Prewar Marconi 707

[yagosaga]

Hi folks,

two weeks ago I get my first prewar tv set. It is a Marconiphone 707. The set was repaired in the 1990s. The bad Emiscope crt with broken filaments was replaced by a regunned 9" crt. Nearly all capacitors were replaced by new ones. The line output tube, KT63, was replaced by an EL36.

When I got it, there was no sound and only a small bright spot on the screen. The rectifier tube, U52, had broken filaments. I replaced it with a 5U4. Now the set displayed a bright raster (see first photo). AM sound, but no TV sound. I had to readjust the oscillator. After that, I got sound and video.

Due to the non-fitting crt which usually operates with more than 10 KV, focus is bad and width is not sufficient. The line oscillator was running with the half of the line frequency with double pictures on the screen (see the second and the third photo).

Meanwhile I have set it back to full line frequency, but with the result of a much smaller picture (see last photo). My next steps will be to replace the EL36 by the original KT63 and to replace the 9" crt by a 7" crt.

Kind regards,
Eckhard