REPAIRING AND NOT THROWING AWAY

REPAIRING AND NOT THROWING AWAY

Richtige Fernseher haben Röhren!

Richtige Fernseher haben Röhren!

In Brief: On this site you will find pictures and technical information about Service Modes, Circuit Diagrams, Firmware Update procedure, Disassemble procedure, Universal remote control set-up codes, Troubleshooting and more....

If you go into the profession, you will obtain or have access to a variety of tech tips databases HERE IT IS Master Electronics Repair !.

These are an excellent investment where the saying: 'time-is-money' rules. However, to learn, you need to develop a general troubleshooting approach - a logical, methodical, method of narrowing down the problem. A tech tip database might suggest: 'Replace C536' for a particular symptom. This is good advice for a specific problem on one model. However, what you really want to understand is why C536 was the cause and how to pinpoint the culprit in general even if you don't have a service manual or schematic and your tech tip database doesn't have an entry for your sick TV or VCR.

While schematics are nice, you won't always have them or be able to justify the purchase for a one-of repair. Therefore, in many cases, some reverse engineering will be necessary. The time will be well spent since even if you don't see another instance of the same model in your entire lifetime, you will have learned something in the process that can be applied to other equipment problems.
As always, when you get stuck, checking out a tech-tips database may quickly identify your problem and solution.In that case, you can greatly simplify your troubleshooting or at least confirm a diagnosis before ordering parts.

Happy repairing!
Today, the West is headed for the abyss. For the ultimate fate of our disposable society is for that society itself to be disposed of. And this will happen sooner, rather than later.

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..............The bitterness of poor quality is remembered long after the sweetness of todays funny gadgets low price has faded from memory........ . . . . . .....
Don't forget the past, the end of the world is upon us! Pretty soon it will all turn to dust!

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Tuesday 26 February 2019

SONY TRINITRON KV-1404 [NO SOUND: PICTURE OK]

  SONY TRINITRON KV-1404 [NO SOUND: PICTURE OK]


Before proceed to repair, note whether the sound mute function is On.  If ON, make it OFF.  If this setting is alright, check the voice coil of the speaker with a multimeter.  If speaker also has found good then proceed.

  •      Check all the solder terminals [9 of them] of the audio output IC (IC251_ TDA 2007). It is best to resolder all these solder terminals of thie IC, by applying a little more solder, becuse some loose solder points are very difficult to detect, as they might be microscopic to normal vision.
  •  If all of above are found OK, check the supply voltage comes to this IC.  Its main supply voltage is given to its pin (8).  14VDC should be present at this pin.  This voltages comes from SMPS power supply section, through a resistor [protection resistor]. [R613 - One Ohm].  Check this resistor for continuity. If found open, make sure that there is some short circuit with the circuit related to audio output section.
  •      Check (C251 - 1000Mfd 25V) for short.  It is best to measure the voltage between pin number (8) of the audio output IC to main ground.  In most cases, if the measure resistance is very low; say lower than 15Ohms or so, the audio output IC is likely to be shorted.  Resolder out the audio ouput IC from circuit, and measure this resistance.  Still found low, repalce [C251-100MFD 25V).  It is shorted.
  •      If the voltage at pin (8) of audio output is found OK, and thee is no output from the speaker, check the voltage at pin (9) [audio output].  It should be about 6.8VDC.  If this voltage is found abnormal [approximately equal to the supply voltage - 14VDC of found to be zero volt]; Without any doubt, repalce the audio output IC.  It has damaged.
     If all these voltages are found Ok, and still there is no audio output, touch pin number (1) of this IC with the blade of screw driver.  A hum sound should be there from speaker.  If there is this hum sound, and still you do not sound, the video IF section should be looked into.
In this set, sound processing section is inside the video IF unt [IF201 - IFB 389HS].  Check the voltage at teminal (8) of this unit, (audio out).  This voltage should be about [3.6VDC].  This is the audio signal output pin. Electronic volume control is used here.  The intensity of audio signal appear at pin (8) will depend upon the applied voltage at terminal (70 of this unit.  Check the voltage at this point.  It should vary, as we increse the volume of the set, either by its front panel of remote volume control buttons.
     This voltage comes from pin number (2) of main system control IC [IC 002 - PCA 84C640P-016].   Being picture is OK, sound must be there, as video IF signal out from the video output will have audio signal with it.  Because, audio signal is being modulated with video IF signals. The main function of audio processing section is to seperate and to pr-amplify these signals to sufficiant level to drive the audio output IC.
     The voltage at pin number [2] of the system control IC, stated above should vary according to the level of volume we set with panel controls. So if there is no voltage deveation present at termianl (7) of video IF unit, come to this check point at pin number (2) of main system control IC.  If voltage varies here with adjusting the controls, and not appear this difference at terminal (7) of VIF module, check [R093 -2K2, R030-3K3, R091 - 1K, C017 - 10MFD 63V and R011 - 100K, Zener diode D200 - 6.2V Zener diode, R 211 - 10K].  Check the Zener diode D200 for short].  Check the assicated components connected to termianl (7), if any.
     If all are Ok, and still there is no votage variation at pin (2) of main system control IC, it is defective, and should be repalced. If there is voltage variation at pin (20 of system control and terminal (7) of VIF module, and still there is no sound output, make sure that the video processing section inside the VIF unit is faulty.  There is no repair to this unit.  It should be replaced with same number.
Posted By: FRANK at 06:05
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