Sanyo CE28WN5-B

[stevemb]

The picture has shrunk in width, the edges arre jeagged and with no aerial connected the intermittent blue screen has flyback lines on it. Help !

[meesa]

If it has a philips/lg crt...thats more than likely causing your flyback lines, probably internal arc causing scan problem too.

[torbjorn]

Check that the supply voltage to the line output stage is correct. If too low, all voltages to the CRT will also be too low, which might cause the automatic bias circuitry to drive the video output amplifiers into clipping, causing the flyback lines.

Some of those sets have an extra blanking circuit with a number of transistors and diodes connected to the RGB lines between the PAL decoder IC and the video outputs, however i have not seen that circuit in any schematic diagram. It has caused some strange symptoms, but it seems that the sets are working normally if that extra blanking is disabled, for example by shorting B-E of one of the transistors.

When adjusting the screen voltage of those sets, STRICTLY follow the procedure of the service manual. You will NOT get correct results by just turning the pot while watching the picture until the flyback lines disappear, as you can do on most other sets.