The U191 is a television efficiency diode. The function of the device is to enable the stored energy of the line scan coils to be returned to the supply rail during flyback.

The valve is rated at 5,000 Volts (PIV) and a peak current of 600 mA. The valve is unusual in that the top cap is taken to the cathode. This means a 5,000 volt heater cathode insulation. See also PY301

The wide glass tube envelope is 28 mm in diameter and excluding the IO base pins it is 73 mm tall.

References: Datasheet & ¹⁰⁴⁰.

 
Pin Connections

IO	1	2	3	4	5	6	7	8	tc
	-	ic	ic	-	a	-	h	h	k

 
Absolute Maximum Operating Conditions^¶

Diode	Vh	Ah	mAa
	19.0	0.3	120

Thanks to Frank Philipse for supplying the above PDF datasheet

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