I'm so stupid... Was: Head Cleaners

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Fri Jul 2 18:36:15 2004

> A car radio with tubes, man you must be old. I was into car stereos during

I have a couple, although admittedly I don't remember them when they were
in common use.

[The zeroth generation -- too old even for me -- took the heater supply
from the car battery and used a separate HT dry battery for the anode
supply. I don't think these ever caught on]

The first generation used a vibrator to chop the DC battery voltage,
then stepped it up using a transformer. The output of that was rectified
-- either a valve, a metal rectifier, or extra contacts on the vibrator.
The rest of the radio was a fairly conventional AM superhet.

There were 2 main layous. Either an under-dash model that had everything
in one boxm or a tuner unit that was about the size of a modern car radio
(and included the freuqnecy changer, IF, and detector valves) and a
separate PSU/audio amplifier that mounted under the bonnet. This had the
advantage of keeping the vibrtor noise away from the passengers !

Second generation valve car radios used special valves, designed to
operate with an anode voltage of 12V (!) in the changer/IF stages, and a
single power transistor in the audio output stage. Trnasistors were still
expensive, and were better at audio than RF frequencies... Of course
there was no HT supply, and thus no vibrator with these models.

-tony
Received on Fri Jul 02 2004 - 18:36:15 BST