[Argus25]

If there is at least part of a scanning raster on the screen to see (which you have) its appearance can tell you an awful lot about the fault.

For starters the raster width is about right, so this means that the HT supply to the horizontal osc and H output stage is roughly correct and the H osc frequency roughly correct and because you have reasonable CRT beam current, the EHT is working and the focus is not way off, so the CRT is probably ok or at least good enough.

You won't be able to assess the signal process circuits and audio/video system until you feed it with a known good test signal.

The main fault that is evident is severely impaired vertical linearity and loss of vertical scanning height.

Since the vertical scan starts at the top, the vertical yoke coils are supposed to have a linearly increasing current, with the peak current occurring at the bottom of the raster, prior to V flyback. This is why, when many vertical scan faults appear, there is loss of height and compression of the scanned lines toward the bottom of the raster as the drive circuit fails to supply the required peak scanning current.

So, the CRT raster you are looking at (and the beam deflection you are seeing) is in a way like an oscilloscope recording of the yoke currents.

There are multiple reasons why this could happen in an old set, I will just list a few:

1) Distorted drive waveform to the vertical output valve (waxies & resistors defective)
2) DC conditions incorrect (cathode and or screen resistor on vertical output valve faulty or faulty screen bypass if there is one)
3) Vertical output valve cathode bypass electrolytic faulty (if there is one)
4) High value resistors in linearity circuit/feedback components, leaky waxies.
5) Vertical output valve itself defective and low on emission.
6) Reduced HT to vertical output stage, of faulty electrolytics allowing the supply voltage to drop as the yoke current increases.

So in summary the vertical output valve's condition, its DC conditions and the shape of the drive waveform presented to it and the qulality of the power supply can all affect the vertical scan amplitude & linearity.

So in this sort of case, before doing anything you will get further ahead if you renew all the capacitors in the vertical oscillator and output stage (where they are waxies & any electrolytics) and check every resistor for the correct value. Then check the HT supply to the stages and replace the V output valve if that does not fix it. It is fairly easy to see with a scope too, if the vertical drive waveform is abnormal, or the problem is in the output stage itself.

Vertical output stages in valve sets are a lot like audio amplifiers in their design, though there are usually more feedback components (resistors & capacitors) around the stage to help attain good scanning linearity.

PS: if it is a hot chassis set (neutral to chassis) its best to power it by an isolating transformer and earth the chassis before connecting other earthed apparatus like a scope to it.

Also, it is obvious from the remarks above, this is the reason why some TV restorers replace all the waxies and all the electrolytics in a set, prior to powering it, as it significantly reduces the number of faults to track down and drastically improves the reliability and could be regarded as the basic initial restoration.