT 363 package (not sure of the dimensions). it is used in the power supply section of a MP3 player circuit (seems like some kind of a switching supply regulator circuit). In the circuit this components keeps over heating and the battery drain increases considerably which reduces the operating time. Any idea what it could be.

    Any link or website where i can look for SMD codes?

    thanks in advance   

    all the best.
  3. ..........
    My Toner is from Brother, but I'll try the 170-180 range & see what happens.
    All I have is a plastic rolling pin, but I'll try ooooooooooh ab out med pressure on the iron next.   Only an inkjet printer is my 2nd one, my toner melts, maybe the phone book/heat/pressure is my problem.  I'll try an old Jeg's or Summit Racing Equipment catalog, that should work.  Thanks again.


    could you spend little time to see the video from the link below

    the finer details and paper comparison are available at


  4. I've tried the toner transfer method 5 times now, 2 times, on regular paper, 2 times on tracing paper & once on photo paper & everytime the results are the same, half the toner stuck on the board, half on the paper.  I put the image on the pcb & secure it in place with masking tape, both sides, since my design uses a 2 sided pcb.  press down on an iron, tried high & lower heat settings.  Put it in water & let sit, tried letting the board cool down on the photo paper & tried hot board straight into water with the other paper attempts.  There is obviously something I'm doing wrong.  Can anyone please help me with this??  ???  It's driving me insane.  :'(


    you need a proper understanding and also patience.
    every time you change one or other item,then you will never know what mistake is being committed.
    try to use magazine paper or the type of paper used by RS components catalog.
    even text printed paper would work
    the ironing should better be done at 170 to 180 deg Celsius , and never more than that.on a Philips  make auto iron i am told that it works on polyester clothing. this setting may be valid for others also.

    most  important is the contamination free copper surface.and reasonably scrubbed by 3M scotch pad and washed and cleaned by a fresh paper napkin as cloth may gain contaminate it.

  5. We use a CRT setup as a part of our experiment for our students to calculate the e/m ratio of the electron. The experiment is usually referred to as finding e/m ratio using magnetic focusing. The supply to the CRT seems to have some problems and the setup is quite old and no circuit diagrams included. the setup uses a HITACHI oscilloscope CRT. the only thing mentioned on the CRT is TYPE no:95CB31. I was planning to repair the setup but need the CRT pin outs and specs like the heater voltage, current.
    Any one having any idea about this. could not find any thing on google.  ;)

    Once you know the Oscilloscope make and model, your user manual will have a schematic for it, where the data for CRT base pins can be retrieved.
    further, most Oscilloscope CRTs have similar specs for the same size.
    if service manual is needed  to get this data perhaps it can be had from say, http://www.eserviceinfo.com/downloadsm/11578/Hitachi_V-425.html

  6. Hey can anyone recommend a on line source for electronic components, that has small or no minimum order requirements and ships in a timely fashion? I really cant be buying a thousand diodes every time I need one or two.
    Thank you, plumber.

    For 1 or 2 components of general avaialbility, you should rather go to local seller
    or arrange with him
    any international seller would insist om MOQ per line item
    you have not indicated your location
    suppose, in my country, i get a 7805 for say 0.1$ equivalent.
    same when purchased on line costs me 27 (2+25for postage thro courier)

  7. hi,

    i am fairly new to all this so please excuse my lack of tecnical knowledge....

    I am trying to design a device to gate the output of a function generator. The generator output is sine at 2vpp ac and needs to be varied between 3 and 5Mhz.

    I have designed the 555 timer at the values: 1330hz at 25% duty cycle and i need to use this timing to gate the ac signal from the function generator (25% on 75% off).

    i have been looking at using cmos chips to do this but these only gate dc signals right?

    can you guys offer me some options/help in gating rf ac frequencies.

    incedently the gated signal with be amplified to 15w using an rf amp (not yet designed) if this matters at all


    You may consider 74HC4066. the datasheet can be studied for further details

  8. My privacy options are set to medium. No cookies are blocked.
    Today I could not get completely into this site on my first try but I could close it normally. I got in quickly on my second try.

