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Heatercathodeshort · 24th Feb 2018, 10:27 am

That looks great!

Line drift from cold is a very common symptom with self oscillating line output stages.
Valve spread as the PL38 warms up and changes in the inductance of the line output transformer as the windings reach a stable temperature are the reasons for the line drift.

The line hold control being an inductor is also responsible. It was not unusual to allow a 15min warm up time. Receivers were just switched on 15 mins before the programme commenced and were then stable throughout the broadcast without having to fiddle with the controls.

The LV30 series were very reliable and introduced the first of the Mullard/Philips 'World Series' B9A valves. Regards, John.

24th Feb 2018, 10:27 am	#14
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Restoration of my Pye LV30 That looks great! Line drift from cold is a very common symptom with self oscillating line output stages. Valve spread as the PL38 warms up and changes in the inductance of the line output transformer as the windings reach a stable temperature are the reasons for the line drift. The line hold control being an inductor is also responsible. It was not unusual to allow a 15min warm up time. Receivers were just switched on 15 mins before the programme commenced and were then stable throughout the broadcast without having to fiddle with the controls. The LV30 series were very reliable and introduced the first of the Mullard/Philips 'World Series' B9A valves. Regards, John.