The use of valves in car radios

[Michael Maurice]

I've been following a reply to a question in the Daily Mail's questions and answers section.

Does anyone know when Valves were phased out and transistors introduced in Car Radios?

My guess would be late 50's early 60's.

Many thanks

Michael

[Brian R Pateman]

Transistors were first used in the power output stages in hybrid sets. Valves were retained in the RF and IF stages.

I can't put my hand on the file with early car radio circuits at the moment but I'd go for 1959 or 1960 off the top of my head.

Regards,

[Andrew2]

Michael - I saw that reply too and I'm not sure about it. I reckon that more recently, cars deliberately cut the juice to ancilliaries to give all the power to the starter and also to prevent 'glitching' and corruption of memory data etc.
I think you are probably right about the date.

[Michael Maurice]

My opinion too, I'm writing a reply as we speak!

[Jimmyhaflinger]

A couple of Italian makers, Voxson and Autovox, continued to make valve car radios into the early 60s.

Their later valve car radios still had all-valve circuits including the output stage, but used transistorized switchmode inverters to generate the HT.

[AlanBeckett]

There was a Thread about this last year(?) but I can't find it.
One for the Mods.
Alan

[julie_m]

Originally Posted by Jimmyhaflinger

heir later valve car radios still had all-valve circuits including the output stage, but used transistorized switchmode inverters to generate the HT.

What an odd way of doing it! If you've got transistors that can deal with enough power to run a loudspeaker via a valve, then they're surely more than capable of driving a loudspeaker directly?!

[Sideband]

Originally Posted by Jimmyhaflinger

A couple of Italian makers, Voxson and Autovox, continued to make valve car radios into the early 60s.

Their later valve car radios still had all-valve circuits including the output stage,

Appart from the very early car radio's that used vibrators to generate HT and standard valves including an output valve, I didn't think there were any 12 volt valves designed to drive a speaker. Most car radio's in the 50's and 60's used valves in the early stages and a transistor to drive the speaker. So even in the early 60's did the Italians have a 12 volt valve to drive a speaker?


Rich.

[Michael Maurice]

The question posed in the Daily Mail is:

When I am parked with the engine off and listening to the radio, why does the radio go off when I turn the engine on? This didn't happen with the cars I had in the sixties, seventies and eighties".

Answer published in the Daily Mail on Friday 26th March:

This happens in modern cars with transistor radios for the same reason that the headlights briefly dim if you start the car with them switched on, which is that the starter motor draws a huge current (more than 100 amps) leaving less for other electrical devices.

Cars of old had valve radios, which require a much higher voltage to operate than is available from the battery.

To produce this high voltage (100 - 200V) the battery feeds an electro mechanical device like a small tin can called a vibrator, so called because when energised it interrupts its feed from the battery and in falling back resumes it so that the battery's direct current is pulsed becoming alternating current.

This low voltage AC is fed into a transformer stepped up to a high voltage pulsed DC.

This high voltage is still not suitable for the radio waves, however, because the pulsing would be audible as a hum.

Therefore it is used to charge up a reservoir capacitor (which also looks like a small tin can) from which a smooth high voltage can be drawn.

The valve radio will therefore continue to operate powered by the capacitor and not the battery for the few seconds it takes to start the car

My Answer submitted this evening:

Further to the earlier answer, Valves were used in car radios up until the late 1950's / early 1960's when transistor became more widely available. After then transistors and later integrated circuits (IC's) were used exclusively in all car radios. This suited car makers, as you didn't need the vibrator to step up the voltage and early transistors being germanium were usually designed around a positive earth system which most cars in the 1960's used. When silicon transistors became available, they generally used a negative earth system but at the same time car makers were using alternators instead of dynamo's for their charging systems and at the same time switched to negative earth.

The drop in voltage when the starter motor is engaged would not have caused either valved or transistor radios to stop functioning, but in the 1990's car radios got clever, they employed computer chips to deal with tuning and other functions and these together with the newer type of power output devices (the transistors or IC's used to drive the speakers) are less tolerant of voltage drops. In order to avoid distortion and computer chip corruption, the system is simply muted until the battery can supply the full voltage. That in a nutshell is why the radio or rather car entertainment system goes off while you start the car.

The reservoir capacitor is still very much used in car radio's to stabilise the supply and filter out electronic noise that is generated by the engine and other electronic systems

Lets see if they print it!

Michael

[Synchrodyne]

Originally Posted by AlanBeckett

There was a Thread about this last year(?) but I can't find it.
One for the Mods.
Alan

See: https://www.vintage-radio.net/forum/...ad.php?t=38672

[mhennessy]

Umm,

Andrew2 is correct above. In every car I've had, the radio going off when the engine is cranked is not because of the voltage falling, but it's because the auxiliary circuits are switched off when the ignition switch is moved to the crank position, thus ensuring maximum battery energy is available for cranking.

