Vintage Audio Activities...

[xantia_v6]

I knew someone who had one of those in an early 80s BMW 735. He didn't like it much. Too fiddly and difficult to operate by touch with the gooseneck moving around.

[mickthemaverick]

IIRC London cabbies had a similar device to control the meter!!

[NewcastleFalcon]

Chris' "pretty little Red Corvette" here

viewtopic.php?p=806992#p806992

Led to this

Supposedly "State of the Art" at the time...Interesting or Awful


Chevrolet Corvette Transistorized Hybrid Car Radio-1956
Historianbuff, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

Neil

[CitroJim]

Excellent Neil... I repaired a few hybrid car radios back in the 70s... They took a lot of current and one thing you never did was listen to it with the engine not running... If you did you'd likely need a bump-start to get going again due to a flat battery!

[Peter.N.]

I remember those Jim. 0C16 output? I had a Pye, 2000 or 3000 was it, sounded very good.

Peter

[NewcastleFalcon]

moved edited in some pics

[CitroJim]

I remember those Jim. 0C16 output? I had a Pye, 2000 or 3000 was it, sounded very good.

Peter

That's it Peter, either an OC16 or OC26 in Class A along with the special 'space charge' valves that would operate with an HT of just 12 volts, typically with an ECH83 as the mixer/oscillator and an EBF83 as IF and detector/agc. If it was a hybrid VHF set you may find an ECC86 and an EF98 in there too...

All quite rare now. Valves were used as the transistors of the day were basically good only for audio frequencies.

The big OC16/26 transistor as the Class A output device along with the valve heaters really mopped up the juice from the battery!

Fascinating sets and these days, very collectable...

[NewcastleFalcon]

Go on Peter and Jim have a plough through the spec for the radio from "The Radio Museum" and see if there is anything worthy of comment

https://www.radiomuseum.org/r/chevrolet ... 25156.html

Chevrolet 3725156 Corvette United Motors Service (Delco)
Country United States of America (USA)
Manufacturer / Brand United Motors Service (Delco)
The Valves

The Transistors

Neil

[Peter.N.]

Jim

The 0C16 looked like a little barrel with an 0 BA stud on the end, Don't think I have seen one since I had my radio, super quality for a single ended output. I was told that the series of valves used in those sets weren't specifically designed for 12 v operation but were carefully selected from the standard range.

Neil

Was that the radio that had an electric motor driving the tuning which was stopped when searching by the rise in voltage on the AGC line? If so I had one in for repair from a scrapyard many many years ago. The 12X4 is obviously a rectifier and the ECC82 I am well familiar with but not sure about the others. Give me a Mullard number and I will tell you what it is even if I haven't seen one, I'm sure Jim could too.

Peter

[NewcastleFalcon]

...The 12X4 is obviously a rectifier and the ECC82 I am well familiar with but not sure about the others. Give me a Mullard number and I will tell you what it is even if I haven't seen one, I'm sure Jim could too.

Each of the tubes in the picture have a reference page on the Radio Museum Site

12BA6	link https://www.radiomuseum.org/tubes/tube_12ba6.html
12BE6	link https://www.radiomuseum.org/tubes/tube_12be6.html
12BF6	link https://www.radiomuseum.org/tubes/tube_12bf6.html
12AU7	link https://www.radiomuseum.org/tubes/tube_12au7.html
12X4	link https://www.radiomuseum.org/tubes/tube_12x4.html

Neil

[bobins]

That's it Peter, either an OC16 or OC26 in Class A along with the special 'space charge' valves that would operate with an HT of just 12 volts, typically with an ECH83 as the mixer/oscillator and an EBF83 as IF and detector/agc. If it was a hybrid VHF set you may find an ECC86 and an EF98 in there too...

I understood everything you said there Jim, ..... everything up to and including the word 'Peter'

[CitroJim]

That's it Peter, either an OC16 or OC26 in Class A along with the special 'space charge' valves that would operate with an HT of just 12 volts, typically with an ECH83 as the mixer/oscillator and an EBF83 as IF and detector/agc. If it was a hybrid VHF set you may find an ECC86 and an EF98 in there too...

I understood everything you said there Jim, ..... everything up to and including the word 'Peter'

At least some of it was comprehensible Robin

[NewcastleFalcon]

Neil

Was that the radio that had an electric motor driving the tuning which was stopped when searching by the rise in voltage on the AGC line? If so I had one in for repair from a scrapyard many many years ago.

Peter

This may or may not answer that question Peter

The Delco Radio Model 3725156 is a battery operated, custom built AM automobile, auto signal seeking receiver with four transistors and six tubes and sold as an option for the 1957 Corvette. The signal seeking function is triggered by pushing the bar marked “WONDERBAR” on the front of the radio. The radio will then mechanically tune to the next station.

This optional radio was fitted to 3635 of the 6339 Corvettes built in 1957.

It was Option 102 and cost $199.10.

Neil

[CitroJim]

Jim

The 0C16 looked like a little barrel with an 0 BA stud on the end, Don't think I have seen one since I had my radio, super quality for a single ended output. I was told that the series of valves used in those sets weren't specifically designed for 12 v operation but were carefully selected from the standard range.

The OC26 was basically the same transistor Peter but in a TO-3 package. A single-ended Germanium Class A amp does sound very good as there's no crossover distortion. Another reason for the use of a transistor in the output stage was the inability of a 12V valve to produce sufficient audio power to be effective in a noisy car and the inability of an HT power supply (at the time) to provide sufficient current to allow an ordinary output valve to be used.

Before 12V valves came along, ordinary valves were used in the RF, IF and first audio sections with their HT needs (around 200-250V) being fulfilled firstly via a power supply incorporating a vibrator and later, a transistorised inverter. Those were very thirsty for battery juice as they were not hugely efficient.

None of the valves you list are particularly special or specifically intended for car radios Neil, their only benefit in a car radio was they all have 12V Heaters.

The Exx83 series valves were generally specifically intended for car radios - although there were expectations such as the PCL83 for TV applications and the famous ECC83 (12AX7) which has now achieved legendary status in guitar and boutique Hi-Fi amps and is still in volume production.

The lovely thing about the European valve coding is you can readily identify exactly what it is from its code. An EBF83 for instance being a double diode and signal pentode with a 6.3V 300mA heater. With the American numbering series you can only tell the heater voltage and how many electrodes it contains - a 12AX7 has a 12.6V heater (actually two 6.3V ones with centre-tap) and 7 electrodes. It's European designation ECC83 immediately identifies it as a double small signal triode with 6.3V heaters...

I could go on... I, like you Peter, prefer the European nomenclature for valve designations.

[NewcastleFalcon]

The lovely thing about the European valve coding is you can readily identify exactly what it is from its code. An EBF83 for instance being a double diode and signal pentode with a 6.3V 300mA heater.

To the uninitiated that appears to have no logical use of letters and numbers to translate EBF83 into double diode and signal pentode with a 6.3V 300mA heater. I presume it just does

Maybe its like the Chinese takeaway system where 81 translates into Sweet and Sour Chicken with fried rice

Neil