UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Cretinous idea

G6Tanuki · 12th Oct 2019, 8:16 pm

The TV "combine brightness and on/off to avoid spot-burn" thing seems like a good idea, but I'm wondering - once we got tellies with push-button on/off switches in the 60s and then the 1970s arrived and TVs had remote-controls with separate brightness and on/off functions, was there ever any attempt at 'spot-blanking' applied ?

I certainly don't remember seeing a central switch-off-spot on any push-button-on/off or remote-controlled TV when switching off using the remote.

Was the whole 'switch-off-spot' thing a bit of a red-herring? I can understand it being an issue with old-fashioned power-supplies using a mains-transformer with an EHT winding and significant smoothing-capacitance so there was a bit of stored energy, but surely not an issue with flyback-derived EHT and 'coated' tubes with only a few hundred pF of capacitance to store EHT-energy?

12th Oct 2019, 8:16 pm	#26
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,995	Re: Cretinous idea - The combined volume pot and mains SW. The TV "combine brightness and on/off to avoid spot-burn" thing seems like a good idea, but I'm wondering - once we got tellies with push-button on/off switches in the 60s and then the 1970s arrived and TVs had remote-controls with separate brightness and on/off functions, was there ever any attempt at 'spot-blanking' applied ? I certainly don't remember seeing a central switch-off-spot on any push-button-on/off or remote-controlled TV when switching off using the remote. Was the whole 'switch-off-spot' thing a bit of a red-herring? I can understand it being an issue with old-fashioned power-supplies using a mains-transformer with an EHT winding and significant smoothing-capacitance so there was a bit of stored energy, but surely not an issue with flyback-derived EHT and 'coated' tubes with only a few hundred pF of capacitance to store EHT-energy?