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Synchrodyne 22nd Aug 2019 3:02 am

Valve Items - Philips/Mullard Rimlock-to-Noval Transition
2 Attachment(s)
This is more or less an extension of the old “Valve Questions” thread,

Therein was discussed inter alia some aspects of Philips transition to the noval base from its own Rimlock form.

To recap, Philips in 1949 adopted the noval base for most of its “World Series” of TV valves, the EF80 and ECL80 being early releases in that series. There was technical justification for the 9-pin base. For example, in the case of the EF80, it enable the use of two cathode pinouts whilst retaining a separate pinout for the internal screen. In contrast, Mazda’s comparable (or in some ways better) 6F1, on the Rimlock base, required that the internal screen and the suppressor grid share a pinout in order to allow two cathode pinouts. (The preceding 6F13, also on the Rimlock base, had a single cathode pinout and separate internal screen and suppressor grid pinouts.)

With radio valves, the first big “wave” of noval releases, at least as far as Europe was concerned, arrived c.1952 with those intended specifically for FM-AM receivers, such as the ECH81 and EABC80. However, the transition had started in an apparently small way 1949. The EBF80 had a noval base out of necessity, and the unique enneode (renamed, perhaps misnamed as a nonode by Mullard) was changed from the Rimlock EQ40 to the noval EQ80 before major production began.

But there was another facet to the Philips transition to the noval base, and that related to its Australian valve manufacturing activities. There it would have appeared to have skipped the Rimlock phase (although that needs to be confirmed), instead going direct to a noval-based radio receiving base range in 1949. The initial announcement of this Australian-manufactured range, on 1949 November 29, was recorded in an item in the magazine Australian Radio and Television News 1950 January, excerpt attached:

Attachment 188702

The valves concerned were as follows:

6AN7 triode hexode, being the American designation for the ECH80, which was the ECH42 on a noval base.

6M5 output pentode, being the American designation for the EL80, which was the EL41 on a noval base.

6BD7 double-diode triode, being the American designation for the EBC81, the EBC41 on a noval base.

6N8 double-diode pentode, being the American designation for the EBF80.

(Evidently American RTMA valve designations were preferred in Australia, even though the Pro-Electron type were much more informative.)

Philips referred to these valves as being part of the “Innoval” range. I am not aware that it used that descriptor in Europe; I do not recall seeing it used in connection with for example the “World Series” TV valves.

I am not sure if the initial Innoval range were the first novals to be made in Australia. By the time of their release, AWV was already making B7G valves (6BA6, etc.) in Australia, but it might not yet have been making any novals, although it was probably importing some from RCA USA. One of AWVs’ early noval productions was the 6AE8 triode heptode in 1950; this was in fact the Osram X79, for which AWV did the American registration. In the absence of a miniature triode heptode from RCA, AWV had to look to its UK principal for what was evidently an important valve type in the Australian market.

Whether Mullard ever used the “Innoval” term is not clear, but it was absent from a Mullard advertisement for the initial four Innoval valves in Australia Radio and Television News 1950 May:

Attachment 188703

In fact, Mullard’s use of the term “9-Pin” for these valves rather than simply “noval” might be construed as a desire not to connect with “Innoval”, even indirectly.

As best I can determine, valves such as the 6AN7 and 6M5, replicates of existing Rimlock issues, were never offered in Europe. Rather the Rimlocks remained in place until their FM-AM era replacements, the ECH81 and EL84 were released.

The EBC81 (6BD7) looks as if it were held back in Europe until c.1955, about the same time as the then-new EF89 was released. Rather the Rimlock EBC41 was used until then, although somewhat displaced by the EABC80 as FM-AM receivers displaced the AM-only type. Evidence is provided by the example of the Pye FenMan II radio receiver, released in 1955 but probably the outcome of a 1954 design study, which had an EBC41 in an otherwise all-noval line-up. It also had an EABC80. Two AF triodes were anyway needed, and the use of the EBC41 both delivered the second triode and allowed the use of delayed AGC on AM. One imagines that had the EBC81 been available from UK/European production at the time, it would have been used in place of the EBC41. (The corresponding HFT111 AM-FM tuner avoided the EBC41 as not needing any AF triodes, the EABC80 triode was strapped to provide a 4th diode.)

