• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Why 6.3V?

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The wet cell A, dry cell B portable radio could not have been bought before 1946,

It's entirely possible that many manufacturers were producing old designs in 1945, 46 and 47. Most domestic electronics (and automotive) development and production ceased due to WWII. Back in high school (1967 to 1970) One of my friends had a 1941 Plymouth, another friend had a 1947 Plymouth. They were identical. There were few 1942 cars, and no 1943 or 1944 cars. The 1948 Plymouth had a new body style, but had the 1947 drivetrain. My 1949 Plymouth had the new engine, which had higher compression and different gearing for faster acceleration.

We didn't see premium products like the Zenith Transoceanic at the company store in Montcoal, WV; what we got was oddball products nobody else could sell.

My wife is from rural WV, and I plan to retire there in the next year or two. The whole mine worker life style has changed a bunch in the last 50 years. No more 'I owe my sole to the company store."

I grew up in Miami and my parents were middle class, but I got my early electronics fix at the local trash dump. Old TV's, radios, and HiFi sets were free for the taking. I had hundreds of tubes then too.

You didn't get TV signals up in the mountains.

Not much in the Ohio Valley either. It's Comcast or two local market Ohio channels with an antenna.

We had several channels in Miami, and I had my own junkyard TV by the time I was 10. I had the only color TV in the neighborhood when the lunar mission was broadcast in color (1971). There were about 20 people in my bedroom late at night to watch it. This embarrassed my father so much he went out and bought one.
 
In a far away land, a long long time ago.....OH, wait that's a different story.

As previously stated many houses, primarilly rural, did not have AC power. The "farm radios" of the day used a rechargeable lead acid battery for the heaters/filaments. B+ and B- were conventional dry batteries.

The heater battery needed replacement/recharging far more often than the others. Often the radio owner took the heater battery down to the local gas station for a swap out when he went to get gas for the car or tractor. The predominant rechargable technology of the day was lead acid at 2.1 volts per cell. Many tubes were 2 volts or less with a variable resistor in series with the filament which could be reduced as the battery drained.

The 3 cell battery (6.3 volts) was quickly becoming the standard in the auto/tractor industry, so the vacuum tube world adopted this voltage as the indirectly heated tube become common. Cars became bigger, with bigger engines. Better gas allowed higher compression ratios which required a bigger, higher torque starter to crank the engine. The battery cables were already 1/2 inch in diameter and getting larger every year. This prompted the auto industry to adopt the 6 cell battery in the 1950's. There was a push by the auto industry to switch to 42 volts a few years ago to reduce the copper content in modern cars, but that seems to have died.

An interesting side note:

I work for Motorola. The company's first product was a "battery eliminator". It was a power supply that operated from household power and generated the A+ (heater power), B+(plate power), and C-(grid voltage) that the "farm radio" needed. The second big product was a car radio. That's when the company changed it's name from Galvin manufacturing to "Motor" "ola", a combination of "Motor Car" and "Victrola".
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Too much power is almost enough! Turn it up till it explodes - then back up just a little.

A little more on the history of the name. Bill Lear of Lear Jet fame, designed the first car radio and worked with Howard Gates of Galvin on the mechanical packaging of it. Lear and Gates radio went on to become the first successful car radio which birthed the name of Motorola for the melding of Motor from motor car and ola from victrola as previously stated by Tubelab. This history can be found in a book titled "They Said It Couldn't Be Done", a biography of Bill Lear's life. Mickeystan
 
Lear also invented the 4 track cartridge player for use in his jets. That was the predecessor for the infamous 8 track deck that ate tapes from the late 60's until it was stomped out of existence by the CD.
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Too much power is almost enough! Turn it up till it explodes - then back up just a little.

Tubelab, I believe Lear actually developed the 8 track stereo tape player and not the 4 track. Muntz developed the 4 track and Lear invented a method to put 8 tracks of audio on the same size tape. The 8 track stereo tape head was one of many of Bill Lear's inventions. Bill had a lot of other inventions related to aviation such as the first auto pilot. Not bad for a self educated man. Mickeystan
 
I believe Lear actually developed the 8 track stereo tape player and not the 4 track.

According to Google you are right. The first 4 track I ever saw was in a Lear Jet in the mid 60's. The plane was a show piece and was on display at a local air show. Both my parents were air traffic controllers, so I got dragged to every air show within 50 miles during the 60's.

One of the local high end stereo shops (HiFi Associates) was selling Lear Jet branded tape decks for automotive use in the 60's. I assumed that it was a 4 track unit. The only thing I ever bought there was grill cloth. Even that was too expensive, but it looked cool.

If anyone still remembers Muntz, they remember a used car salesman who started making the cheapest garbage TV sets ever sold. I never knew that he actually invented anything.
 
Lear also invented the 4 track cartridge player for use in his jets. That was the predecessor for the infamous 8 track deck that ate tapes from the late 60's until it was stomped out of existence by the CD.


Ahhh, the golden daze of 8-tracks...

