Audio Systems: TV Hifi & Mains Hum, line level signal, phono inputs

Question
I'm pretty sure that when you use the term "twin-phono audio out", you're referring to the type of output jack (tho' I thought I understood both the UK and US used the same RCA interconnect jack), a 1/4" phono jack and *not* PHONO inputs on the Quad. Of course PHONO inputs can only be used with turntables because of the circuitry boost required to compensate for cartridge output, which is very low.
Kevin

Kevin
RCA jack plugs are commonly referred to as phono plugs in the UK. The Quad uses 5 pin DIN plugs for input (truly old tech). The TV has twin RCA outputs which are going into the inputs on the amp called 'Radio 1', 'Radio 2', and 'Tape'. These can handle a line-level signal from other sources (such as CD) without difficulty.
I have a more modern hifi system, which I dragged into the room and connected up. It can take the input from the TV without hum.
Thanks for your reply.
Mick


Answer
Dear Mick,

Thanks for the clarifications.

If the hum occurs when you use the Quad versus another amplifier, then it would seem that the problem's with the Quad. I would have the unit bench tested by a qualified repair technician to see if the hum can be isolated. My guess is that the amp's transformer isn't sufficiently grounded, the chief cause of main hum. But I'm stumped as to why that would occur with the TV and not other inputs.

You might want to pose this question to allexpert Cleggsan, who is far better versed in electrical theory than I.

Kindest regards,

Kevin