Mixed technologies radio.

[Murphyv310]

I've a thought.
How about a mixed technologies radio?
Rod pentode front end, RF stage and frequency changer, TA7642 as an IF amp and TDA2822 as audio amplifier?

[ppppenguin]

In the transition period from valves to transistors some car radios were mixed technology. Valve front end with OC16 or similar for audio output.

TVs transitioned slowly from valves to transistors. Did any TV use both valves and chips? Even if only a simple chip for stabilising the tuning voltage for a varicap tuner.

[Murphyv310]

Hi.
Some Sanyo and Sony TVs had one valve as an EHT rectifier, transistors and chips.
I believe the ITT CVC8 was multi technology with valves, transistors and intercarrier discriminator chip.
Plus the 33v stabiliser.

[Geordie McBoyne]

In 1968 introduced the Bush CTV174 colour TV set which employed transistors in the signal sections, the Plessey SL901 IC in the colour decoder and valves in the timebases. EHT was derived from a quadrupler unit replacing the 25KV overwind on the line output transformer used in the CTV162. The PD500 shunt stabiliser was retained.

Geordie McBoyne.

[ppppenguin]

We know that Thorn had a world first all solid state colour TV with the 2000 chassis. No chips either. But who was last to drop valves? Was it ITT with the CVC8? I think they made the only mass production CTV with a handwired chassis (CVC1).

[Murphyv310]

Hi
The TA7642 is a newer version of the ZN414. There are some interesting ways of improving the output anbd and changing AGC response.
On one site one person has connected the output back to the aerial coil to add reaction, I cannot see how this can work as pin three is supply, AGC and detected audio which is decoupled by a 0.1uf cap so there should be no RF on pin 3 to feedback. I though only want to use the chip as an IF amp which allegedly works very well indeed.

[Geordie McBoyne]

The Pye TCR16 car radio employed three valves in the early stages, 12BE6 mixer-oscillator, 12BA6 IF amplifier, PCL83 serving as the audio amplifier and transistor output driver. Two Newmarket V30/20P transistors in the push-pull output stage.
The HT for the valves is supplied from a circuit employing a single power transistor as an oscillator, the output is rectified, smoothed and regulated by a metrosil.
Information for this set can be found in the 1956/57 Radio and television servicing book.

Geordie McBoyne.

[Geordie McBoyne]

We know that Thorn had a world first all solid state colour TV with the 2000 chassis. No chips either. But who was last to drop valves? Was it ITT with the CVC8? I think they made the only mass production CTV with a handwired chassis (CVC1).

Hi Jeffrey,
ITT KB CVC9 colour TVs were still available to dealers as late as 1977 although it's likely production ended in 1976.

Geordie McBoyne.

[Murphyv310]

Was not the Korting hybrid CTV not a little later than the ITT?
Remember the Kuba portable colour set, virtually all valve from the early 70s.
What about the Decca Bradford and its Telefunken cousin?
B&O also had a hybrid well into the mid 70's

[radioman]

The TA7642 is a newer version of the ZN414.
....
I though only want to use the chip as an IF amp which allegedly works very well indeed.

I'm all for hybrid circuits - using the best device for each section.
However, I believe that the TA7642 is easily overloaded as it has limited AGC action, so might not be the best device to use with a valved front end.
In saying that, I've often thought that using valves for the RF stages (including the I.F. amp.) would be a good idea, followed by solid-state audio amplification.

Just my thoughts.

Andy