Bush CTV184S: Picture Overscans

Symptom

The picture overscans by about 1¾” all around and is also dull. Suspecting that the oversize raster was due to low e.h.t. I replaced the tripler but this did not provide any improvement. The width tapping on the line output transformer was then set to minimum but the picture still remained oversized.

Solution

We are fairly sure you will find the 560Ω resistor 6R6 in the line output stage either open-circuit or otherwise damaged (this resistor is part of the network used to “balance” the two output transistors). It is usually damaged as a result of one of the associated capacitors 6C5 or 6C6 ( both 4700pF) being faulty: both should be replaced. The fault could be due to one of the line output transistors but this is less likely