Does anyone have a source for the 6 pin vibrators used in the mid 30's farm sets? Can anyone give some tips on how to repair them?

The common trouble with vibrators is that the points get stuck together or pitted. The first thing to try is to smack the unit squarely against a flat surface, striking the flat top of the unit. Don't smack too hard, but make it a fairly sharp blow. You may also try moderately smacking the sides firmly against the surface (table, floor, etc.). Try not to dent the can. If this does not free things up, you can try all of the below. I wrote a lot, so there's a bit to read. In the worst case, the armature may have actually cracked or broken off. The armature is a flat piece of spring steel. These units are not too expensive, though. They range in the $20 area.

Antique Electronic Supply carries a line of 3 and 4 pin solid state vibrators, but not the 6 pin versions. However, they do state that they do have an assortment of new-old stock vibrators of many types. Ask them if they have your's. They are found on the web at www.tubesandmore.com. They do not state anything about the old stock vibrators on their site. It says so in their catologue.

3 and 4 pin vibrators often put the vibrator field coil in series with one half of the transformer primary. Whenever the points for that winding closed, they shorted out the field coil and connected the transformer winding directly to the current source. By doing so, the magnetic field collapsed in the field coil, and the armature then fell back in the other direction, opening that set of points and closing the other set to electrify the other side of the transformer primary. Since the first set of points was now open, current flowed through the field coil again, which pulled the armature back the other way, opening the second set of points and then closing the first set again. The process repeats itself over and over again from 50 to 150 times, depending on the frequency of the vibrator.

Now, with a 6 pin vibrator you may be looking at two designs, depending on your radio. There is the synchronous design. You will know that you have this design if your radio lacks any other form of rectifier (tube, or selenium, though selenium was seldom used in these earlier radios). You will also see in a schematic for your radio, that there are points for both the primary and secondary of the power transformer. Three of the pins on the vibrator are used to perform the previously listed function for 3 and 4 pin vibrators. There are two other sets of points that are linked to the first set so that they are synchronized with eachother. These two other sets of points open and close exactly at the same time (in theory) as the first set, but they are connected to the high voltage secondary of the transformer, which is split into two halves with a center tap just like the primary. The center tap is connected to B- usually, and the two outer leads of the transformer are connected to the two outer points in the vibrator. The two inner points for each set of points (2 sets) are connected to the armature, and connect alternately with each side of the transformer secondary. Since they are synchronized with the primary winding points, every time a primary set of points closes, the corresponding secondary points close and connect the proper phase of the secondary to B+. At the very moment that a set of points closes on the primary, a positive voltage is induced in one of the secondary windings, which is sent through the corresponding closed point on the secondary. As soon as the primary set of points opens, the current reverses in the transformer secondary (induction does this....pulsating DC on one side causes alternating current on the other), but since the secondary set of points for this side of the secondary also open up, the radio does not see this reversal of current. The points on the other side of the synchronized armature for both the primary and secondary corresponding, close, and the process continues for that side. In this way a direct current can be delivered to the radio without a rectifier tube, saving filament current. The secondary points, which are synchronized to the primary, catch the voltage at just the right time so that it is always flowing one way. I must add that depending on vibrator design and how the points are synchronized, you may find the B current polarity as listed above, or perhaps in reverse (B+ at transformer center tap and B- at vibrator points).

Now, the other type of 6 pin vibrator you may have will be used in a radio with a rectifier tube. It will have only two sets of points on one armature like the 3 and 4 pin models, but the field coil will not ever be connected in series with any transformer winding. It will receive its current directly from the current source, and will have its own set of adjustable points (with a set screw) that opens and closes with armature movement to turn on and off the field coil at the above mentioned frequencies.

Sorry for the long story about vibrator operation, but I thought you'd like to know how it works before you open it up. You can open your's up by prying open the crimp along the base. Remove the aluminum shell. If the armature (flat piece of spring steel) is still in shape--hasn't cracked in half, check to see that none of the points have stuck together. You may clean them gently with an extremely fine sand paper. Do not bend anything. If the field coil has its own set of points, they should be closed when the vibrator is at rest. The armature pole piece (piece of steel rivveted to top of armature) should lie just to the side of the field coil pole piece so that when the field coil is energized, it pulls the armature towards it. The two sets of points diametrically opposed to eachother, or four if your's is a synchornous model, should not be closed when the vibrator is at rest. They should have a very small air gap, perhaps the thickness of an index card. If this is not so, bend what needs to be bent until all falls into adjustment. You may test the vibrator out of the can by tracing the wiring to the field coil. Connect a 6 volt DC source to this wiring. Hold the vibrator gently so as to not dampen vibration, and watch its operation. Listen as well. It should start up smoothly and hum evenly. It should be able to start up at about 5 volts. If it cannot start up at exactly 6 volts, then the points controlling the field coil must be adjusted. If the armature has cracked in half, unless you're really good with spring steel and rivvets, you are better off purchasing a new one. I rebuilt one once with a new piece of spring steel, by removing the points off the old one, but it is not really worth your time and you will not necessarily have a reliable vibrator.

If you cannot find a replacement vibrator of either the mechanical variety or the solid state variety, there are circuits available for building solid state units. The unit, built on a small circuit board found at Radio Shack, may be assembled in the old can. Someone on here likely knows a circuit, or I can search for one for you on the web.

Thomas

:Does anyone have a source for the 6 pin vibrators used in the mid 30's farm sets? Can anyone give some tips on how to repair them?

