The Christmas 2018 High Voltage quiz part one.

[Heatercathodeshort]

The final batch of part two.

[ms660]

Part two number 1

EA50?

Lawrence.

[ms660]

Part two.

Number 6....DY87 ?

Number 7....R20 (or equiv.) ?

Number 8....1X2B ?

Number 9....DY802 ?

Lawrence.

[high_vacuum_house]

Part 2 number 5

Wire ended neon lamp with a wire tucked underneath it? Appears to have no top pip for the lead out wire?

Final batch No.4

E/DY87/807 I have a NOS one but the anode bell has fallen off its perch!!


Christopher Capener

[ms660]

Part two.

Number 2....U37 ?

Number 3....EY51 ?

Number 4....U25 ?

Number 5....Rogue.

Lawrence.

[ms660]

Originally Posted by ms660

Part two number 1

EA50?

Lawrence.

Needless to say that's not an EHT rectifier.

Lawrence.

[Studio263]

As an aside, here's something you don't see every day - three 1DK1s used in an EHT multiplier found in various late 60s Sony sets (this example is from a TV-900UET). They are absolutely tiny!

[Heatercathodeshort]

Well thanks again for your interest. Laurence apparently had the saddest Christmas because he managed to get all of them correct.

Chris at HVHouse should be working for MI6 as he managed to detect my cleverly disguised Neon stabilizer tube.

OK, here are the answers.

1 Our old favorite the 'Television Diode' in it's military guise. The EA50 Mullard version has a 6.3v heater, the D1 Mazda a 4V. Originally employed as a pre war vision detector but often discovered post war as a vision clipper in interference limiter circuits.

2 The tiny MOV U37. It made it's first appearance in the GEC BT1091 [1949] and was their answer to Mullard's EY51 that beat it to the post by about a year. It has a 1.4v filament.

3 The 6.3V wire ended Mullard EY51, probably the most well known EHT rectifier of all time. First seen in the Autumn of 1948 employed in the Pye B18T series. It's last duty was a grand exit as focus rectifier in the Philips dual standard G6 colour receiver from 1967 to 1971.

4 The Mazda U25/GEC U47. Mazda's 2V heater version of the EY51 but. nothing like as reliable. It often failed with internal flashing, purple glow and low emission causing the picture to 'balloon' on high brightness scenes.

5 Yes Chris, a very badly disguised 'anode' connection on a neon stabilizer tube.

6 Mullard EY86, the uprated B9A based version of the EY51. A reliable valve.

7 Mazda's U26, the 2V heater version of the EY86. Better than the wire ended U25 but still suffered from the same old problems.

8 Difficult one here. It's the Brimar R19/1X2B. B9A based with 1.25V heater.
Low emission was a common complaint. Used in KB receivers from the mid fifties including the Royal Star PVP20. It has an identical appearance to the R20 that is a direct equivalent for the Mazda U26. The Mullard version is the DY80.

9 Lastly the Mullard DY802. The 20kv uprated version of the DY86/87. Used in the final versions of the large screen monochrome receivers. It's large bell anode gives it away. A pointless so called 'upgrade' introducing an XRay hazard with little if any improvement in the picture. It's mechanical internals were very weak for a Mullard valve resulting in a detached anode bell with the filament hanging out of the cathode tube.

Yes Tim, an amazing bit of valve technology. The EY51's fitted in the early Philips projection tripler cans were special miniature versions similar to those Sony versions.

There are of course a few more EHT rectifiers used in UK manufactured receivers but I could not find them! The B7G R10 comes to mind and the very rare B4 based/screw anode Philips type employed in the pre war Philips projection receiver. This was withdrawn from RadioOlympia in 1937 due to repeated CRT failure. I believe it had MAINS DERIVED 25KV doubler arrangement... What fun!! When I discover them I will post a couple of pics.

Thanks to all that found this of interest and those who had a go.

All the best of health for 2019. Regards, John