Of course, the radio will also have a permanent live, and actually, this is where all the current comes from - in every modern (post-1990) radio I've had, the "switched live" is effectively just a control input and little current flowed into it. And that's why some can be switched on when the ignition is off (in this mode Ford radios will switch off after an hour). The Sonys I had could be powered from the permanent live (to support cars that didn't have a switched live), and when operated in this fashion, they continued playing happily during cranking. As did two Blaupunkts I had. Though I can't quite remember what the cassette deck did during cranking

Cheers,

Mark

[Zelandeth]

It's an interesting one that - think I'd also put a vote in for early 60s being the point when valves dropped out of mainstream use for car audio from the few examples I've seen.

The arrangements in cars however seem to vary wildly from maker to maker and from model to model.

Of the cars available for me to look at here, we've got several examples:

Father's car: 2010 Peugeot 207. This has a pretty clever stereo system integrated into about 20 other things in the car. When you turn the ignition off, it switches off - but you can just switch it back on again. This is all disabled when you turn the key to the start position. No idea whether its supply is actually cut of though.

2009 Peugoet 107. Stereo's live as long as the ignition is on - goes completely dead during cranking. ...Car's also under warranty still, so I'm not about to go dismantling the dashboard to check whether it's actually powered down or not though!

1994 Suzuki Cappuccino. Live with the ignition on, but ALL supply lines are cut off when cranking. Same for pretty much everything else in the car - it really does divert everything to the starter.

1995 Lada Riva 1.5E. Live all the time (there's no "accessory" position on this car's ignition. Just off, on and start), not blanked during startup. Radio seems to behave fine though...admittedly the vehicle voltage does only drop a couple of volts...mainly due to a MASSIVE battery though there!

Interesting to see the various approaches though!

[Peter.N.]

If my memory serves me correctly the Pye 1000 was the first to use a transistor, just one an OC16 as a single ended output stage - sounded very good to. I would say that was about 1960.

[mickjjo]

I believe the earliest UK hybrid car radio was the Pye TCR 16 "High Fidelity" model from 1956, ( covered in the 1956/7 R+TV servicing book). This used 3 valves, 12BE6, 12BA6, PCL83, and 3 V30/20P power transistors, one as an inverter for the HT to the valves and two as a 4 watt push pull output stage. I have never seen one of these sets. The Motorola 77M seems to be one of the last valve/transistor hybrids using 12v HT valves in 1962.

Regards, Mick.

[fidobsa]

Interesting stuff. I had always wondered how they got the HT in valve car sets and had thought perhaps they needed an additional HT battery like the portable sets.

[Jimmyhaflinger]

Originally Posted by Richard_Newman

Appart from the very early car radio's that used vibrators to generate HT and standard valves including an output valve, I didn't think there were any 12 volt valves designed to drive a speaker. Most car radio's in the 50's and 60's used valves in the early stages and a transistor to drive the speaker. So even in the early 60's did the Italians have a 12 volt valve to drive a speaker?


Rich.

Those old Italian car radios used regular high voltage radio valves in B9A and B7G envelopes, including the output pentode, and had a built in transistorized high frequency switchmode inverter (instead of a mechanical vibrator) to generate the 200v HT

This allowed the use of cheap reliable valves instead of exotic and troublesome 12v valves.

I have an Autovox radio from 1961 with the transistorized HT inverter and it still works great!

[Waveguide]

Hello, I am assuming you are referring to broadcast car radios. I can't be specific about these, but I do have a HUDSON FM208 4M mobile which still works and this uses valves for the Tx section and transistors for the Rx. The manufacturing date for this set was around 1964/65. I am modyfing the set to work on 2M as we don't (yet?) have 4M here in Holland. 73'Alex,

[Michael Maurice]

I'm talking about in car stereo and radio systems, the sort of car radio/audio system that are either fitted as standard by the car maker or retro fitted at a later stage.

[vinrads]

Hi nobody has mentioned the special valves ECH83 EBF83 these were designed to work on 12 volt ht and with a transistor output stage ,no vibrator or inverter was required, regards Mick. oops just noticed Ritch mentioned them .

[cheerfulcharlie]

my ten pence worth, from old memories maybe wrong?

My dad's early 1961 reg car had a Pye valve radio fitted. There was a multicore cable going from it to another box which was situ somewhere near the heater blower.
On this box was a chunky power transistor with the whole box presumably acting as a heatsink , at the other end of this mysterious box was the speaker output.
no idea what that box was all about

the radio was brill though, medium wave was so much more suited to the car
than crappy FM.

His 1965 car radio was all transistor with those brilliant mechanical selector buttons...once again something that worked very well compared to all the nonsense you have to go through today just to find a station and hold it for 10 minutes.