Need rep.help for TV: "East-West-problem"

[danyat]

Hello,

i have a grundig tv set (29304) (schematic url is at the end) with an east-west-problem (i dont know if this is the technical name - at least in german it is known under this name) - this means the picture is smaller in the middle, than on the top or bottom.
It looks )_( instead of [_].

The width of the center seems also to depend on the brightnes of the displayed picture.

Can somebody help me, or at least give me tipps, where i should start searching.

The circuit diagramm can be found at: **broken link removed**

TIA
Daniel

 

[banjo]

I think your first clue is what voltage is at test point "+A", this is the main VCC supply for the horizontal stages. This voltage varies with the exact chassis you have. There is a table where you can find the exact voltage. (It is between about 140 and 155V.)
If "+A" is low then either your main power supply from the AC powerline is defective or you have a big load somewhere.

Get a good bright lamp, and with the set un-plugged do a very through visual inspection of both sides of the board. You are looking for overheated components on the top side and burnt traces and cold solder joints on the bottom. On the bottom pay attention to the pins of the transformers. These often do not solder well and break loose over time. Also look at any large coils. Make sure they are solder well.
Look at all the large electrolytic capacitors in the power supply and horizontal section. Look for capacitors that are a different color than the others, or are buldged out, or seem to have leaked their guts. (These are the capacitors in cylinderical cans that have polarity (+-) marks on their bodies.
Finally, what you are describing is a pin-cushion defect. Sometimes this is caused by a defective yoke. If this is the case, it is often not worth repairing because the part is glued onto the neck of the picture tube.