On many of the old antenna-input only mains powered TVs, the entire 0V rail / chassis is at 1/2 of the mains input voltage (therefore at 120 volts in 240V countries) due to the design of the power supply. The giveaway for these is that the antenna socket typically has an RF isolating transformer built into it, otherwise the outer body of the antenna plug and the entire antenna system would also be at half mains voltage.michele.x wrote:You could also use a stand alone TV modulator. These are normally used to inject the signal from a satellite receiver and see the single channel on all the tv sets of the home.JeremyF wrote: I'm sure you know, but for anyone reading this...if you have a super-old / super-basic TV you can plug a VCR with additional composite inputs into the coaxial/antenna connector and then plug the RPi into one of the VCR's inputs. just to make sure no one gets confused
Not sure if my clarification was necessary, but I feel helpful.
The cheaper ones tend to cost at least 30 €. The DIY route is a bit cheaper, but you still need to encase them in a fully shielded metal box so the price is still in the 30 € range.
Beware that on some old transistor TV sets, even in B/W it's possible to bypass the RF section, cutting some jumpers and downgrade them as monitors: the circuit bord was designed at dual use. Of course to do this you must be a trained tv technician and have the schematics and the pcb layout of the tv set.
I used to work in a radio/TV repair workshop - I can recall a few cases where people were complaining they were getting fairly serious electric shocks when plugging their antenna in - usually, the original isolated antenna socket had failed at some point and been replaced with a simple non-isolated socket.
None of this applies to any TV with existing video input connectors such as composite, component, S-video or Scart. In all of these cases, the power supply has been designed so that the chassis is completely separated from the mains input supply.