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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 29th Nov 2022, 10:12 pm   #21
Synchrodyne
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Default Re: Combined power-pentode and double-diodes?

The 6BV7 double diode output pentode appears to have been an AWV own development in the absence of a suitable valve from either RCA or Osram. Given that it could have gone either the “EBF” or “EBL” route, it is reasonable to assume that its choice of “EBL” was considered and deliberate, and not just happenstance.

Possibly to some extent it wanted to do differently to Philips, who had added the 6N7 (EBF80) to its “Innoval” range late 1950/early 1951, and followed it with the 6AD8 early in 1952. In the latter, the pentode was configured for used in the reflex mode as both an IF and an AF amplifier.

In respect of the 6BV7, AWV did make the observation: “The location of the diodes in the output valve allows a very convenient layout of the conventional 4 valve straight or reflexed receiver and enables higher i-f gain to be obtained without excessive regeneration, or without neutralizing, than is possible when the diodes are located in the i-f amplifier valve.”

(Neutralization in EAF and EBF type valves was discussed by Langford-Smith, pp.1066,7 in the Classic edition.)

Doing differently to Philips per se was probably not the only motivation, though. For example, just previously AWV had introduced the 6AE7 (Osram X79) triode-heptode frequency changer to run alongside its standard 6BE6. Evidently it was feeling the heat of the competition, Philips having introduced the 6AN7 (ECH80) as one of its first Innovals late 1949/early 1950. Clearly, there was a significant part of the market that saw the triode hexode/heptode as superior to the pentagrid frequency changer, so that in this case AWV had to follow Philips and offer this type. (The 6AE8 was probably a bit better than the 6AN7, though.)


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Old 30th Nov 2022, 11:01 am   #22
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Default Re: Combined power-pentode and double-diodes?

Quite recently I remember reading a write up in the Wireless World about the E/UCH21 and it's release from Eindhoven. They stated that it was going to be the start of limiting the types of domestic valves in broadcast receivers to a few simple types.
Circuits were given for it's use as frequency changer, another for I.F. amp, L.F. amp with a E/UBL21 in short superhets as a detector/output valve and a UY21 rectifier.

They also put the later B8A E/UCH42 to all sorts of use in both radio and TV receivers. As with all Philips products they worked outstandingly well. I can't remember the WW edition but I'm sure someone may have better indexing than me! John.
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Old 30th Nov 2022, 12:00 pm   #23
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Default Re: Combined power-pentode and double-diodes?

Quote:
Originally Posted by G6Tanuki View Post
Even in the Octal days, I'm amused to see that the basic EL33 pentode took only 0.9A@6.3V heater but its dual-diode-pentode sibling the EBL31 needed a massive 1.5A@6.3V for its heater!

Needing 0.6A@6.3V additional heater-power just to drive a couple of signal-frequency diodes seems to be getting a bit louche and bordering on the profligate!

What was going on there?
That strikes me, too- a modest, run-of-the-mill AF power capability in return for more heating power than the brawny KT66 of the same era is puzzling. Most AM-orientated signal diodes seemed to have been miniscule slivers of metal at one end or the other of the cathode tube, so can't have needed much share of the emissive power requirement. Compare with the 6.3V 0.15A of the 6AQ6 double-diode/signal triode, whose triode was of the EC90/half-ECC82 class. Even granting each diode a third of the cathode heating power suggests only 50mA each. The all-round spec. of the EBL21 is sufficiently close to that of the EBL31 to suggest that it might have consisted of a very similar basic electrode assembly but with a more efficient cathode coating (0.8A vs. 1.5A).

One topic that crops up periodically is the scarcity of EBL31s that are compatible, i.e. sufficiently short to fit in the Ekco A22- it seems that most of those available have been converted from side-contact EBL1s, the give-aways being the added-on (and incompatibly high) International Octal base and 3/8" rather than 1/4" top-cap. It struck me that the EBL21 could be used in these sets with a socket change, and with the bonus of reduced heater current/internal heat. Not strict originality, I guess it depends on whether having a going concern or concours example is the priority.

I believe that the ECH21 was originally designed as a B9G type, but was then decanted into the 8-pin base, hence the cathode-to-spigot connection quirk. Maybe it was felt that it was better to have a valve whose socket was compatible with existing International Octal chassis punching for production convenience- the B9G format may have been an advance over existing types in terms of short internal connections and glass base, but being of even larger diameter than the already large International Octal seems curiously retrograde.
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Old 30th Nov 2022, 12:29 pm   #24
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Default Re: Combined power-pentode and double-diodes?

In my Mullard data book, the EBL1 heater current is given as 1.2A but the EBL31 is specified to be 1.5A.

