Saturday, September 10, 2011

Akira Television 21 Inch dead

Roger: sir good day,,,,now I’m repairing a 21 inch,tv,akira,,,,the power regulator ic is down,,,so i replace,,,,there is also a ceramic disc cap rated 222k is burnt already at secondary side, beside output diode, so i replace,,,by the way the fuse have burnt also,,,,so i power the set using light bulb,,,when i plug i noticed the front led not lighted,,,,, what the area I’m going to check sir,,,maybe the micro not power also,bcos,,no 5volts,,,,, by the way this tv is using power ic,,,str g6653,,,even there is no 5volts ,I try to sw.on the set,,and i can do voltage testing,,,the main cap is 300v,,,pin 1 of ic is 300v also,,,,pin4 is about 14to 16v,,,,pls,advise me sir,,thanks,,roger

Humphrey: Any voltage on the secondary side of the power supply?

Roger: sir, good day,,,i continue checking at primary side, I bump to a resistor rated .15 ohms,,,its reads 18k ohms,,,so i check the link of this low ohms resistor,,,it connected to pin 2 of str g6653,,,it is a current sense resistor,,,that turn to high ohms,,,i think this is cause why the power supply and also front led not functioning,,,,,am i correct sir?,,,now im preparing to install a new low ohms resistor,,rated 0.47ohms,,,,,because    0.15-ohms is not available,,,,maybe this tv is start working,,,,after i replace total of 5 components,,,,,,by the way sir thanks,,,,,,i let you know ,after i fix this tv,,,,god bless,,,roger

Humphrey: 0.47 ohms is still quite high for current sense resistor...use three 0.47 ohms resistors connected in parallel to get 0.16 ohms for this circuit.

 Roger: ok,sir ill do that your good advise,,,,i will make 3 ,,,,,,,0.47ohms resistor in parallel,,,,thanks

Roger: sir good day,,,,after i replace a e-caps at the vcc rail of str g6653,,,when i sw.on the front led has come on now,,,,but i notice the light bulb is having intense light,,,,so i check the voltage at the secondary diodes,,,all are ok,,,but the B-positive is low,,,i disconnect the degauss coil,,,,check again the voltage at B-positive its reads 112v,,,so i confirm the posistor is already short,,,,Because  i check the degauss coil is ok,,,,now,,,all the voltage output at secondary is present,,,,but the tv does not sw.on,,,,,the front led is ok also,,,,,the micro is already powered,,,,but why the tv cant sw.on ?   so i check the condition of fbt,,,primary winding is ok,,,,i powered again the set and check the fbt secondary voltages,,,the 185v reads only 112v,,,,,,the screen voltages reads 3.2v,,,,,the other fbt output no readout,,,,,so why this happen sir think the fbt is already gone also sir? Even though the primary winding of fbt is ok? You know sir? I learn a lot in this trouble-shooting,,,pls.advise me sir,,thanks,,roger

Humphrey: I don’t think the fly back has a problem, I suspect the horizontal drive circuit, read your book chap 10 for more details on testing and troubleshooting this circuit.
The Voltage of 112volts at the output of the FBT is same as the 112volts b+ voltage because the fly back is not switching. So this leads us to suspect a problem with the drive circuit. For example any voltage at the collector of the drive transistor? How much?
Check that and come back to me please.

Roger: sir good day,,,,,yes is true that the output voltages the same,,,,,,112v,,,,now my mind is thinking so much,,,,I  have read again the book at chapter 10,,,,,i think my assumption is correct,,,to double check the horizontal drive circuit,,,,,,so i confirm to you sir about your advise,,,,,,sir you know you’re a nice guru for me,,,,,so i study hard for this field,,,,,especially CRT TV repair,,,,,big thanks for your advise sir,,,,,i let you what the progress of repair
Roger: sir good day,,, I check the horizontal drive circuit,,,,i power on the tv,,and test the voltage at collector of h-drive transistor it reads 112v,i trace the line is coming from the b-positive line,,,pass the two 10k resistor in parallel,,,,i check the pulses at the base ,,i find dry joints,,,,so i re-solder the area of h-drive and the pulses is ok,,, ,,,,now the set is totally power on,,,,sir you know I have so much learn about your advises for me,,,,i have so many things in trouble shooting that i have learn,,,,dos and don't,,,,procedures,,,the principles that I learn in your book is giving me a inspiration to continue learning this field,,,now my confidence is simply increasing,,,,,b-cous of your support sir,,,,


    i recommend you that when you are going to fix a TV or monitor older than five years first of all look for cold sloder points and then start to repair the TV otherwise the tv with cold solder points give you very strange symptoms that does not lead you to any where . some where in circuite you have voltages some where not and you can not diagnosis the real problem

  2. Very good info Mr.Beh, God bless u

    Regards Humphrey