Peto Scott TV169 Restoration.

[Murphyv310]

Hi David.
Similar to the Peto Scott but with the addition of an ECL80 in the Ferranti. The EB91 in the Peto Scott is biased off under normal conditions, if the scan from either line or frame reduces the brightness level drops, not ideal as width and height effects brightness, any less than half width and the picture dissapears, it's less noticeable on frame though.
On this set the cathode of the CRT is modulated, unusual for a projection set.

[Geordie McBoyne]

Hi Trevor,
            here's another tube protection circuit.  The White-Ibbotson Mark 1 and 2 projection receivers employ a single EB91 as the fail safe protection device.
In this circuit it would appear the waveform on the line scanning coils provides after rectification by the right side section of V14 the positive voltage supply for the brightness control VR9.
In the event of frame timebase failure the left side section of V14 provides the protection. This part of the circuit needs further study as to ascertain how it works in the brightness control.

Negative going video supplied to the cathode of the CRT.

Geordie McBoyne.

[Jac Janssen]

On this set the cathode of the CRT is modulated, unusual for a projection set.

Hi Trevor,

For example the Philips 600A, 704A, 1800A, TX701A also have the video to the cathode.

Jac

[Murphyv310]

Thanks Jac.
I think both myself and David were under the impression that in the main grid modulation was more widely used.

[LENINGRAD T2]

Hi,
I found information on the web that TV Peto Scott 169 was presented on the radio exhibition in 1951. Perhaps the designers were in a hurry to present a TV set that had some technical flaws. I also believe it disappeared very quickly from sale since the original wiring diagram cannot be found in the available publications. But I did find a twin named Peto Scott 169. He's probably in the Birmingham Museum. I enclose a link on this topic. Maybe the Museum has documentation for this TV?

Adam

https://twitter.com/tommymarlow/status/1...92/photo/1