The Philips/Mullard transition from Rimlock to noval was not a simple exercise, with different timelines in different geographies.


joebog1 22nd Aug 2019 8:36 am

Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition
I must admit I am very young at this trade. I am 67.
I dont even know, nor have I seen a "Rimlock" valve.
Very often there are valves with designations such as

I then load to find out what they really are.
( MOSTLY I look at the alternatives)
I have never been to New Zealand, even though its only "over the ditch". I do know that about 1/2 the RAF migrated to NZ after the war, and designed some excellent radios and TV's before we went colour TV in the 70's. ( We never had TV at home)
In the whole of my career and education, Australia has only ever used USA designations for valves.
Noval base is immediately recognised as 9 pin miniature.
Octal is of course original 8 pin with spigot
Miniature is 7 pin miniature, which I am 3/4 sure made huge headway in Australian manufacture during the 1950's.
Loctal I know from African military radio gear that was sold into the surplus market in the late 1950's and early 1960's.
Also, I have discovered that the Australian military used many types of loctal valves in the early plywood jet aeroplanes.
These are plentiful here, BUT still use American numbers, not some hidden code of secret numbers and letters that mean ( after 60 years of working with valves) NOTHING.

I dont mean to be disrespectful, but surely there is a common thread here??. Would it be possible to list BOTH type numbers in posts?


paulsherwin 22nd Aug 2019 9:54 am

Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition
Australian electronics was largely dominated by American rather than European practice after WW2, perhaps influenced by the huge US military presence during the Pacific war.

Restoration73 22nd Aug 2019 10:13 am

Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition
B8A types were used in new designs even when the replacement B9A types became
available. This applied to UK and European designs.
There was also a transition from a metal base to all glass construction.

kalee20 22nd Aug 2019 10:17 am

Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition
Interesting thread, Synchrodyne.

I'm also intrigued by the initial press cutting describing the new base from Philips (Innoval = International Noval maybe?) but in the advert for specific valves they used Mullard branding!

turretslug 22nd Aug 2019 10:21 am

Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition
In the case of the EBC41, perhaps the 6AT6/EBC90/DH77 had already achieved popularity in the UK market- a valve pitched as having a triode primarily intended as AF amp would not need anything more than the by-then well established 7-pin base and the double-diode-sharing-cathode-with-triode-AF-amp technique had been an established and successful part of AM receiver design since the mid-'30s. Thus, a Rimlock/Noval DDT was probably seen as low in the priority list. Maybe Pye could get a good deal on EBC41s and their existing radio and TV production meant economic bulk purchasing/holding of Rimlock/B8a sockets anyway. The EBC41 does have an internal screen and an inherently skirted socket adds to the screening integrity- maybe Pye felt that this was worthwhile with what was pitched as a high-quality, high-fidelity set, though there's probably not much in it.

G8HQP Dave 22nd Aug 2019 11:14 am

Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition

Originally Posted by joebog1
I dont mean to be disrespectful, but surely there is a common thread here??. Would it be possible to list BOTH type numbers in posts?

