From: Philip Nasadowski
Subject: Re: Digital divide by ten, 1949 style
Date: Sun, 15 Sep 2002 19:51:59 -0400
Organization: Biker/metalhead from hell!!!
References: <3D84D4B3.50B511EF@webaccess.net> <3D850A3C.31381AD5@webaccess.net>
NNTP-Posting-Date: 15 Sep 2002 23:55:17 GMT
X-Harley: '99 FXDWG
User-Agent: MT-NewsWatcher/3.1 (PPC)
In article <3D850A3C.31381AD5@webaccess.net>,
Chuck Simmons wrote:
> I did run across an oddity I had forgotten about. There was an AA5
> variant that used a rectifier with a 117 volt filament. The other tubes
> had 1 volt filaments. These were rare indeed.
Some battery portables had this, to allow 'plug in' operation, and
> There were a couple of other AA5 variants that existed. Car radios were
> essentially the AA5 but the tube numbers all began with 6 and then
> latter 12. The plate supply in car radios was derived from a vibrator
> and tube rectifier or else a vibrator with synchronous rectifier
The 6.3 volt supply almost all transformer type tube equipment in the US
used was because or early car radios.
Tubes were first all 2.5 volt (for whatever reason), but then they
became 5 volt (briefly). When someone thought of the car radio, it was
natural tto use the then 6 volt car battery to run it, so RCA and all
developed 6.3 volt tubes. The first number in a US tube type, but not
CRTs, generally indicates the voltage needed on the filiment. Thus, a
6BA6 was 6 volt, a 12BA6 was 12 volt. On a CRT, the first numbers
indicated the screen size (in inches), and the P* at the end the
phosphor. P4 is B&W TV, P22 is color.
Rectifier tubes were 5 volts for years, thus transformers had a 6.3 V
winding (or a tapped 12V), a 5V winging, and whatever high voltage and
others were needed. 6 volt rectifiers appeared later on, though the 5Y3
and 5U4 held on.
> True but the comment was more about the superheterodyne than the 6BE6.
Oh, the 6BE6 sure can go high, RCA said it was suitable for FM broadcast
radio use too.
> TVs used germanium diode mixers fairly early on. I forget the earliest
> tuner I saw that in but it had to be circa 1950 when TV came to the city
> in which I lived.
No, they used diode mixers for UHF. UHF has always been diode mixers,
from day one. VHF tunners were pentode mixers even into the 60's. The
UHF tunners had a 1N81 or something like that as the diode mixer (I
never understood how that worked), and later had 1 or 2 varactor diodes
for AFC. Most TVs used semiconductor diode detectors, as early as '52
or '53. I have a Bendix where the video was dead. It was the
*semiconductor* diode detector that was dead. None of the tubes were!
VHF was pentode (or triode in some early sets), UHF was diode.
> The foreign tubes tubes were challenging to get in the US in the 1950s.
Most were, but stuff like the ECC83 were easy, if you knew what their US
cross numbers were.
What I never got was, even today, the high power sweep tubes used in
color TVs are $$$, even though there's no demand for them, except for
the %&%^&%^$& hams and audiophools, how think any tube that can handle
power MUST be placed into some stupid use it wasn't designed for.
Though my favorite was still the audiophool amp that used like 50 12AX7s
in a push pull and (very) parrallel output stage...
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