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Vertical-deflection

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Hojvaelde

Member
Joined 2005
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.:cool:

Merry Christmas from a big fan.

Benny
 
dhaen

dhaen

Ex-Moderator
Joined 2002
keystrobe.co.uk/
A poor man's 2A3

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

HollowState

Member
Joined 2006
Hojvaelde said:
Argh. Not vertical-deflection but horizontal-deflection (line output/sweep).
Click to expand...
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

Miles Prower

Member
Joined 2005
dolphin-hsl.com
HollowState said:
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.
Click to expand...

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.)
 
H

Hojvaelde

Member
Joined 2005
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
 
Last edited:
HollowState

HollowState

Member
Joined 2006
Miles Prower said:
The main problem here is that the 807/6BG6/6L6 wasn't designed as a horizontal deflection type.
Click to expand...
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.
 
Tubelab_com

Tubelab_com

Member
Joined 2005
tubelab.com
The earliest TV's did use electrostatic deflection. Sometimes the same tube was used for vertical and horizontal sweep. The 6V6 and 6SN7 was common. The Motorola Golden View TV's used 12L6's for both.

The flyback system was designed to create high voltage and horizontal sweep at the same time. This exposed the plate to the flyback voltage pulse. The 807 was the first tube that was repurposed which became the 6BG6 when it got an octal base. Both were rebased 6L6GB's. As far as I can remember the first tube specifically designed for horizontal sweep was the 6BQ6. There might have been others, but the 6BQ6 was certainly the most common. They were already available in large supply at the local trash dump in the early 60's in discarded black and white TV's.

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?
Click to expand...

I have used thr UL84 in guitar amps with the 70 volt line transformer for an OPT. I was getting about 10 watts in P-P until I switched to a mains toroid OPT. Now I get 20 watts and the quality is good enough for HiFi.
 
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