Yes it would sometimes be helpful to have the informative European name used alongside the almost meaningless US name for valves. How are we supposed to know that 6AL5 is a pair of diodes, 6AK5 is a UHF pentode and 6AM5 is an audio output pentode? Much better to know that these are EB91, EF95 and EL91 respectively - this even tells you which base they use (miniature, B7G).

julie_m 22nd Aug 2019 3:04 pm

Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition
I hope this might help someone:

Handy Guide to Mullard Type Numbers (almost certainly incomplete)

First letter: Heater voltage or semiconductor material.
A = 4V or Germanium
B = Silicon
C = 200mA
D = 1.4V
E = 6.3V
G = 5V
H = 150mA
K = 2V
O = cold cathode
P = 300mA
U = 100mA

Second and subsequent letters: Electrode structure(s).
A = signal diode
B = two signal diodes sharing a cathode
C = signal triode or AF transistor
D = power triode or AF transistor
F = signal pentode or RF transistor
H = hexode or heptode requiring separate oscillator
K = octode or heptode used as self-oscillating mixer
L = power pentode or RF transistor
M = indicator tube
Q = enneode
T = thyratron or SCR
Y = rectifier diode
Z = two rectifier diodes sharing a cathode, or zener diode

Tens: Package (only for valves).
0 = Continental side contact
2 = Loctal
3 = International Octal
4 = 8-pin Rimlock
7 = wire-ended
8 = 9-pin miniature
9 = 7-pin miniature

Usually 0 for the first valve of a type, then increased as variants were introduced. Often, an odd number on a pentode indicates variable µ.

So for example we have DM71 (a wire-ended indicator tube with a 1.4V heater), UCC85 (a 9-pin dual triode for 100mA series heater wiring), GZ34 (an International Octal full-wave rectifier with a 5V heater), EABC80 (a 9-pin multi-way valve with a triode, a separate diode and two more diodes sharing the triode cathode for 6.3V parallel heater wiring) and BD139 (a silicon audio power transistor).

The system isn't perfect ("EB91" actually has separate cathodes; some valves had multi-rated heaters, e.g. 6V3 / 300mA, and could be used in a series or parallel arrangement, but this is not obvious; and it totally lost the plot on the numeric portion with semiconductors) but it's at least an attempt to be sort of vaguely logical.

TonyDuell 22nd Aug 2019 5:08 pm

Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition
Some additions :

I seem to remember that 'B' as a first letter was used on valves too. Was it '180mA'?
Other first letters were also used. I seem to remember reading 'Y' was perhaps 450mA? Was 'F' 12.6V? They are all very uncommon though.

For further letters,

E : signal tetrode
(L could also be power tetrode I think)
N : thyratron (e.g. EN91)
X : gasfilled fullwave rectifier
Z : vacuum fullwave rectifier

First digit 6 was also wire-ended (DF64, DL64, etc)

At some point the numbers changed from 2 digits to 3 digits. Valves with 3 digits have a few changes in the coding :

First letter G : miscellaneous heater voltages (the GY501 EHT rectifier does not have a 5V heater).

First digit 2 : B10B base (e.g. PFL200)
First digit 5 : B9D (Magnoval) nase (e.g PL504)

kalee20 22nd Aug 2019 6:05 pm

Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition
Yes, 'X' and 'Y' were used for 450mA and 600mA (can't remember which way round though).

'7' as first figure is not always wire-ended, sometimes it is Loctal (eg EM71 - one wonders why this was not designated EM21?)

And '5' existed as first figure, B9G (eg EF50). But it was not a common base, though the sheer quantity of EF50's produced rather made up for it!

'B' as second latter didn't always mean diodes sharing the same cathode, EB91 has for instance separate cathodes (there is also an EAA91!!). In the EABC80 it's a moot point whether the 'B' refers to the two FM diodes (one completely isolated, one sharing the triode cathode) and the 'A' the AM diode (which also shares the triode cathode), or the 'A' diode being the isolated diode and the 'B' diodes the (unequal) ones sharing the triode cathode. But I shan't be losing sleep over this...

It's a good system.

julie_m 22nd Aug 2019 6:55 pm

Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition
Thanks for filling in the ones I missed :)

This might even be a candidate for the forum mod team to stickify, once the collective memories have been safely gathered in :)

Maarten 22nd Aug 2019 7:15 pm

Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition
You might want to remove the A and B for germanium and silicium if this is going to be sticky, since they have never existed in this coding system. From the top of my head, in the new transistor coding system, the letters A, B, C and R are used and even there don't indicate germanium or silicium but rather the bandgap range.

