Search results

  1. HellasTechn

    How do I test these transistors? (electronics noob here)

    This is IGBT i think. Correct me if im wrong but you can test them like a normal transistors (darlington pair) using B,C,E pins and B-D pins to test the base diode.
  2. HellasTechn

    Need help to find output of board

    The card with the LED is most probably a micro controller board. It kind of looks like a remote controlled garage door control assembly. The card with the opto's and transistors is a driver card for bigger loads .
  3. HellasTechn

    I cant measure voltage on 100 picofarad capacitors on multimeter

    I forgot that we where talking about pico farads.
  4. HellasTechn

    I cant measure voltage on 100 picofarad capacitors on multimeter

    Thats probably the best approach. Still you could do an ohms test with an analog multi meter. you should see the resistance rising as the capacitor is charging up. YOu will not be able to figure out it's capacitance value but it will give you an idea that is is actually storing something.
  5. HellasTechn

    I cant measure voltage on 100 picofarad capacitors on multimeter

    That is not what i ment. If you hook a cap in parallel with a power supply and measure the voltage across it (with the supply still on it) then you are mearly measuring the voltage that the supply is giving you not the voltage that the cap can hold.
  6. HellasTechn

    Help with capacitor question.

    Generally speaking, yes it does, if you have enough space on the pcb and housing. You will probably find them at your local electronics shop and on ebay or such sites.
  7. HellasTechn

    I cant measure voltage on 100 picofarad capacitors on multimeter

    Why do you need to measure the voltage of a charged capacitor? In practice the voltage will equal the supply voltage. At least for a certain time period. There are meters that can calculate capacitance, ESR and the voltage drop (in certain freq). There is no point in doing that. He will ony...
  8. HellasTechn

    Any info on these old chips ?

    Amazing. You found them all ! THANK YOU. Rhetorical question : Now what can one do with them ? P.S. I cant help wondering if i am just a poor "googler" or what ?
  9. HellasTechn

    Any info on these old chips ?

    Hello ! Iv'e got my hands on an old PCB haveing a number of IC's on it. For most of them i found the datasheets online but i have four that i can not find. Here is a picture of them : Markings are : a)Ti 527 b)Ti TL710MJ c)6330-1J d)7483N7720 Thank you :)
  10. HellasTechn

    LM1117 linear regulator.

    Yes that is also true but for the specific project i want to have a power supply as smooth as possible so i am not thinking to use a buck converter now.
  11. HellasTechn

    LM1117 linear regulator.

    I am going to check both the datasheets for their thermal characteristics but after readig the above i suspect the 7805 is betterfor larger input voltages.
  12. HellasTechn

    LM1117 linear regulator.

    Very interesting ! I will keep that in mind. Thanks ! In the end of the 2nd pdf it states that it is a good idea to test the actual board (with the chosen caps installed) under various loads and see how it performs. So as for my prev question 7805 for input voltages of 8V or above and 1117 for...
  13. HellasTechn

    LM1117 linear regulator.

    Yes that makes perfect sense. Now i keep thinking what are the real advantages of using an LM1117 over an LM7805 ? Is it only its small size and SMD package or anything else ? In my particular case i now use the 7805 with only two ceramic disc capacitors and a small heatsink. If i switch to the...
  14. HellasTechn

    LM1117 linear regulator.

    Thank you bertus. If i understand correctly for the TO-252 1 watt will pull its temp 45.1 deg above ambient, am i correct ?
  15. HellasTechn

    LM1117 linear regulator.

    Greetings dear forum members. Today i am considering a power supply for a microcontroller. In particular one that will implement an LM1117 regulator the TO-252 package. In the past i have used the 7805 regulator many times and i am pretty familiar with its cooling requirements but when it comes...
  16. HellasTechn

    Help recovering fdd with bad sectors LINUX or Windows

    To be honest i have abandoned the attempt due to lack of time. i just saved all i could and thats about it. besides the link that bertus gave us has all i wanted.
  17. HellasTechn

    Issues with micro usb connector on circuit board

    You can solder the new micro usb socket on the pcb. The far left and far right pads appear to be okay. There are two middle pads that came of the board. These pads are for D+ and D- lines. Now you have to solder wires on these two pins on the new micro usb jack and either scrape of the solder...
  18. HellasTechn

    RS422/485 and ground wire.

    In my DIY topology i have 4 rs422 devices where 1 is sender and 3 are receivers. Yesterday i took my DMM and tested the power supplies of my devices.All of them use switching power supplies. Surprisingly i dscovered that one of them had the negative lead connected directly to chasis ground with...
  19. HellasTechn

    Dell Harmon Kardon Hk395 pc speakers volume control

    In order for you to be able to use it's maximum volume range you will probably have to turn the pot all the way up (assuming it will work in that position) and then ontrol the bolume from your PC. That is not a recommended methid if you ask me because you may experience increased noise level...
  20. HellasTechn

    RS422/485 and ground wire.

    They do have the +5V and GND lines though. So when connecting a USB device with an other one we use the same common ground through the PSU.
Top