Vibrators

[Shannon Parks]

I was talking to the old timer at work yesterday, and he told me he was looking at purchasing a '46 Ford radio for his truck. Having never looked at one before (schematic or otherwise), I asked how the high voltage was aquired from 12V. He starting talking about vibrators and I had no clue what he was talking about. Afterwards, I recalled I had one stashed back in my desk - some gent had thrown it in with an Ebay tube purchase - a 12V Mallory G601, I believe.

OK, jokes aside, but could someone explain how this vibrator operates? Is it just a buzzer that creates a raw AC from DC? :shaking:

Typing "vibrator" & "Mallory" into Google just gives me a bunch of 976 phone numbers. :laughing6:

Shannon

[EWBrown]

No, it's not an adult toy...

What it is is a cross between a buzzer and a relay. Typical operating frequency was about 115 cycles (they didn't call them Hertz back then).
There are two versions: the simple version has four pins, and one set of contacts which alternately switch the 6 or 12 VDC to the low voltage primary of the transformer (either 12 VCT or 24 VCT). The rectification was handled by an 0Z4 or 6X4. The Synchronous Vibrator has six pins,
the second set of contacts is in sync with the "primary"set, and thusly rectify the high AC voltage by switching alternately in synch with the input.
Either way, the vibrator power supplies were nasty noise generators, and required some hefty RF "Hash" filtering to eliminate the strong Buzzzzzz that would otherwise interfere with AM reception (we're not talking FM or XM radio back then). A 1946 ford would most likely have a 6volt positive ground system.

Later on, solid state vibrator replacements came out, and these helped reduce the noise factor considerably.

Later on, car radios had 12V tubes that ran a 12V plate voltage (12AD6, 12AE6, etc) and a big fat round can germanium traisistor in a simple Class A arrangement. No HV needed. And they actually sounded pretty good.

My first car was a 1955 Plymouth Savoy that I bought for $125, when I was stationed at Fort Ord, California in 1970-71 time frame. It had a 6V positive ground system, and no radio. I scoured the local junk yards, found one with a vibrator for $5, and one without the vibrator for $3. Being the basic cheapskate, I went for the $3 option, and lucked onto a local Radio Shack store, that had a big peach basket full of assorted "stuff" by the front door. In it were two of teh correct 6 pin vibrators for my particular radio, fifty cents each. Got the radio installed.and it worked. And, yes, it was a current hog. Listening to that radio (8 tubes, PP 6AQ5s, about 8-10 watts out) with the engine off resulted in a dead battery pretty darn fast. Good excuse generator when "kanoodling" with the young ladies, watching the submarine races, but it was a real PIA otherwise.

So, in a rather large and bloated nutshell, that is Vibrators 101.

/ed brown

[Shannon Parks]

So, in a rather large and bloated nutshell, that is Vibrators 101.

/ed brown

Ed - many thanks! Pretty neat little devices - kind of like a doorbell. I punched the patent number into the .gov server (amazing site: http://www.uspto.gov/main/sitesearch.htm) - #2,732,457.

Current hog, indeed. I put it on a power supply that was current limited at 1A. With no load, the thing current limits and makes a neat buzzing like a bumble bee.

BTW, the same old ham told me about inverters that the miltary would use, that basically looked like an electric motor. Anyone know about these?

Shannon

[EWBrown]

They were called Dynamotors. Basically an electric powered motor generator. Real current hogs, but needed when a vibe wasn't enough for the job. Most are 24-28 VDC input, some 6 and 12 volt.

Lots of the WWII mil surplus "boatanchors" used these. I think I may still have a couple of small ones. Like vibrators, they eventually had solid state replacements made, this led to more modern inverters and switching power supplies.

/ed

[Shannon Parks]

They were called Dynamotors. Basically an electric powered motor generator.

http://www.surplussales.com/PowerSuppli ... rS-12.html

Checkout the WWII surplus hand crank generator at the bottom! Imagine making a preamp using that gem. Go figure that we still have this NOS surplus stuff 60 years later!

Shannon

[erichayes]

Hi All,

This brings back a few memories...

It was the Fall of 1967, and I was a Freshman in college. My first vehicle was a '65 VW Microbus, which had two things going against it as far as audio was concerned: 1. It had a 6 volt system. 2. It had an ambient noise level of around 90dB. High power transistor amps were unknown at the time, let alone ones that would run on 6 volts.

Fortunately, old tube car radios were available for literally nothing at that time (If I knew then what I know now...) and I picked up a pair of '46 Chrysler radios for a buck. These anchors used 7C5s in push-pull (the Loktal equivalent of a 6V6) and were good for around 10 watts apiece. I literally lifted the amplifier and power supply portions of the radios out and transferred them to a new chassis I punched (Japanese Greenlee ripoffs went for $9.95 for a 14 piece set back then).

I had a Concertone 727 5" reel to reel 4 track stereo portable tape deck that ran on its own 9 volt battery supply that served as the signal source, and a pair of Japanese AR-4 wannabees for speakers. My buddy and I wired the amp into the electrical system and put it on the deck above the engine compartment. We just plopped the speakers on the rear seat with 20 foot cables so we could take them out of the bus if we wanted. The 727 fit perfectly in the space between the split front seats. My buddy transcribed our records onto tape using his Sony 350, and we were ready to rock and roll.

The only car stereos around then were the Muntz 4 track and Lear 8 track aftermarket underdash units that put out about 3 watts total, and speakers that were nothing more than replacements for table radios. Just having the hardware was a sign of luxury, and that's all most guys had; there was a microscopic choice of titles available, and tapes went for $9.95 1967 dollars. Needless to say, our DIY system and tapes kicked serious ass, and made the lettermen in their fancy Pontiacs extremely jealous--except for one. He commissioned my buddy and me to make him a system for his convertible!

[Casher O'Neill]

Great VW story. I had a 68 VW Squareback, with an 8 track, a Panasonis I think. I also put some speaker in the back. I think they were 8 in" H/Ks in a nice walnut cab with a small tweeter. They rocked pretty well. The 8 track tapes were incredibly noisy. Compared to the tapes I made on my TEAC RtR they stunk pretty bad, but I got a lot of use out of it.

One of the enginers at the TV station I worked at in Peoria, IL, had a system in his cushy car with his TEAC RtR in the back seat, hooked up to some system. 10 1/2 inch reels, recored at a slow speed (It may have only been 3 3/4 ips). He said he didn't have to change tapes very often, except on long trips.

Casher