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 Post subject: Whatsa Vibrator? Keep it clean!
PostPosted: May Sat 20, 2006 1:33 am 
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Location: Riverview, FL
Just purchased a Zenith 4B313 off e-pay and the schematic shows it has a vibrator.

What is it? What does it do? How can you check to see if they are good? Are their replacements still available if it isn't?

I'm ready to be edumacated!

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 Post subject:
PostPosted: May Sat 20, 2006 1:58 am 
Silent Key

Joined: Jan Thu 01, 1970 1:00 am
Posts: 20548
Location: Sandpoint, IDAHO 83864
A vibrator is an electro-mechanical switch that operates off of DC power, like from batteries. The construction is similiar to a door bell or buzzer in that there is an electromagnet and when power is supplied, it pulls an armature towards it. When the armature moves so far the circuit is opened or shorted out and the electromagnet loses its magnetism and the cycle gets repeated over and over again as long as the DC power is supplied.

Along with the armature, there are a set of contacts that switch the DC voltage to each side of a transformer primary winding. Transformers do not operate on DC, but they work fine on interrupted DC and that is what you have. Vibrators are also known as mechanical interrupters, by the way. This interrupted DC is stepped up in the transformer and rectified to provide the B+ for the set.

This is a very crude explanation, but if you want more, try to dig up some older ARRL handbooks, say, before 1970 and they have a good explanation of them, synchronous and non-synchronous types and such. They are still available in some places, but are getting very expensive. Some have used solid state replacements to some degree of success. If you are familiar with older car radios, the vibrator is what makes the humming sound when the set is turned on.

One thing to always remember is that the "buffer" capacitor that is across the transformer secondary is critical in its value. It should always be replaced whenever the vibrator is replaced and its value strictly adhered to along with its rather sounding high voltage rating. Voltage ratings of 1600 to 2000 volts are not unheard of.

Hope this helps a bit.
Curt

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 Post subject:
PostPosted: May Sat 20, 2006 2:02 am 
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Thanks Curt. Were these used as cost saving measures? Is there an advantage to having or not having them in regards to design?

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 Post subject:
PostPosted: May Sat 20, 2006 2:06 am 
Silent Key

Joined: Jan Thu 01, 1970 1:00 am
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Location: Sandpoint, IDAHO 83864
Well, for one thing a vibrator power supply was the ONLY way to obtain B+ voltage for sets, unless they wanted to use a dynamotor, which is really less efficient and more troublesome in the case of car radios. I don't think of it as a cost saving measure, as they didn't have much of any alternative choices. All manufacturers used them.
Curt

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 Post subject:
PostPosted: May Sat 20, 2006 2:49 am 
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Tu-be or not Tu-be wrote:
Were these used as cost saving measures? Is there an advantage to having or not having them in regards to design?

There was no option. Vibrators were the only way to create AC from DC (disregarding dynamotors) until transistors came along. The vibrator is much older technology, having been developed in the late 1920's or early 1930's, and commonly used in 32-volt farm radios of the time. Also used in automobile radios well into the 1960's.

Vibrators create a square wave which is used to drive a transformer. The most common operating frequency is 115 Hz, although there is some variation, mostly to higher freqs. And as Curt said, the value of the buffer capacitor is critical to proper performance of the supply. Try to match its value to two significant digits.

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Last edited by Leigh on May Sat 20, 2006 2:54 am, edited 1 time in total.

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 Post subject:
PostPosted: May Sat 20, 2006 2:53 am 
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Well, there's always dry cells, Curt. :)

Your radio was intended to be used on a farm where there was no electricity. This set was designed to run off of a single 6V lead acid battery, as found in a car or tractor. The vibrator converts the 6VDC to, effectively, 6VAC which is stepped up by a transformer to 130VAC or so. Then this is converted to 170VDC which becomes B+.

Vibrator power supplies are a bit more complex than AC power supplies.


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 Post subject:
PostPosted: May Sat 20, 2006 3:53 am 
Silent Key

Joined: Jan Thu 01, 1970 1:00 am
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Location: Sandpoint, IDAHO 83864
Well, if I had my choice, they would have been dynamotors!

By the way, have any of you ever thought of why the armature of most vibrators short out the coil instead of simply opening up the circuit?

I know Norm knows, so think about it a bit.
Curt

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 Post subject:
PostPosted: May Sat 20, 2006 4:16 am 
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Leigh wrote:
Also used in automobile radios well into the 1960's.


I dunno what you were driving back then, but American vehicles with radios by Motorola, Bendix, Delco, etc. were using the low voltage Space Charge tubes by the late 50s... AF output was handled by a large germanium power transistor(or two)....

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 Post subject:
PostPosted: May Sat 20, 2006 4:19 am 
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Curt Reed wrote:
By the way, have any of you ever thought of why the armature of most vibrators short out the coil instead of simply opening up the circuit?

Hi Curt,

The shunt-drive configuration which you described has a couple of advantages. 1) All contacts are open when at rest. 2) It requires no additional contacts in the vibrator.

The separate driver system requires an additional set of normally-closed contacts. This system is preferred in low-voltage or high-frequency applications.

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 Post subject: Re: Whatsa Vibrator? Keep it clean!
PostPosted: May Sat 20, 2006 5:27 am 
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Location: Colorado Springs, CO
Tu-be or not Tu-be wrote:
Just purchased a Zenith 4B313 off e-pay and the schematic shows it has a vibrator.

What is it? What does it do? How can you check to see if they are good? Are their replacements still available if it isn't?

I'm ready to be edumacated!


Maybe this will help.

http://radioremembered.org/vpwrsup.htm


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 Post subject:
PostPosted: May Sat 20, 2006 6:34 am 
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Location: Lakewood, California
35Z5 wrote:
Leigh wrote:
Also used in automobile radios well into the 1960's.


