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Using Battery for 300v B+ ?
Using Battery for 300v B+ ?
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Old 5th March 2009, 08:40 PM   #11
Tweeker is offline Tweeker  United States
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Spark gap transmitter:
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Be sure your foil hat has a good low impedance ground.
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Old 5th March 2009, 09:51 PM   #12
Tubelab_com is offline Tubelab_com  United States
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Anyone remember all this ??
I remember, but the one thing that no one has recalled yet is the 0Z4. Anyone remember that one?

Basically there were 3 evolutionary paths. The home radio receiver, the portable, and the car radio. Home radios started out with tubes like the 01A that used a 2 volt battery for the filaments (the A battery) and a 45, 67.5 or 90 volt battery (the B battery) for the B+ (this is where the name B+ comes from) and a 15 or 22.5 volt battery (the C or C- battery) for bias. in the 1930's the Galvin Manufacturing Company (now Motorola) invented the battery eliminator which was a fancy name for a line powered power supply.

There were attempts to stuff all of this into a box and make it portable. This idea didn't take off until the octal "battery tubes" appeared with their 1 and 3 volt filaments. About the same time Eveready figured out how to stuff all 3 batteries into one case and size them so they all ran out at the same time. Portable radios became a reality, and then the 7 pin miniature tubes came out and made them actually portable. Ballast tubes, 117Z3's and selenium rectifiers made it possible for battery or line power in the same radio. The most collectible being the Zenith Transoceanic.

The Galvin Manufacturing Company figured out how to put one of these things in a car so they changed their name to Motorola, Implying motor and music. The early radios used the vibrator mentioned earlier and a specialized transformer to generate high voltage that powered a typical 6 tube radio. Automobiles had a 3 cell battery that delivered 6.3 volts (does that number sound familiar?) from their inception until the mid 1950's. Some car radios were in reality decent sounding HiFi sets on wheels. My first car was a 1949 Plymouth. The factory radio used vibrator power to generate 300 volts of B+, rectified by an 0Z4. The amplifier had two 6V6GT's in push pull delivering about 10 watts to a 6 inch speaker in the dash. I mounted two of these radios in the trunk wired up to 6X9 speakers on the deck lid connected to a Panasonic portable cassette player for some serious mobile vacuum tube vacuum tube rock music in 1970.

In the 1950's cars went to 12 volt electrical systems. The space charge vacuum tube was invented. It ran with 12 volts on the plate but couldn't generate any serious audio power. The germanium transistor solved that problem, so the vibrator based power supply dissapeared from the car audio market. They were still used in some mobile transmitters until the germanium switching transistor made it vanish altogether. Car radios used 5 tubes and one big output transistor. Then the little 3 legged fuses got all of the tubes voted off the island.

Does anyone know what the waveform was like for these vibrator circuits?
It resembles a square wave if the vibrator is in good shape and the snubber caps haven't fried. The operating frequency is usually 40 to 100 Hz.

I was wanting to generate a very clean 300 B+ from 12v I will look at using an inverter.
The germanium inverters used in mobile tube type transmitters run at 800 Hz to 2 KHz. It is nearly impossible to keep that whine out of the audio system. I tried putting the inverter under the hood next to the car battery, but the whine was still there.

Modern AC inverters for operating AC appliances in the car work by stepping 12 volts up to about 150 volts and then chopping that up at 60 Hz. The inverter runs in the 50 KHz range and can be used to make about 300 VDC with a voltage doubler.

The 0Z4? That was a gas rectifier that had no heater. AC in DC out, no heater required. The glass ones (rare) exhibit a familiar purple glow.
Tubelab, it's 5 year mission. To explore strange new tubes, to seek out new circuits and topologies, to boldly go where no tube has gone before......
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Old 6th March 2009, 03:54 AM   #13
Mickeystan is offline Mickeystan  United States
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Default Hey Tubelab....

I remember the OZ4 well. Do you remember that 6 volt vibrators were made with 4 pins in an arrangement like the 300B tube meaning two big pins and two small pins. Also, the 12V vibrators had only 3 pins. If your memory is real good, you will also remember it was very common in early 50's car radios to mount the vibrator power supply and the audio power amplifier on the speaker assembly and cable it back to the radio.

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Old 6th March 2009, 06:38 AM   #14
richwalters is offline richwalters
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A bit of heritage is quite in order. The Radiotron hd bk has (as expected) as massive chapter related to vibrator psu's. As Tubelab mentioned the gerrm transistor, I am fortunate to have some popular ones in my pit. For amusement value only, the one in the centre photo which looks gold plated is one of the earliest produced in the 1950's.
The RF ones OC44 etc had a bandwidth which fell short of the SW band and the others mainly audio OC71 AC128 etc were hard pushed at 15Khz if that.
Of no commercial value, except the lovely low Vbe drop of only 0.2V all germaniums were photo sensitive hence the black paint. Others canned.
It does seem concidental that the modern day SS switching power supply as we know it has it infant days with the old vibrator. A quantum leap.

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Old 6th March 2009, 07:41 AM   #15
EC8010 is offline EC8010  United Kingdom
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Originally posted by richwalters
... all germaniums were photo sensitive hence the black paint.
Actually, all semiconductors are photo-sensitive. We had a fascinating demonstration of this recently at work. We needed an inverter to produce 5kV at negligible current, so we made a little oscillator with a transformer to step it up to 500V, then added a voltage multiplier to get the 5kV. But it didn't work when a bright light was shone on the EHT diodes in the voltage multiplier. It turned out that what was happening was that the photo-electric effect was producing a small voltage across each of the diodes that was enough to switch off the op-amp controlling the oscillator. A strip of black insulating tape over the (glass encapsulated) silicon diodes stopped the problem.
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
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