Black and white TV - UK Vintage Radio Repair and Restoration Discussion Forum

Stylo N M · 5th Nov 2013, 9:29 pm

Hi all,
In the 1970s we had a Stella valve TV on legs with a push button tuner, for most of its life which was about 18 years, it suffered from an annoying humming noise, the humming noise could occasionaly be knocked out by switching the set off, then counting to 3 and sharply switching back on again. It wasn't a fault according to our electrical service dealer, so what was it? We have a hospital a quarter of a mile away, someone once said that may have been the cause. It also used to pick up Radio Prague on occasions, so what was the mystery humming noise? Any ideas?

Thanks, Paul.

Nicklyons2 · 7th Nov 2013, 12:42 pm

Well there could be many causes but here are a couple. The humming could be a faulty sound o/p valve with intermittent heater cathode leakage; the insulation between heater & cathode is failing and the a.c. heater voltage appears across the cathode circuit - turning off, the filament and cathode cool a little, contract and the insulation 'heals' slightly etc.

Picking up Radio Prague; well if it was in their shortwave services it may have been trouble in the IF or intercarrier departments, if their MW service it was probably more likely to be screening/earthing problems in the audio stage.

jamesperrett · 7th Nov 2013, 2:21 pm

I'd guess that the tuning had drifted slightly and the video signal was breaking through into the sound. I seem to remember this happening on our old Bush TV as it warmed up and the solution (after a number of service calls that didn't seem to fix it) was to simply adjust the tuning a little once it had warmed up.

5th Nov 2013, 9:29 pm	#1
Stylo N M Heptode Join Date: Jul 2012 Location: Derby DE1, Derbyshire, UK. Posts: 626	Black and white TV Hi all, In the 1970s we had a Stella valve TV on legs with a push button tuner, for most of its life which was about 18 years, it suffered from an annoying humming noise, the humming noise could occasionaly be knocked out by switching the set off, then counting to 3 and sharply switching back on again. It wasn't a fault according to our electrical service dealer, so what was it? We have a hospital a quarter of a mile away, someone once said that may have been the cause. It also used to pick up Radio Prague on occasions, so what was the mystery humming noise? Any ideas? Thanks, Paul.

7th Nov 2013, 12:42 pm	#2
Nicklyons2 Octode Join Date: Jan 2013 Location: Barnsley, South Yorkshire, UK. Posts: 1,517	Re: Black and white T.V Well there could be many causes but here are a couple. The humming could be a faulty sound o/p valve with intermittent heater cathode leakage; the insulation between heater & cathode is failing and the a.c. heater voltage appears across the cathode circuit - turning off, the filament and cathode cool a little, contract and the insulation 'heals' slightly etc. Picking up Radio Prague; well if it was in their shortwave services it may have been trouble in the IF or intercarrier departments, if their MW service it was probably more likely to be screening/earthing problems in the audio stage.

7th Nov 2013, 2:21 pm	#3
jamesperrett Octode Join Date: May 2007 Location: Liss, Hampshire, UK. Posts: 1,873	Re: Black and white TV I'd guess that the tuning had drifted slightly and the video signal was breaking through into the sound. I seem to remember this happening on our old Bush TV as it warmed up and the solution (after a number of service calls that didn't seem to fix it) was to simply adjust the tuning a little once it had warmed up.