B&K 1077B Tough Dog Problem

[Tom9589]

I finally got my B&K 1077B where I want it except for one pesky thing. I have vertical deflection instability. The amount of vertical deflection jumps up and down. It gets better as it warms up, but never goes completely away.

Here is what have done so far:

1. Replaced all the electrolytics in the vertical and power supply sections (including B Boost capacitors)
2. Replaced all non-electronic capacitors in the vertical section.
3. Replaced all out of tolerance resistors in the vertical section.
4. Cleaned all the tube and tube socket pins with Deoxit.
5. Tried a NOS tube in the vertical circuit.
6. Re-flowed all of the PCB solder joints in the vertical circuit.

Waveforms:

1. Vertical plate and grid waveforms look steady with no bouncing around.
2. Vertical cathode waveform bounces around in sync with the raster bouncing on the TV.

There is a new capacitor in the cathode circuit of the vertical output stage and I have tried a fixed resistor in place of the vertical linearity control. No change.

Does anyone know if vertical output transformers are a problem in these units? At one time, I thought I could repeat the problem with freeze spray.