    All other sites do not have this problem of intermittent access.
    I think the server here has some dead ports that I get into randomly.
    While I understand your IE8 based issues.  The site management also can do their bit perhaps. How ever, you may check for Virus cleaning  by using some popular antivirus, on our part of end users.

    I feel sad for the great loss of data pooled by lots of effort, over few years. I wait in anticipation of any good news . Perhaps the site admin may consider to load an earlier back up that might be still good instead of starting the calender ( of the site) with Jan 26th 2009.

  9. It happened again just now with IE8:
    1) I couldn't get in but instead got the backdrop showing the faint blue schematic. Then I tried Refresh and IE said "not responding".
    2) Again I got the backdrop but tried to close IE. IE said "not responding".
    3) I got in. I scrolled halfway down the home page then IE said "not responding".
    4) I got in with Firefox and surfing worked well.
    5) I got in with IE8 and surfing worked well.

    I don't have any problems with any other site.

      check your privacy options  under tools_ internet options  for IE8 please.

  10. If you don't mind the aesthetic views of it, you could try replacing it with a simple rotary switch.

    perhaps the O P needs a movement not rotary switch.

    Generally the helical spring burns off, if used in wrong range. May be, it is better to call it  dead , than further investing on it , and may be , if the O P likes, he may switch over to some auto ranging type 3.5 digit DMMs instead.

  11. Hackers hit the forum and injected malicious code on some files. I have cleared forum files and everything seems to be safe now. Soon Electronics-Lab.com site will be marked as safe from Firefox.

    Did you still experience delay when typing?

    Thanks Mixos, the admin.
    we had issuess of unable  to land using FireFox  till perhaps yday afternoon( Indian standard time=UTC+5.30)
    Same time we are able to land using IE8 from India. Today , Firefox is also normal

    Thanks again !!

  12. hi

    how to find the value of the IFT coil???

    i c a red color plastic or an grey color how to identify it ???

    There are umpteen number of IF Transformers in market as replacements
    Companies have their own designs. If you are talking about identifying the front end, the middle and out put  IFT identification, they generally follow Yellow, Green and white.

    Ohterwise , if you are talking of Inductance value by color strips painted on them, perhaps you need to follow the manufacturers datasheet .

  13. Look at the graph of voltage and discharge time for an Energizer 9V alkaline battery at a load of 53mA (my FM transmitter's current).
    In about 2.5 hours the voltage drops to 7V where a 78L05 fails to regulate. But it still can power a low dropout regulator for an additional 11.5 hours.

    After that point of reaching 7V, I doubt that the said battery would have have capacity to drive the output transistor , through it might still drive the small needs of the LDO output load.

  14. The LM2936-5.0 will work down to 5.2V.

    The LM7805 will work down to about 6.5V with a low current load.

    while considering LDO regulator with 9V battery, i fear the  reason that even if the battery comes to 6V or so, LM2951 would regulate-- is not justified. A 9V battery discharged  till 6V can't deliver any useful load. thus 5.2 as Input from a 9V battery  imagining to serve the circuit  can well be forgotten

  15. hi

    ok chill hero999...
    why i am asking is that i have those components with me so that is why i was asking about that circuit....kindly help me out to do this circuit....
    i cant get LM2931A...is there any substitute ???

    you get LM1117-5

  16. How can i use the clock generated from gps to synchronise a digital circuit?

    you need to phase lock your local oscillator to the 1 sec pulses that are output from the GPS receiver, by using proper divider ratio.One such article came up on silicon chip magazine of Australia in may and June issues of 2009.


  17. the power supply comes with overvoltage protection, why it is still havin AC noise?

    while Hero999 already indicated, i would like to add that the electrolytic capacitors have a life time
    and they deteriorate. At times, we see capacitors  with a bulge on their top, a definite indication of its failure. I know of service Engineers in India, prefer  to change all electrolytic capacitors as a batch, with same type and quality. It extends the life of the power supply, provided, of course, the Main and Aux transformers did not deteriorate.
  18. Hi AN920,

    Yes you definitely rocked the design.

    As i have  finished making few PCBs,  i may have to modd them manually.

    One observation -  you may  replace the modified schematic by changing the term Vcc on the collector of the modified darlington to +9V Dc .. this would be more appropriate after such nice improvements suggested.


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