Wiring circuit

Showing posts with label troubleshooting. Show all posts

Thursday, September 4, 2014

TROUBLESHOOTING SANYO LCD 19R30 19 LCD TV

No raster_Sound normal, but no picture_ Picture normal, but no sound_Some source channel work abnormally.

No raster (screen is not lit), no picture, no sound

If detect NS01 (main chip) pin 169 is of high level, you may remove RS14, detect VS01 emitter if first output high level after power on, then output low level continuously. If not, the reset schema may have problem. First detect if NS01 (main chip) pin 44 waveform is sine wave, if not, check NS01 crystal oscillator schema. When checking periphery of NS01, NS02 and NS05, check relative component’s welding, then use oscilloscope to detect the joint resistor pin between NS01 and NS05. If the waveform is not regular square-wave, that means either NS01 or NS05 work abnormally and therefore cause address line and data line be in error. NS05 error probability is greater. In addition, if joint resistor between NS01 and NS05 is in error, it will also cause no raster, no picture and no sound.

CLICK ON THE PICTURES TO ZOOM IN

Sound is normal, but no picture. (Blue screen and OSD can be displayed.) Note: HDMI channel is excluded.

Sound OK, but no picture (only backlight lights up)

Picture normal, but no sound.

Some source channel work abnormally.

Note: To get normal HDMI picture, especially when connect to DVD player with HDCP information, it must be guaranteed that NV04 and NV05 (HDMI port DDC chip) writing is correct, and especially bus between NV04, NV05 and HDMI jack must be smooth and unhindered. Secondly HOTPLUG schema must be guaranteed (it is of high level at normal broadcast), otherwise the picture playback cannot be normal.

To get normal HDMI sound, especially when connect to DVD player with HDCP information, it must be guaranteed that NV04 and NV05 (HDMI

port DDC chip) writing is correct, and bus between NV04, NV05 and HDMI jack must be smooth and unhindered, otherwise the sound playback cannot go.

Troubleshooting STR IC Regulator Power Supply

A. Unable to start.

Can be caused by:

No start-up voltage supply Vcc or a voltage less than 16V
Electrolityc Capacitors supply voltage Vcc filter dry.

2. Led indicator blinking

If the supply voltage Vcc examined rocking. This is because the regulator of life and death because OVLO work., Die-protectionist regulators and auto start life over and over. If it is turned off Electrolityc Capacitors usually still keep the rest of the cargo.

Can be caused by:

Electrolityc Capacitors supply voltage Vcc filter on a pin-4 dry. Replace with a value equal to or slightly larger. - triger UVLO
input filter capacitor on pin-1 feed dry behind the declining value - triger OLP
Rectifier diode of the switching transformer is damaged (sometimes when examined with avo-meter looks like a still good)
cause the supply voltage Vcc drops of the switching transformer (UVLO)
Part damage or broken lines on the feedback circuit of the voltage regulator through B to photocoupler - triger OVP
Electrolityc Capacitors dry filter voltage B - triger OVP
One of the output voltage of the switching transformer secondaries there is a short (over load) - triger OLP
Soft start capacitor value decreases - triger OLP

3. Noise arising (noise)

Can be caused by:

Transformer windings slack.
If there are ceramic capacitors - can sometimes cause interference noise due to its characteristic piezoelectrik like crystal resonator. Replace with film capacitors.

4. When the st-by normal stress. But when the power is on the regulator directly off protectionism no voltage on the secondary this part. Electrolityc Capacitors are still storing charge.

Can be caused by:

Sensor OVP small value resistor on pin-2 to the ground so that the value of delayed triger to OLP or OCP.
Regulator IC is damaged

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Note: Be careful when the regulator is not working. Because of Electrolityc Capacitors may still have a charge when turned off.