Vertical-deflection

[Hojvaelde]

Hi

We are 3 tubes listeners who each have built a amplifier based on vertical-deflection tubes.
We had an argument about which tube that was the oldest / first vertical-deflection tube.
Since we could not figure it out, we decided to ask the right place and we believe it is here.

Merry Christmas from a big fan.

Benny

[Wavebourn]

6V6? EL84?

[Hojvaelde]

Originally Posted by Hojvaelde

Hi

We are 3 tubes listeners who each have built a amplifier based on vertical-deflection tubes.
We had an argument about which tube that was the oldest / first vertical-deflection tube.

Argh. Not vertical-deflection but horizontal-deflection (line output/sweep). Mine amplifier is 6bg6 based.

My mistake, sorry.

Benny

[Rod Coleman]

EL36 may be a contender - introduced in 1940

EL36 @ The National Valve Museum

[artosalo]

The PL36 was designed as a line timebase output valve for television receivers.
The design dates to the 1950s,

PL36 @ The National Valve Museum

[dhaen]

Actually some vertical deflection valves such as the PL84 and EL86 (which differ only in heater voltage) have low very Rp if run in triode mode. I've often wondered about using them in an SE parafeed arrangement using an off-the-shelf choke and a low cost 70/100-volt audio line transformer. Has anyone tried this?

[HollowState]

Originally Posted by Hojvaelde

Argh. Not vertical-deflection but horizontal-deflection (line output/sweep).

The very earliest televisions had small screens from 5 to 7 inches. They used electrostatic deflection for which direct coupled 6SN7 or 12SN7's were popular. Early electromagnetic deflection employing yoke coils mostly used a 6BG6 making that a good early choice. Dumont used an 807. Sometimes a 6CB5. As a teenager I used to work on these old sets at my after-school job and some I found at the curbs (and dragged home) that were discarded in front of people's houses.

[Miles Prower]

Originally Posted by HollowState

The very earliest televisions had small screens from 5 to 7 inches. They used electrostatic deflection for which direct coupled 6SN7 or 12SN7's were popular. Early electromagnetic deflection employing yoke coils mostly used a 6BG6 making that a good early choice. Dumont used an 807. Sometimes a 6CB5. As a teenager I used to work on these old sets at my after-school job and some I found at the curbs (and dragged home) that were discarded in front of people's houses.

The main problem here is that the 807/6BG6/6L6 wasn't designed as a horizontal deflection type. It started out as the metal envelop 6L6 -- an audio final. It morphed into the 807 for RF duty, having a glass envelop, plate top cap connection and the then standard five pin base for higher voltage operation for more RF output.

Then it morphed again, reappearing as the 6BG6 -- an 807 with an Octal base that served as a TV HD final, but not really suitable for that, as the cathodes are quite a bit finer (6.3V @ 0.9A heater) than what you see with the true TV HD finals, with their thick cathodes and power hungry heaters to go along with high plate currents at low Vpk's.

CRT screen sizes quickly became too much for an 807 to handle as a HD final. These HD finals weren't even considered for audio since you can't run 'em as Class A amps without severe red plating, though quite a few do sound quite good run in PP, Class AB. (Though rated like a 6V6 (Pd= 12W, nominal) a PP pair of Class AB1 6BQ6s can provide ~40W easily and sound as good as 6V6s, and if really pushed, up to 70W of audio power.)

[Hojvaelde]

Hm.

Looking at 6BG6G vs. EL36 vs. EL38. EL36 looks out to a much more modern design.
Similarly, both 6BG6G and EL36 deliver more than 40 watts in PP and Class B and EL36 are somewhat smaller than 6BG6G.

Thanks for the explanation Miles. That explains a lot.

Regards

Benny

[HollowState]

Originally Posted by Miles Prower

The main problem here is that the 807/6BG6/6L6 wasn't designed as a horizontal deflection type.

Miles, there is no "problem". The original question was what was the oldest tubes used. Forget about the etiology of them. These were the tubes that were used back in the day. For better or for worse. And they worked pretty well in that service. If you take the time to look up old schematics, that's all you'll see being used. Proper designed sweep tubes didn't come along until the demands of large screen B&W CRTs and color made them necessary.