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  1. HellasTechn

    What kind of diode is this?

    If you have a multi meter then you can set it to diode test and see if it will conduct one way side and block the other.
  2. HellasTechn

    RCA TV Back-light inverter.............

    Though not American, i would have replied. You just beat me in terms of speed :)
  3. HellasTechn

    The low quality busted headset sounds underwater effect

    Bad solder joints are probably causing it. Why dont you just replace the cable with one of better quality and save the headset ?
  4. HellasTechn

    What kind of diode is this?

    It looks like a dual diode package but without marking or some service manual then it will not be easy finding a replacement.
  5. HellasTechn

    Serial communication problem.

    Sir Chris, I apologise for all confusion i created to you. I really appreciate your help and thak you for that. That design was made by me and after lots and lots of experimenting i finally figured out exactly what is going on in that circuit. Further more the transistors where intentionally...
  6. HellasTechn

    Serial communication problem.

    I further tested and i think i came to a conclusion about this weird scopings ive got. On the breadboard i assembled the following circuit exactly as pictured and fed it with -5V from a symmetric psu on the oscope screen i got a -700mv voltage. Conclusion: the negative voltage seen on the...
  7. HellasTechn

    Serial communication problem.

    I do have one and the diodes appear to be functioning correctly. I will replace them with new just in case. Beleave me, next step would be for me to ship the pcb to you so that you can examine it for your self. :)
  8. HellasTechn

    Serial communication problem.

    Good day to you all ! I am back digging out this old thread to ask a few questions about a few things i have noticed about the circuit below. It is a Picaxe Microcontroller that receives ttl level rs232 signal from the simple transistor rs232 to ttl converter. the transistors used are BC547...
  9. HellasTechn

    Huntron Tracker 2000.

    Yes i see your point. Generally speaking, i am happy with the tracker. :) By experience i am sure ill be able to detect faulty components faster specially by comparing boards.
  10. HellasTechn

    Huntron Tracker 2000.

    :) Yes i understand. In the case mentioned above i used two single capacitors of the same value and voltage (removed from the board). One was bulged and the other was good and like i mentioned before the difference was barely noticeable. If it wasnt for the bluging, i could have mistaken it as...
  11. HellasTechn

    Unknown component

    This is indeed a capacitor. I have seen them in older audio amplifiers. Probably a paper capacitor. take a look here : https://electronicspani.com/types-of-capacitors/ indeed i have never came across a faulty one.
  12. HellasTechn

    Please Help in circuit repair

    Google search reveals that the VTR 07511 is a Metal Oxide Varistor. I think you may be able to use a similar characteristics Varistor (that would blow at about the same or lower pick voltage). BUT rest assure that if the Varistor (TVR 07511) is blown then you definetly have a burned mains fuse...
  13. HellasTechn

    Added a second battery to my tablet

    I hear ya but still i am not sure...
  14. HellasTechn

    clicking from main board on a panasonic TX-42AS650B smart tv

    I recommend that you get a digital multi meter and set it to diode test, then check all diodes you can see on the PSU. You may by chance locate a shorted diode that triggers the protection. If not then you have wasted 5 minutes of your time. :)
  15. HellasTechn

    Added a second battery to my tablet

    I understand your point. The question now is, how the device sense remain battery percentage ? Most tablets calculate remaining battery percentage based on battery voltage. The app on such device will not read that the battery is say at 100% if voltage is not at 4.2 Volts. Now two batteries of...
  16. HellasTechn

    Added a second battery to my tablet

    If you have the batteries connected in parallel then it does not make sense to have the same battery life. If in parallel then the batteries have to be of the same mah rating, then in the same charge level e.g. both empty before you connect them on the mainboard. Then charge them to full...
  17. HellasTechn

    Wanting help fixing bench power supply.

    Isnt there some model number or something ? Anyway i suggest that you check the power transistors that are most probably attached to a large heatsink. Some Power supplies use the 2n3055 transistors. They usually are the first to go when shorting the output. also you should check any voltage...
  18. HellasTechn

    Huntron Tracker 2000.

    Capacitors ESR is directly affected by the capacitors voltage rating. Anyway even on the tracker the measured 850uf 16V 0.8Ohm ESR capacitor would give a correct signature. and that is confusing me. The other day i wast testing a bulged capacitor with the tracker and the difference between a...
  19. HellasTechn

    Huntron Tracker 2000.

    At the time being i am more troubled with locating bad capacitors on a board without having to remove them first. Further more i would like an instrument that could reliably indicate a faulty capacitor even removed from the board. i have one of these cheap capacitor-ESR meters sold on e-bay...
  20. HellasTechn

    Huntron Tracker 2000.

    Thank you for all the helpful information. I have already bought a cheap step down transformer and begun playing with the tracker.So far i have tested several capacitors known good and known bad once and i have to say that it is hard to tell the difference between them.
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