The UY85 is a half wave rectifier and would be used on small universal (AC/DC) mains appliances. The heater chain would draw 100 mA and this was to enable the small number of valves used in a broadcast radio receiver to be run without a large dropper (ballast) resister.

The UY85 can work into a maximum reservoir capacitance of 100 µF, as protection a series resistance of 100 Ohms minimum is required.

The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 57 mm tall.

References: Datasheet & ¹⁰⁴⁰. Type UY85 was first introduced^¶ in 1954.

 
Pin Connections

B9A	1	2	3	4	5	6	7	8	9
	-	-	k	h	h	-	-	-	a

 
Absolute Maximum Operating Conditions^¶

Rectifier	Vh	Ah	Va	mAa
	38	0.1	250	110

Thanks to Frank Philipse for supplying the above PDF datasheet

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