View previous topic :: View next topic |
Author |
Message |
daa
Joined: 18 Jul 2007 Posts: 6 Location: Hastings
|
Posted: Wed Jul 18, 2007 4:34 pm Post subject: Distortion on TV picture |
|
|
The analogue image on my TV is perfect but when coming from my Daewoo SV-900 digital VCR the image will creep to one side (always to the left, in the middle) depending on movement in the image itself or a change in camera angle. It also happens to a lesser extent when coming via my PVR.
As current TVs do not have horizontal and vertical hold knobs anymore how do I correct this fault if possible and what causes this problem?
Any help appreciated. |
|
Back to top |
|
|
torbjorn
Joined: 07 Jun 2007 Posts: 370 Location: Sweden
|
Posted: Mon Jul 30, 2007 12:12 pm Post subject: |
|
|
Begin with trying alternatively CVBS (composite) and RGB signal from your digital sources and check if the you have the sync problem in both cases.
In some cases, TVs have badly designed input stages for the video signal which cause clipping of the sync pulses if the signal source has a DC offset that the TV manufacturer did not cater for. In order to assess a such problem properly, one must study the circuit diagram for those parts of the TV, measure the incoming video signal by oscilloscope and check DC offsets etc, and possibly make some kind of test hookup to change the DC offset of the signal.
I have once tried using a bench power supply connected in series with a 1 kohm 2 W resistor in parallell to the video signal, then it is easy to change the DC offset by adjusting the output voltage and polarity of the power supply.
According to official standards for video signals, the black level should be at 0 V, sync tips at approximately -0,3 V and white level at +0,7 V. But in order to save a negative supply voltage, much consumer electronics have sync tips at 0 V, black level +0,3 V and white level +1,0 V. In really weird cases, several volts of positive offset have been found. |
|
Back to top |
|
|
|
|
|
You can post new topics in this forum You can reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum
|
eServiceInfo on FB -
Service Manuals Free Download -
Service Diagrams
Free TV Schematics Download -
HARDW.net -
Pinout Master -
Jabse Service Manual Search -
Jabse.InK -
onTap.bg
SnimkiOt.com -
Poblizo.com : пътешествия
Latest Service Manuals :
42LP360H, 361H LG • VS425EDG Akai • 13255-91064 2K Memory Module Aug76 HP • 54-04 Philips • hfe ta-2026 service en ONKYO • Lead100 Vox • sony cdp-970 sm . Various • hfe panasonic sa-hr45e eg service en pan • XR-C5100 Sony • N2750-97002 N2750 1 2A Differential Prob •
|