The U153 (almost = PY81) was specifically built as an efficiency diode for television line scan and the design dates to the early 1950s. Considerable energy is fed to the line deflection coils and this has to dissipate during flyback. The efficiency diode channels this energy back to the supply rail smoothing capacitors for use on the next line scan.

The rectifier is specified as having a peak inverse voltage rating of 4,500 Volts, and a peak current rating of 450 mA. No voltage drop is quoted so the dissipation can not be given.

The thin glass tube envelope is 19 mm in diameter and, excluding the B9A base pins, is 71 mm tall.

References: Datasheet & ³⁰⁰². Type U153 was first introduced^¶ in 1953.

 
Pin Connections

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

 
Absolute Maximum Operating Conditions^¶

Rectifier	Vh	Ah	Vg	mAa
	17	0.3	-1	150

Thanks to Frank Philipse for supplying the above PDF datasheet