It could be argued that the older letter O for transistors is part of the tube numbering system.

I would have to look it up, but I think 450mA and 600mA are L (not Y) and X. Not sure in which order. Both mainly used for television valves for the 110V market.

Nuvistor 22nd Aug 2019 9:13 pm

Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition

Originally Posted by joebog1 (Post 1170287)
These are plentiful here, BUT still use American numbers, not some hidden code of secret numbers and letters that mean ( after 60 years of working with valves) NOTHING.

Hi Joe,
I have read similar things in 1950/60 USA radio magazines.

The European system gives much more information. The USA designated numbers generally mean nothing to me, the odd one perhaps but not many whereas I can quickly identify with European numbers.

It’s what you get used to using.

joebog1 22nd Aug 2019 11:59 pm

Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition
2 Attachment(s)
This is a scan from one of my data books. It might help everybody a little.
I think I may have confused the issue somewhat when I didn't understand the European system.
Apart from a few audio valves ECC8*, KT66, KT88 I have never worked on anything containing European numbered valves. Hence I never bothered to learn the system.


Synchrodyne 23rd Aug 2019 6:32 am

Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition
Re the double-diode triode case, Philips included the EBC41 in its initial Rimlock range, announced in 1946. It would appear that Philips wanted to have all of the core domestic receiving valves in Rimlock form, even though some would have fitted on the B7G base. The initial Rimlock range also included the EB41 double diode.

The EBC41 was probably available from UK production (Mullard) at about the same time as the American B7G-based 6AT6, as such from Brimar and probably Cossor, and as the DH77 from Osram. It seems likely that the EBC41 and 6AT6 established themselves in parallel in UK setmaker practice as the changeover was made to miniature valves of one kind or another.

Philips initial noval-based radio receiving valve range of 1949 also included a double-diode triode, namely the 6BD7/EBC81. Again it would appear that Philips preferred putting this valve type on a noval base, even though it could instead simply have picked the EBC90 (6AT6) from its industrial range. One could infer that it preferred to have an internally screened double-diode triode for receiving applications (as with the EBC41) and that as far as reasonably possible, it now wanted to standardize on the noval base.

Of the four novals in this initial release, the available evidence is that all four (6AN7/ECH80, 6N8/EBF80, 6BD7/ECH81 and 6M5/EL80) were made available in Australia right away, but only the EBF80, which perforce had no Rimlock counterpart, was offered in UK/Europe. Given that the ECH42, EBC41 and EL41 were established in UK/Europe, Philips elected to delay the changeover for that region. Possibly in 1949 it had the ECH81 and EL84 in view, and did not see any benefit from an intermediate change in those two categories. It may also have had the EABC80 in view, and saw that as largely displacing the EBC41 as receivers moved from AM-only to FM-AM configuration. Of course, it could have been a ploy to extend somewhat the “frontline” life of its Rimlock range. An odd facet is that the key Rimlocks eventually received American registrations and type numbers, but this did not happen until later in 1955. What that was about I do not know; perhaps for replacement supply in American designation-oriented markets into which Rimlock-equipped receivers had nonetheless found their way.

An early addition to the noval range was the 6BH5/EF80, essentially a noval version of the Rimlock EF41, and initially released for Australia but not for UK/Europe. Philips’ initial thinking was that the EF41 would be displaced by the EF85 in FM-AM applications. Apparently it was not the best option for the IF gain stage(s), so there was a rethink that resulted in the EF89/6DA6 c.1955 as the direct and improved successor to the EF41. The arrival of the EF89 meant that there was now a nearly complete set of novals for FM/AM and AM-only applications in UK/Europe, with the EBC41, now much less used, as the only outlier. Thus it was time to release the EBC81 in UK/Europe in order to complete the noval series.

