Ideas On Oscillator Circuit

ChrisP58 said:

Most 4 pin relays only have the normally open contact pair (Form A). Self oscillation requires the normally closed contact pair (Form B). Most relays are Form C, which have a common, and both normally open and normally closed contacts, but they will have 5 (or more) pins.
Do you have a part number or a datasheet link for your relay?

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rjenkinsgb said:

If you have a genuine 1960s? vibrator relay, it likely has a common pin for all contacts, a pin for the coil and the other two will be the output contacts to drive the ends of the primary of a centre-tapped transformer.

You should find two pins are connected but with a moderate resistance, a few hundred ohms at a guess? Those will be contact common and coil; it should "run", oscillate, with power applied those.

The other pins go to the transformer, with the centre tap to the coil pin power connection.

Edit - see the schematic here:
View attachment 128640

The vibrator is the part just at the left of the transformer; the armature is the horizontal bar & common contact, the coil & drive contact above with its terminal connected to the cap and choke, then the two power contacts connect to the ends of the transformer primary.
The resistor across the transformer is to limit the voltage spikes as the contacts open.

[That diagram has a version with extra contacts for synchronous rectification - you would presumably use high speed diodes].

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Les Jones said:

Are you sure the battery voltage is not dropping after a few seconds on load ? I think a vaguely remember as a kid I opened some of these vibrators so I could clean the contacts. These were quite common WW2 surplus items in the mid 1950s I think I used to prize open the metal around the paxolin base with large (By today's standards.) side cutters.

Les.

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