I dunno what you were driving back then, but American vehicles with radios by Motorola, Bendix, Delco, etc. were using the low voltage Space Charge tubes by the late 50s... AF output was handled by a large germanium power transistor(or two)....


He could have been driving a Mercedes or Porsche with a Blaupunkt Bremen or Wolfsburg radio--if I remember right they were still vibrator powered in 1960.

True, most major U.S. auto radio manufacturers had gone hybrid by 1958, but there were a few hold-outs.

Here's a list of Delco radios still using vibrator power supplies in 1959:

1958/9 Studebaker/Packard manual tune Delco AC-2905

1958/9 Vauxhall Delco 988946 or 989578

1959 Willys Delco 815395

1959 GMC truck Delco 2233398 (and I think the 57/59Chevy truck radio).

Some of the after-market radios (Sears, etc.) were still selling some vibrator powered sets in the early 1960's

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 Post subject:
PostPosted: May Sat 20, 2006 6:38 pm 
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Back in 1973 when I bought my 1956 Cadillac DeVille, it had a non working wonderbar radio. It was a 2 chassis radio, seperate amp-twin speakers.

The vibrator was not working , so I took it apart, and cleaned off the contacts, and it worked for as long as I owned the car! about 15 years.

I was lucky, I guess. Boy do I remember, it had an auful smell to it when I opened up the can! :shock:

I still have a Bogen P.A. Amp that has 2 vibrators in it, one for the B+, and the 2nd one is for the turn table motor.( has a built in turntable on the top of the amp)

It was designed to run off of 110 volts ac and 6 volts DC.

Dennis.

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 Post subject:
PostPosted: May Sat 20, 2006 6:58 pm 
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Location: Circleville, OH, USA
Yeah, Dennis, I remember that odor. The can was lined with sponge rubber to dampen the sound and that's what smelled.

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 Post subject:
PostPosted: May Sat 20, 2006 8:54 pm 
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Location: Valley City ND USA
Hi, The 58 Cad radio I did a while back was a vibe. type too 35Z5.


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 Post subject:
PostPosted: May Sat 20, 2006 10:11 pm 
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Thanks Bill that was a great link. I will be visiting customers in Colorado Springs on Tuesday. Small world.

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 Post subject:
PostPosted: May Sun 21, 2006 12:10 am 
Silent Key

Joined: Jan Thu 01, 1970 1:00 am
Posts: 20548
Location: Sandpoint, IDAHO 83864
Youse guys complain about a selenium rectalfire burning, but you have never smelled the innards of a vibrator when they are opened up! For years, I always thought they contained some mystery gas that prevented oxidation of the contacts or something. About fifteen years ago, I opened one up on the kitchen table to clean the contacts and I was accused of eating too much sauerkraut and weinies the night before!
Curt

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 Post subject:
PostPosted: May Sun 21, 2006 5:57 pm 
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Curt;
The way a vibrator works,
Would you call that a half wave AC ?
Dan


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 Post subject:
PostPosted: May Sun 21, 2006 6:08 pm 
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Hi Dan

A vibrator has two sets of contacts. It's set up like full wave but can't really use this description.

Full wave & half wave describes DC rectification. With full wave both halves of the cycle are used. Half wave, only one. DC pulses from a full wave rectifier are right next to each other so easier to filter. In a half wave circuit 50% of the time no voltage is supplied so larger filter caps are required to hold voltage steady.

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 Post subject:
PostPosted: May Sun 21, 2006 6:17 pm 
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Actually the outgassing of that rubber sleeve is destroying the contacts on vibrators that are not used. They do stink really bad when you open them up. The sulfur compounds in the rubber are turning the contacts black and coating them with an insulating film. I have had more than one which were so bad that no amount of cleaning would make them work again, and these were NOS right out of the box.

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 Post subject:
PostPosted: May Sun 21, 2006 6:30 pm 
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panther wrote:
The way a vibrator works, Would you call that a half wave AC ?

Hi Dan,

Vibrators are available in several configurations.

The simplest is a single SPDT switch which switches voltage (or ground) alternately to one end or the other of the transformer primary, while the center tap is fed from the ground (or voltage) side. This produces an AC output at the secondary which is rectified by conventional means, either solid state or cold-cathode tube rectifiers like the 0Z4.

The synchronous vibrator has an additional set of SPDT contacts which are used on the secondary side of the transformer. Since the polarity of the induced voltage is known, you can switch one end or the other of the secondary to the B+ line with the center tap grounded. This provides "pseudo-rectification" in that the voltage sourced from the transformer is always positive. No additional rectifier is used in this configuration.

You'll find vibrators with anywhere from three to eight pins. Some of the configurations are rather odd.

{edit 5/23 additional info}

Your Zenith 4B313 uses a Radiart 5435 or ATR 5435 or Mallory 1808/4546 with two .01 mfd 1600-volt buffer caps. DO NOT use a lower voltage rating.

The vibrator may also cross to any of the following, but these should be considered second choices:
ATR 332, 527 or 549
Cornell-Dubilier D11, D21, D34, D35, 5411, 5621, or 6821
Delco 8519, 8538, 8613, or 8634
Note that these are "reverse" cross-references and may not work properly in your radio.

You'll find NOS vibrators available from many vacuum tube dealers. But there are many different numbers, and they're seldom interchangeable. Some of the major manufacturers were ATR, Cornell-Dubilier, Delco, Meissner, Mallory, Oak, and Radiart. If you have one manufacturer's number we can usually cross-reference it to other brands.

There are also solid-state replacements, but they have a poor reliability record. YMMV

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http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


Last edited by Leigh on May Mon 22, 2006 8:02 pm, edited 9 times in total.

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