Hi Tom,
Thanks for all the info. Will let you know how I make out. Thanks again for your time. :The common trouble with vibrators is that the points get stuck together or pitted. The first thing to try is to smack the unit squarely against a flat surface, striking the flat top of the unit. Don't smack too hard, but make it a fairly sharp blow. You may also try moderately smacking the sides firmly against the surface (table, floor, etc.). Try not to dent the can. If this does not free things up, you can try all of the below. I wrote a lot, so there's a bit to read. In the worst case, the armature may have actually cracked or broken off. The armature is a flat piece of spring steel. These units are not too expensive, though. They range in the $20 area.
:
:Antique Electronic Supply carries a line of 3 and 4 pin solid state vibrators, but not the 6 pin versions. However, they do state that they do have an assortment of new-old stock vibrators of many types. Ask them if they have your's. They are found on the web at www.tubesandmore.com. They do not state anything about the old stock vibrators on their site. It says so in their catologue.
:
:3 and 4 pin vibrators often put the vibrator field coil in series with one half of the transformer primary. Whenever the points for that winding closed, they shorted out the field coil and connected the transformer winding directly to the current source. By doing so, the magnetic field collapsed in the field coil, and the armature then fell back in the other direction, opening that set of points and closing the other set to electrify the other side of the transformer primary. Since the first set of points was now open, current flowed through the field coil again, which pulled the armature back the other way, opening the second set of points and then closing the first set again. The process repeats itself over and over again from 50 to 150 times, depending on the frequency of the vibrator.
:
:Now, with a 6 pin vibrator you may be looking at two designs, depending on your radio. There is the synchronous design. You will know that you have this design if your radio lacks any other form of rectifier (tube, or selenium, though selenium was seldom used in these earlier radios). You will also see in a schematic for your radio, that there are points for both the primary and secondary of the power transformer. Three of the pins on the vibrator are used to perform the previously listed function for 3 and 4 pin vibrators. There are two other sets of points that are linked to the first set so that they are synchronized with eachother. These two other sets of points open and close exactly at the same time (in theory) as the first set, but they are connected to the high voltage secondary of the transformer, which is split into two halves with a center tap just like the primary. The center tap is connected to B- usually, and the two outer leads of the transformer are connected to the two outer points in the vibrator. The two inner points for each set of points (2 sets) are connected to the armature, and connect alternately with each side of the transformer secondary. Since they are synchronized with the primary winding points, every time a primary set of points closes, the corresponding secondary points close and connect the proper phase of the secondary to B+. At the very moment that a set of points closes on the primary, a positive voltage is induced in one of the secondary windings, which is sent through the corresponding closed point on the secondary. As soon as the primary set of points opens, the current reverses in the transformer secondary (induction does this....pulsating DC on one side causes alternating current on the other), but since the secondary set of points for this side of the secondary also open up, the radio does not see this reversal of current. The points on the other side of the synchronized armature for both the primary and secondary corresponding, close, and the process continues for that side. In this way a direct current can be delivered to the radio without a rectifier tube, saving filament current. The secondary points, which are synchronized to the primary, catch the voltage at just the right time so that it is always flowing one way. I must add that depending on vibrator design and how the points are synchronized, you may find the B current polarity as listed above, or perhaps in reverse (B+ at transformer center tap and B- at vibrator points).
:
:Now, the other type of 6 pin vibrator you may have will be used in a radio with a rectifier tube. It will have only two sets of points on one armature like the 3 and 4 pin models, but the field coil will not ever be connected in series with any transformer winding. It will receive its current directly from the current source, and will have its own set of adjustable points (with a set screw) that opens and closes with armature movement to turn on and off the field coil at the above mentioned frequencies.
:
:Sorry for the long story about vibrator operation, but I thought you'd like to know how it works before you open it up. You can open your's up by prying open the crimp along the base. Remove the aluminum shell. If the armature (flat piece of spring steel) is still in shape--hasn't cracked in half, check to see that none of the points have stuck together. You may clean them gently with an extremely fine sand paper. Do not bend anything. If the field coil has its own set of points, they should be closed when the vibrator is at rest. The armature pole piece (piece of steel rivveted to top of armature) should lie just to the side of the field coil pole piece so that when the field coil is energized, it pulls the armature towards it. The two sets of points diametrically opposed to eachother, or four if your's is a synchornous model, should not be closed when the vibrator is at rest. They should have a very small air gap, perhaps the thickness of an index card. If this is not so, bend what needs to be bent until all falls into adjustment. You may test the vibrator out of the can by tracing the wiring to the field coil. Connect a 6 volt DC source to this wiring. Hold the vibrator gently so as to not dampen vibration, and watch its operation. Listen as well. It should start up smoothly and hum evenly. It should be able to start up at about 5 volts. If it cannot start up at exactly 6 volts, then the points controlling the field coil must be adjusted. If the armature has cracked in half, unless you're really good with spring steel and rivvets, you are better off purchasing a new one. I rebuilt one once with a new piece of spring steel, by removing the points off the old one, but it is not really worth your time and you will not necessarily have a reliable vibrator.
:
:If you cannot find a replacement vibrator of either the mechanical variety or the solid state variety, there are circuits available for building solid state units. The unit, built on a small circuit board found at Radio Shack, may be assembled in the old can. Someone on here likely knows a circuit, or I can search for one for you on the web.
:
:Thomas
:
:
:
::Does anyone have a source for the 6 pin vibrators used in the mid 30's farm sets? Can anyone give some tips on how to repair them?

http://www.antiqueautomobileradio.com/vibratorsF.htm

They sell solid state vibrator replacements, and one of them on their page appears to be 6 pins.

:Does anyone have a source for the 6 pin vibrators used in the mid 30's farm sets? Can anyone give some tips on how to repair them?