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Need Vibrator Help




 
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WU2D
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« on: November 04, 2012, 11:57:24 AM »

Not that kind of vibrator Al...

I have the shack somewhat back in operation; a little late this Fall but the first project beyond getting my antennas in shape is an authentic Vibrator Power Supply Unit for my PARASET transciever. Yes I am rejecting the solid state and am going with the original design.

The idea was to find a safe spot to transmit like the second story of a building. You grabbed your Paraset and dropped a wire out the window. If there was no 230 VAC power, you  removed your 6V car battery and lugged it up to the room. The BBC was copied, perhaps even a short transmission was made and you quickly got out of Dodge before the German RDF got you. The device to produce 350VDC was a simple vibrator power supply, usually built into the small suitcase which also housed the XCVR and AC supply.

I think I found a suitable vibrator and transformer. The vibrator appears to be a Motorola (Part # 3333) and to test it I hooked it up per the "standard" 4-pin non-synchronous chopper- type circuit with an old 6.3 VAC fillament transformer. It buzzed happily and made HVAC with 6VDC.

MIke WU2D


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WQ9E
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« Reply #1 on: November 04, 2012, 12:57:17 PM »

Mike,

I am no expert on vibrator supplies but your buffer capacitor value looks low to me.  Typically these are 1,600 volt minimum rated capacitors also.
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Rodger WQ9E
KM1H
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« Reply #2 on: November 04, 2012, 03:21:15 PM »

The 6X5 is notorious about shorting at those voltages. Leave it in for appearance and use SS diodes or go with an 84/6Z4 or better still one of the 5V tubes with a filament dropping resistor. Something that was designed to handle a pair 6F6's with 350V on the plates.

A .006 to .007 1600V or better is the correct buffer value for a simple 260V car radio, Id go for one or a pair of .001 and a .0047 3000V disc.

Carl

 
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WU2D
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« Reply #3 on: November 04, 2012, 07:34:39 PM »

Great tips and the diodes under the tube base is a great trick.

Mike
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WB6NVH
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« Reply #4 on: November 04, 2012, 09:43:02 PM »

A Mallory Vibrapack is a ready-made solution and they were available pre-war. Most used a synchronous vibrator, though, and what capacitors there are inside them probably need replacement.  That's what I am using in such projects.  They show up on eBay from time to time, or at the hamfests out here (where nobody even knows what they are...)

I hate the 6X5 too (as above) yet Motorola used that type in their "Dispatcher" series of taxi radios in 1947 with no issues.  Maybe it was an improved 6X5 by then, but I still don't like them.

You can use a scope to optimize the buffer value when everything is running right.
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Geoff Fors
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« Reply #5 on: November 04, 2012, 09:55:02 PM »

Mike,
     I've never fiddled with a vibrator  before. At approximately what frequency does it cycle at when working properly?  ---Marty, KK4RF---
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KM1H
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« Reply #6 on: November 05, 2012, 05:59:35 PM »

They vary between 90-150Hz (mostly but there are exceptions) but the standard auto radio was 115.

The 6X5 is fine at around 275V DC. There are several internal designs but the GT shape were all after the initial problems that plagued Zenith pre WW2. The JAN versions are the most rugged but all are potential shorters when the voltage is pushed.

I rewire anything with a 6X5 that I own using SS out of sight but leaving the filaments connected and relocating the HV stuff.

Carl

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KA3EKH
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« Reply #7 on: November 07, 2012, 08:51:48 AM »

Not quite as heavy duty as the 6X5 but the 0Z4 is the tube I somehow always think of stuffed into vibrator power supplies, just donít know if that goes back far enough for what youíre doing but it would eliminate all the filament issues.

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kb3ouk
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« Reply #8 on: November 07, 2012, 09:52:20 AM »

This says the 0Z4 goes back to at least 1935.
http://www.radiomuseum.org/tubes/tube_0z4.html
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KA3EKH
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« Reply #9 on: November 07, 2012, 11:00:29 AM »

I remember seeing that tube used in the real old car radios that used octal tubes with vibrator power supplies. Also recall all the old Motorola and GE progress line stuff that had vibrator and later solid state switching supplies and converting that stuff for two meters back in the seventies but back then would not waste time on the vibrator radios considering them to be too old. Back in high school had a Motorola Motrac in my 70 Plymouth and thought I was the man. 
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KM1H
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« Reply #10 on: November 07, 2012, 05:44:12 PM »

The 0Z4 was often the first thing that failed and its not rated for a 350VDC circuit after the filter.
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Patrick J. / KD5OEI
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« Reply #11 on: November 07, 2012, 10:18:57 PM »

0Z4 are usually metal, but I found a little box of glass ones. Unfortunately they do not glow much.
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WU2D
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« Reply #12 on: November 09, 2012, 11:42:02 AM »

Many of the ham built packs I have come across use Selenium RECTUMfriers. Seems that hams wanted to go solid state with small power supplies ASAP. Many were no doubt stolen from old TV chassis.
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« Reply #13 on: November 09, 2012, 06:51:16 PM »

Seleniums in TV's were AC/DC sets, dont know how much B+ they got to but vacuum tubes were used right to the end with transformer sets.
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