Turret v mechanical push button TV tuners.
Richardcoulter
Posts: 30,314 Forum Member
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A different thread has got me wondering how the different systems worked.
I'm assuming that a turret just moved along the frequencies rather like a radio tuner, but how did the four (or more) pre set push buttons make the tuning connection?
To say they were mechanical, I never ever had any problems with them (even when as a child I used to play about with them). I found that having all four of them sticking out didn't produce anything but white noise, that you could press two in at once, that you could retune them by twisting the push button round and that making the button come back out slowly after a channel change often made it skim through one or two channels on the way back out 😈😀
All good fun abusing a television set as a kid, but how did it all work?
Convenience aside, which was the best tuner from a technical point of view?
Did they ever make any UHF or colour TV's with a turret tuner, or was this considered old fashioned by the time this technology was introduced?
I'm assuming that a turret just moved along the frequencies rather like a radio tuner, but how did the four (or more) pre set push buttons make the tuning connection?
To say they were mechanical, I never ever had any problems with them (even when as a child I used to play about with them). I found that having all four of them sticking out didn't produce anything but white noise, that you could press two in at once, that you could retune them by twisting the push button round and that making the button come back out slowly after a channel change often made it skim through one or two channels on the way back out 😈😀
All good fun abusing a television set as a kid, but how did it all work?
Convenience aside, which was the best tuner from a technical point of view?
Did they ever make any UHF or colour TV's with a turret tuner, or was this considered old fashioned by the time this technology was introduced?
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The 625 line set ended up with a faulty tuner which caused the picture to drift out you would see a black line at the side of the picture this was after about 5 years of use
All early UHF tuners used a variable capacitor (several sections for the RF and local oscillator) and this could be turned via a continuously variable knob (usually geared down to ease tuning) or a four button preset mechanism which simply pushed the capacitor to a known position for each channel.
Later tuners used electronic tuning (varicap diodes) which replaced the mechanical arrangements. Tuning was then by a simple rotary knob (which turned a carbon pot) or by a four or six-way push-button switch which selected pre-set voltages from four or six customer-settable miniature pots, often hidden behind a flap.
Later systems used digital methods to store the tuning voltage for each channel.
Happy days.....
This used a 'permibility' tuner which had brass or ferrite slugs sliding inside paxoline tubes on which the various tuning coils were wound. The rotary channel change control had steps which moved the slugs in or out to the required position for a particular channel. A slide switch operated to change from Band 1 to Band 3.
Quite reliable as it didn't have so many critical contacts as the biscuit type tuner.
My grandmother had one like that, two buttons were band one and labeled BBC the other two were band three and labeled ITV. Most sets had a turret tuner, some rental sets only had two of the coil biscuits fitted, it you turned the knob the wrong way it bent all the tuner contacts, I did that on my uncle's set and it was stuck on ITV until the man came to fix it. The solution was to move the biscuits to adjacent positions and then just go back and forth between them.
Yes, I recall our DER rental set, the 4 UHF tuning buttons having ferrite tuning slugs in them, if you pushed one of them in further than its settling point, you'd go off tune, enough in some situations to see another channel
Yes I do remember those. "Turn the telly over lad" thunk, thunk, thunk!:)