Why 6.3 volts?

the voltage on a fully charged 6V lead acid battery?

-Lasse

** Like 1.25V and 12.6V.

** All three voltages ( and many more) relate to the use of cells or batteries being used to power the filamants. 1.25V is in the middle of the discharge voltage range for a nominal 1.5 V dry cell and spot on for a NiFe cell.

Similarly, 6.3V is in the middle of the discharge voltage range for a 3 cell lead-acid battery.

... Phil

I would guess 3 lead-acid cells was a reason. Nominal 6 volt batteries were very common back in the 1920s-40s, when this stuff was orginally developed.

When indirect heated cathodes were developed, it made sense to use AC, but at the same voltage as the original DC supplies.

Interestingly 5 volts was also very common for direct heated things like rectifiers. But a bit rougher than the 5 volts used in the digital world.

--
Regards,

Adrian Jansen           adrianjansen at internode dot on dot net
Note reply address is invalid, convert address above to machine form.

"Adrian Jansen"

** Be a bit perverse to use a battery to power the heater in a rectifier tube.

... Phil

The first digital ICs were RTL, and the common supply voltage was 3.6 I think. Horrible little things.

John

And almost every PC has a 3.3V buss.

--
Virg Wall, P.E.

Things are creeping down. The core voltage on the Altera FPGAs we're using is 0.9. We're running a lot of the i/o banks at 2.5.

John

Of course! It remembers me to a thingy that use battery power, need charge everyday, only to power a huge minicontroller to run a java interpreter in case you like to view a video when you are on your every day-way or collect data of your life to bothers you with battery powered comercials.

But fortunatly people are smarter than there phones? :-D

Olaf

A simple answer. Kind of makes me ask "why didn't I think of that" :) Yep, 2.1 v per cell, still the same today for lead acid batteries except they are all 12v today. Actually 12.6, but I've never heard the .6 used for a car battery.

I recall the old carbon zinc flashlight batteries were 1.5 volts, so this all makes sense now, except using 4 of them would yield a straight 6.0v.

I remember back in the 60's my uncle gave me and old tube radio that required a battery that was (if I recall correctly), 90 volts. It was a large brick type thing. I suppose it contained a whole bunch of individual carbon zinc cells (I guess that would be 60 of them). The radio was really old (at that time). I never could find a battery for it, and if I had, I can imagine the cost was quite high. (Not to mention the were not rechargable, just throw away type). This must have been the original, first portable radio..... I dont know what ever happened to it, or remember the brand. I was probably in my early teens at the time. Had I been older, I would have probably made a power supply for it.

Yea, all those old tv power transformers were 5V 6.3V and some high voltage with a center tap. The 5v was usually for a 5U4 or 5Y3. For older audio amps, they also had the 5 and 6.3. but the later audio amps had the 12.6V center tapped, which supplied the 6.3 and 12.6 for the very common 12AU7, 12AT7, etc. Most of those sets were using silicone diodes for rectifiers, or the layered selenium type which seemed to fade quickly.

I also remember the line voltage radios that used 50C5, 35W4, and three 12v tubes such as 12BE6, 12BA6, 12AV6 to achieve 120v. Those radios were dangerous with their live chassis. I got shocked several times on them.

Yet the older ones had a 50C5, 35Z5, 12SQ7, 12SA7, and 12SK7 or 12SN7 (OCTAL base).

It's funny because I never forget those common tube numbers

Then there was the 50L6, which I would have thought was a 6L6 with higher filament voltage, but the 50L6 never had as much power as a

6L6. But that was probably due to lower plate voltages.

I always liked working on tube circuits, mostly due to point to point wiring. The solid state devices were never as easy to work on, and the printed circuit boards made building stuff difficult without special board etching equipment.

On a sunny day (Sun, 11 Dec 2011 11:57:54 +1100) it happened "Phil Allison" wrote in :

Well I actually did that in my first 10 kV setup. Not enough isolation in the transformer.

Since the rectifier cathode sits at the anode voltage line potential at a few hundred volts, a separate secondary winding was required to feed the rectifier filament, thus it was irrelevant if 4 V (AZnn) or 5 V (GZnn) was used.

When you figure this out, could you then let us know why they charge the $0.009 cents on each gallon of gasoline (in the US)?

As to the 6.3, tubes were just a little before my time. Other than the seemingly correct answers already provided, having the ".3" lends an arbitrary precision. If you just said "6", someone might think "5" would be close enough. Say "6.3", and they're likely to re-think it.

ACtually they are not..

a fresh carbon cell should yield ~ 1.578 volts. which equals ~ 6.3 volts DC. We used that as a calibration source years ago.

Jamie

They don't. They give you $.001 off. It's called "marketing". It's like paper $1 bills and the Imperial system; inertia is sometimes tough to overcome.

Ding! Perhaps carbon zinc or such for handheld radios, etc. I had one that used 63 volt batteries. No lead acid though.

Back then, designs had to follow available elements (not that they no longer do). So designers formed the standards entire industries had to follow so things would all work properly.

It may have to do with a certain size nichrome wire and the folks arriving at some ideal voltage to feed some ideal length heater wire, which the industry then adopted as a standard.

Kind of like Edison's light bulb base. On a 120 volt light bulb, the filaments are the same length, and the diameter of the wire is reduced to increase wattage and brightness, but usually means a decrease in lifespan. Vacuum tubes have to live a long life, but create enough heat to function. There is a happy point in nichrome wire where lifespan and brightness and power consumption all cross (or they engineer guy says "That's a good spot"). At some point the entire group sets a standard an entire industry follows.

These days, we have "associations" of manufacturers whom all agree to agree with each other.

Back then, the first one to market with something new could set down the way it gets done by all their competitors in the future.

It does sound funny.

TTL used to be 5 Volts (still is), but we have slowly whittled that down because it is quicker to slew less between a 1 and a 0 and it consumes less power. They are operating at far lower than 3.3 Volts now.

It's actually an anti-rounding down that avoids a tax increment.

John

I never knew this..... I've always seen them listed as 1.5 volts and that's it..... (That must be after 5 minutes of use) :)