Is this a capacitor?

[TNC]

Just working on an early car-radio power-pack and have discovered this component.

With its red and blue end-caps I am assuming it's a AEG capacitor but the value seems a
little odd to me...E 052/1t ...not sure what that means. 

It reads 860pf but given it is about 65 years ago, I guess it could have arrived at
that value from a long way away!

Grateful for any thoughts on that.

Trevor.        

[ppppenguin]

Not known to me. Any clues from its position in the circuit? With red and blue end caps it's easy to assume that it's polarised. Looks more like a diode than an electrolytic but that's sheer guesswork.

[Crackle]

never seen anything like that.
Does it leak DC current? if you charge it up via an ammeter then switch to more sensitive ranges to end up on the most sensitive range.

Mike

[Murphyv310]

I'm pretty sure it is a selenium diode. It will require a few volts to confirm it conducts only in one direction.

[boater sam]

The position in the circuit will give a big clue.
I would agree it is a diode in all probability as you say it is in the power supply.
Could it be a reverse polarity protector?

[Geordie McBoyne]

Best to check those early rectifiers with a meter and voltage source because the anode was often indicated with a red band or spot rather the modern convention where the cathode is marked red.

Geordie McBoyne.

[ppppenguin]

To reinforce what Trevor said, you can't test it with an ordinary DMM or a cheap universal component tester. Even a diode test range on a DMM is usually limited to 3V which may not be enough to turn it on. An Avo on a range that uses the 15V battery will work. Otherwise I'd suggest a 9V battery, 10K resistor and milliammeter.

[TNC]

Thanks for all your comments.
Some further investigation has revealed the unit has extra circuitry
not shown on the schematic!
I have traced it out at the bottom of the original and attached it as a post.

The component tests out on my multiple tester (that I found after a long search!)
as a diode with the following data - Uf = 1.53v  C = 1.10 Nf

I have also attached a photo of the underside of the unit. This component is hiding
behind the long brown cap part under the chassis rail...which itself sits opposite the
long black cap under the opposite rail.

The extra circuitry comprises two fine cloth covered wires from the transformer - these read
about 4 ohms.
One goes straight to chassis, the other connects to the diode etc as per my drawing.

Is this some sort of safety system as Boater Sam has suggested?

As an aside, what is the purpose of the large gauge wire coils on the input side of
these units?

Thank, Trevor.

[boater sam]

Are the .25uf cap and 200k resistor really shorted out? Seems very unusual.

[Murphyv310]

Are you sure that the diode is drawn correctly? Looks as if it could be a negative supply for bias to me.
The chokes are purely filters, perhaps for interference suppression.