CD's are great, but there are some songs (especially on Deep Purple albums, for some reason) where I'm still surprised when I don't hear the track fade-out, ka-THOCK, and then fade back in to pick up.

Not that I really miss the days of having stacks of 8-track tapes on the old Vega passenger seat, tho'. Road trips in that little car would leave me rattling for days!
 
I worked as the service department manager for the largest Olson Electronics store from 1971 to 1973. Being next door to the University of Miami made the store very profitable, and we sold lots of 8 track stuff. I recorded my own 8 tracks on a Roberts 808D and there was the Thhhhwack, but no fade out or in. Track change happened in a blink. After a while you got used to it and didn't even notice it until you made a new tape.

I had a quadraphonic 8 track deck in my car and some tapes were actually mastered for the format. I still remember a Guess Who tape where the guitar floated over your head for a while and then ran around the car.

I had a quad reel to reel and several quad format vinyl systems.....Any one remember the CD-4 quadradisc??? I still have one CD-4 record, the Doobie Brothers Captain and Me.
 
Mebbe it was just that Deep Purple album had the fade...

There was quite a cottage-industry duping tapes back in those days. Storefronts would open shop in a little strip-mall, had a wall of tape decks to record whichever album you wanted for a dollar.

They lasted anywhere from a week to 6 months depending on which suburb (or unincorporated area) they were located within.
 
They lasted anywhere from a week to 6 months depending on which suburb (or unincorporated area) they were located within.

I guy I went to high school with opened one of those places near the UM campus. He was around for about 2 years. It was the IRS who finally confiscated his stuff, seems they weren't getting their share of the piracy!

I just used the Roberts machine in the store which was connected to some high end AR stuff to make my tapes.....I would never think of making an extra tape for my friends:)

Mebbe it was just that Deep Purple album had the fade...

Most of the commercial tapes used a fade during a track change if it happened during a song. An 8 track must change 3 times where the record only needed to be flipped once, so two extra breaks were required. Often this forced the 8 track to have a different playing order than the record.

The 8 track recorders of the day just changed tracks while recording when the shiney splice was detected. The most popular was the Roberts 808D and the equivalent Akai which cost about $40 more due to "fair trade" laws.
 
Tubelab, I believe that Bill Lear kept the rights to the Lear jet 8 track tape player when he sold Lear Jet as his next adventure was to build a factory exclusively for the purpose of building a 12V version of the Learjet 8 track stereo for selling into the automotive market place. The new business grew so rapidly that Bill finally sold it saying he did not want to spend another day in expansion meetings trying to keep up with automotive demand for the 8 track tape players. Bill was an impressive inventor and started and sold a number of different businesses in his life time. Mickeystan
 
I remember Muntz TVs. Had to fix a lot of them! Seems the way they were made, had to tweak a lot of resistors to make them work. I also remember Muntz Stereopack which said not affiliated with Muntz TV on them. I had a 4 track player. Not much difference between 4 and 8 track except the rubber roller was inside 8 tracks and on a lever thing for 4 track. The one I had would play the large 4 track tapes which I think were 6 inches? I could record many hours of songs on them in mono since most of the records I had were mono. But had to change tracks using a switch which was the way it was made. Here is how vibrators work. Most were 3 pins, center one was ground. The magnet coil was connected from the frame of it, ground to the pin going to the contact that would short it out when magnet pulled it, thus cutting off power to coil and energizing one side of primary winding. so went back to where it was and more until it was really buzzing. The armature had a weight on it so vibration was tuned to around 60 CPS in most and some was 115 CPS. Also some fancy 6 pin ones with a set of contacts for secondary side, so no rectifier, called synchronous.
 

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I also repaired hundreds of TV's in my early electronics career and do not have any fond memory of the Muntz brand :crazy: particularly with the sync separator circuits they employed.
In reference to the vibrator discussion, I remember the 3 pin units as being the later 12v vibrators and the 4 pin version as being the earlier 6v version. How many of you remember the 0Z4 rectifier tubes commonly found in early car radios? Occasionally, one would find a 6X5 rectifier. Mickeystan
 
do not have any fond memory of the Muntz brand

Do you remember the horizontal oscillator that got its feedback via a spring wound around the output tube? The HOT glowed red in normal operation....like some of my experiments.

We had a vocational high school electronics class where I learned how to melt tubes. The teacher often used the phrase, "Muntzing a circuit" to describe the process of removing things until it died, then putting that part back. He would ask several students to design something. The working circuit with the fewest parts wins.
 
Yes, they were 12 version used in 57 Chevy radios. Guess someone Muntz-ed those also. I have a whole case of 0Z4 tubes, but must be earlier run, marked "G" and have smaller diameter base part and no shield can.
On vehicle voltage, seems all Military stuff when I was in the Army was 24 volt battery and charge was around 28.5 volts. I had an R-392 radio and all tubes were 28 volt filament. The 28D7 put out a whopping 0.175 watt in push-pull. Aircraft was 24 volt DC for some stuff and a lot of the instruments were 110 volts 400 Hz 3 phase.
 
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