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U26

Sensibly equivalent to:
2J2 KY80 R20 U49
See also:
Valves and their Habits - Ediswan First Preference Range Advert - Aspects of design 5: TV EHT Rectifiers (part 1) - Aspects of design 6: TV EHT Rectifiers (part 2) - U25 & U26 Advert
    
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The U26 is a purpose designed EHT rectifier for monochrome television picture tube supplies. The U26 is a plug-in version of the U25.
It would be fed from an EHT overwind on the line output transformer and not a sine wave input. The valve is specified for a peak inverse voltage of 23,500 Volts. With a spike voltage input this suggests 17 - 18 kV for the picture tube. Normal for 15 - 17 inch black and white tubes. The reservoir capacitor would be made from the coatings on the inside and outside of the picture tube and needs to be less than 0.001 µF.
The heater is designed to be driven from the line output transformer and not connected as part of the normal heater chain.
The valve features a bell shaped anode cylinder with a wide separation to the cathode as befits such a high voltage device.
The oxide coated cathode can be seen at the centre of the anode. Note the extra mica support round the centre of the anode.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 68 mm tall.
References: Data-sheet & 1040.

 

Pin Connections
B9A
1
2
3
4
5
6
7
8
9
tc
h,k,s
h
nc
h,k,s
h
h,k,s
nc
h
h,k,s
a

 

Absolute Maximum Operating Conditions
Rectifier
Vh
Ah
mAa
2.0
0.35
0.2
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated January 04, 2022.
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