I have pencilled 1.2A against the EBL31 entry, presumably based on a measurement I made years ago. Can anyone confirm this?

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Old 30th Nov 2022, 12:49 pm   #25
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Default Re: Combined power-pentode and double-diodes?

Attached are two examples of Mullard datasheets in which 1.2 A for the EBL31 is specified.

Perhaps the 1.5 A was a mistake, but it could also be that soon after the release of this valve type the heater was changed/improved. There are more examples of such changes in heater consumption.
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Old 30th Nov 2022, 1:05 pm   #26
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Default Re: Combined power-pentode and double-diodes?

Radio Valve Data 8th edition (Iliffe) EBL31 heater current also given as 1.2 Amps.

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Old 30th Nov 2022, 5:04 pm   #27
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Default Re: Combined power-pentode and double-diodes?

Quote:
Originally Posted by Heatercathodeshort View Post
Quite recently I remember reading a write up in the Wireless World about the E/UCH21 and it's release from Eindhoven. They stated that it was going to be the start of limiting the types of domestic valves in broadcast receivers to a few simple types.
Circuits were given for it's use as frequency changer, another for I.F. amp, L.F. amp with a E/UBL21 in short superhets as a detector/output valve and a UY21 rectifier.

They also put the later B8A E/UCH42 to all sorts of use in both radio and TV receivers. As with all Philips products they worked outstandingly well. I can't remember the WW edition but I'm sure someone may have better indexing than me! John.
Not W.W. but a 1949 Philips publication for the EBL21/ECH21 etc etc:

https://www.rsp-italy.it/Electronics...20-%201949.pdf

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Old 3rd Dec 2022, 3:09 am   #28
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Default Re: Combined power-pentode and double-diodes?

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Originally Posted by jjl View Post
The 2 off ECH21 plus EBL21 or U equivalent circuit was a war-time Philips Eindhoven development intended to save cost; more info here. Tesla and Philips seemed to have some sort of commercial relationship at the time, hence Tesla's use of the circuit during WWII and continuing into the late '50s.
I don't think Tesla and Philips had a commercial relationship at that time, but one of the more important factories that were nationalised and made part of the Tesla conglomerate, was the Philips radio factory in Prague.
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Old 3rd Dec 2022, 1:49 pm   #29
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Default Re: Combined power-pentode and double-diodes?

That is interesting. I don't have the Philips publication and can only think it was picked up by the WW.
I have been going through piles of them recently to a view of salvaging most of them. John.
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Old 5th Dec 2022, 4:14 pm   #30
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Default Re: Combined power-pentode and double-diodes?

Does anyone know what was the point with the EBL71? Are there other identical tube types (same base, specification) with the same identification schemes?
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Old 5th Dec 2022, 4:49 pm   #31
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Default Re: Combined power-pentode and double-diodes?

Radiomuseum says EBL71 is similar [though not necessarily a direct equivalent] to EBL21 and Marconi DN143.

I guess they were just trying to recreate the EBL31 on the Loctal base?
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Old 10th Dec 2022, 12:57 pm   #32
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Default Re: Combined power-pentode and double-diodes?

I think the EBL21, EBL31 and EBL71 are more like successors/recreations of the EBL1. Or maybe the EBL31 was the octal version of the EBL1, with EBL21 and EBL71 being successors.

I don't know the purpose of the EBL71 either, it seems to be an identical copy of the EBL21 but assigned a new number by Lorenz. Maybe they didn't want customers to know they were using a, by then, seemingly outdated tube.

Last edited by Maarten; 10th Dec 2022 at 1:03 pm.
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Old 11th Dec 2022, 8:50 am   #33
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Default Re: Combined power-pentode and double-diodes?

The EM71 M.E. was another rarely seen valve. If you discover one it usually has very good emission. It must have been part of the 70 series. J.
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Old 11th Dec 2022, 2:34 pm   #34
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Default Re: Combined power-pentode and double-diodes?

I discovered they had an ECH71 as well, so in the late 1940's or early 1950's Lorenz copied and possibly improved the early 1940's Philips line up and added at least a magic eye to it. Not a bad idea, if it weren't for noval valves being introduced around the same time.
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Old 11th Dec 2022, 5:38 pm   #35
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Default Re: Combined power-pentode and double-diodes?

If you want a really strange 'hybrid' valve, look at the EFM1 - a tuning indicator built into the same bottle as an audio variable μ pentode.

http://www.r-type.org/exhib/aaa0982.htm

What were they thinking??

It even had a follow-on!

https://www.radiomuseum.org/tubes/tube_efm11.html

using the strange German base with the pins non-synnetrically arranged round the central spigot.

That there were no Octal/Loctal/B8/B9 successors shows that such things failed to capture the imagination of radio-designers.
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