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  1. HellasTechn

    Serial communication problem.

    Hello everyone. I am working on a project that requires computer serial RS232 communication and i am getting some weird behavior on it. I have a source of rs232 serial data (idle low -15V) that feeds data to a PC and at the same time (in parallel) to a card that reads TTL rs232 (+5V idling at...
  2. HellasTechn

    YAMAHA AST-C10 no audio

    Hello everyone and have a nice day. This time i am working on a Hamaha ast-c10. It will power on but the output relay will not click and no audio is heared from the output. I have found a few bad capacitors around the power amplifier chip and replaced them but still not working. I can not scope...
  3. HellasTechn

    CCFL lamp tester

    Hi there friends, I am thinking to buy a ccfl lamp tester, specifically this one : http://www.ebay.com/itm/CCFL-Tester-Repair-LCD-TV-Laptop-Display-Backlight-Lamp-Test-Car-Motor-Angel-Eye-/281025374369?hash=item416e6ae8a1:g:WPMAAOxycSdR0IV7 I have a question though, how can i tell which side...
  4. HellasTechn

    Help with A123 transistor.

    Good day to all ! I need information on a transistor marked A123 (TO-92). Is it PNP or NPN ? it's pin arrangement or even better if anyone knows an equivalent. It was mounted on the control board of a refrigerator. i have no other info on that. Thank you all ! P.S. I found it on e-bay but no...
  5. HellasTechn

    TV Samsung LE32B450C4W bad PSU.

    Hello friends, I am looking at this Samsung LE32B450C4W television that would blow the PSU main fuse when connected to MAINS. I found the bridge rectifier Shorted and a blown mosfet (QP802s K10A60) i replaced both (actually the K10A60 with a K15A60) and the mainboard comes on. I hear the...
  6. HellasTechn

    220V solder iron under 110V

    Hi ! I have this silly quiestion. Most ships i work on have 110V-120V mains power (two supply lines of 60 volts 180 deg out of phase). I also have a solder iron that works on 220V and gives 40W. This solder iron is consisted of the heating element and a 1N4007 diode in series. If i remove the...
  7. HellasTechn

    SMD components question.

    Good day everyone ! Lately i had many problems with smd devices, my main issue is to identify them so i can measure them. To be more specific, all PCB's use theese SOT-23 smd devices. I have come across a large number of markings on them and honestly i find it very hard to identify them. Today...
  8. HellasTechn

    Very Old Components I Can Not Identify.

    Happy New Year everyone ! After digging into a box filled with old stuff i came across many chips inside their original packing that i have no idea what they are or what they do. I have googled their markings and came up empty. I have even looked them up on e-bay but no luck there either. They...
  9. HellasTechn

    THANK YOU ALL

    Good day ! Triggered by an incident that took place in our forum a few days ago, i want to say a big thank you to Administrators - Moderators and to most of the members of this forum for being so helpfull and kind ! To me that really proves that in here we do respeact each other ! THANK YOU...
  10. HellasTechn

    Capacitor question

    Hello friends ! I would like to ask about this capacitor. I have seen such in old telephone sets and in switching PSU's. What kind of caps are they and what are they mainly used for (audio applications?) ? Also how can we read it's value ? Is it the same way we read ceramics ? Thank you !
  11. HellasTechn

    Marine Radio Transceiver repair.

    Good day! My father had this old Marine radio transceiver. The brand is : Lear Operations Research & Development Corp. and the model is XT700. I guess it dates back to the 80's. when power is connected it turns on, display is ok, channel selector works but squelch, volume dont work. Also it...
  12. HellasTechn

    My old toy radio transceiver

    I was looking at some stuff in the house where i grew up and found a bag with some of my most favrite toys. They where two Fisherprice military style radio tranceivers (3070) that me and my brother loved to play with. http://www.thisoldtoy.com/l_fp_set/toy-pages/3000s/3070-sonicrangers.html...
  13. HellasTechn

    Floating pins on Microcontroller

    Hello friends. I have this question for you. I am building microcontroller project with a Picaxe and i want to be able to reprogram it without rmoving it from the PCB. so i was thinking that ok Serin pin uses the 10K resistor as pulldown when nothing is being downloaded to it but what about...
  14. HellasTechn

    USB to RS232 adapter

    Hello there friends ! I have this issue lately with RS232 and modern laptops that do not have a such port. Because i use Picaxe microcontrollers and other devices like GPS receivers i need a serial port that can transmit and receive rs232 data. I bought this cheap chineese cable...
  15. HellasTechn

    Advice on LCD display for Picaxe project.

    Hello friends and have a nice day, I want to practice interfacing picaxe with LCD dispay i have never done that before and i guess it will not be easy for me. Can anyone suggest me what display i should use ? Picaxe manual has info on 16x2 AXE033 SERIAL/I2C LCD...
  16. HellasTechn

    What kind of capacitor is this ?

    I see theese capacitors in many devices, specially in the high voltage section. They have small capacitance value and high voltage rating. What kind of caps are they and what are they made of ? Thanks.
  17. HellasTechn

    Switch question.

    Hello ! I used to have soem switches like this one : http://www.ebay.com/itm/1pc-Momentary-Switch-3-Feet-3-Pin-2A-5A-On-On-3-Pins-Miniature-Toggle-Switch-/351668104001?hash=item51e10d6b41:g:qh0AAOSwWTRW15zD Only they had an internal spring that would force the lever to go back to its initial...
  18. HellasTechn

    Bad Capacitor !

    Good day to all ! This is really funny. I had a digital terrestrial mpeg4 decoder that was not working so i opened it to see what was wrong and i came across this ! I have seen bulged and leaking capacitors but this ! when i poped the cover off the capacitors cell fell off.
  19. HellasTechn

    LM318N comparator circuit

    Hello friends. A friend of mine has this homework and needs help but have no internet acces so i post it on his behalf. This circuit with the lm318N must trigger the buzzer when input voltage reaches 13 Volt. Here is the circuit. The transistor is a BD 649. He used a variable DC supply...
  20. HellasTechn

    JVC AX-R551X PROBLEM

    Hello ! i am back with some more trouble :) I have a JVC AX-R551X on my bench. When it came to me all the power transistors where burned (2sa1264 and s2c1381) as well as a number of other transistors and diodes. I replaced them all with new and now the amplifier will power on, all controls in...
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