Pye was in the Mullard Rimlock camp when it came to its first wave of miniature valve domestic receivers, and thus used the EBC41 amongst others. Thus it was logical that when it (unusually) required a double-diode triode for its FenMan II FM-AM receiver, it would use the EBC41. On the other hand, given that the FenMan II otherwise used noval valves, it is also reasonable to assume that it would have used the EBC81 had it been available from Mullard UK when the receiver was designed.

Notwithstanding the precedent of the EB41, Philips did not issue a noval-based double-diode. Rather it drew the EB91/6AL5 B7G-based double diode from its industrial series into its domestic radio and TV receiving range.

Re Australian post-WWII practice, notwithstanding the dominance of American influence, there were also UK/European elements. These included some use, possibly quite extensive, of the triode-hexode/heptode AM frequency changer rather than the American pentagrid. The valves concerned, e.g. ECH80/6AN7, 6AE7/X79 and ECH81/6AJ8 were all of European origin. Another was the use of the double-diode pentode, such as the 6N8/EBF80. The use of noval-based HF pentodes, such as the EF89/6DA6 was also European, as the American miniature HF pentodes all used the B7G base.

The triode-hexode/heptode case suggests that the Australian setmakers did not all share the American “love affair” with the (relatively noisy) 6BE6. Possibly there was greater inclusion of shortwave bands in Australian-made receivers (bearing in mind that SW was used for some Australian domestic broadcasting back then), and that was where the 6BE6 shortcomings were more likely to show up. But to be fair, some American setmakers avoided using the 6BE6 by other means that were facilitated by the need to offer FM-AM receivers. GE, having developed the 12AT7 double-triode for use as an FM and TV frequency changer, used it in its radio receivers, where it was used not only for FM, but also for AM, on which band one triode served as oscillator, with the FM 1st IF stage, often a 6AU6, serving as AM mixer. So effectively GE used a triode pentode AM frequency changer. Zenith also adopted the 12AT7 as FM frequency changer, and then used it as such (both sections) for AM. RCA used the 6X8 triode pentode as both FM and AM frequency changer. The 6X8 was developed as a VHF TV frequency changer, but was also designed from the start to be suitable for FM-AM applications. RCA triode-strapped the pentode mixer section on FM, but not on AM.

New Zealand was much more of a mix in terms of valve types used, and during the 1950s and 1960s one saw equipment with American-numbered (and usually American-type) valves and European-numbered valves, including Rimlocks. I recall seeing more European than American valve numbers, but whether that reflected the actual split I don’t know. But a typical radio receiver of the later 1950s/early 1960s from the Waihi factory (which supplied several brands) was ECH81, EF89, EBC81, EL84, EZ80. There was some use of American-numbered European-type valves. AWA made a wideband AM tuner (MW-only) to match the RCA UK Orthophonic hi-fi equipment for which it was the NZ agent. This had a 6BY7 (EF85) RF amplifier, 6AJ8 (ECH81) frequency changer and 6DA6 (EF89) IF amplifier. (The use of the EF85 as an AM RF amplifier was I think unusual, but then Marconi used two of them in its NS702/2207C Atalanta HF receiver).

Generally, I have found that to make sense of the receiving valve ranges that were offered in different parts, and they way they were used, one has to drill down quite a way to find otherwise obscure reasons, or at least plausible rationalizations, not always technical.


Synchrodyne 30th Aug 2019 5:32 am

Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition
5 Attachment(s)
Here is another magazine item about the release of the Philips Innoval valve range in Australia, in this case from “Radio and Hobbies” 1950 January:

Attachment 189106

There was recognition by Philips that it was using the standard noval base, but it claimed to be using a special sealing method, not requiring very high temperatures, that achieved greater accuracy and rigidity of the internal structure. One could deduce that Philips saw that feature as justifying the “Innoval” name.

Philips also stated: “Since the miniature 7-pin base is inadequate for certain types of valve, the adoption of the standard 9-pin Noval base appears to be a very logical step.”

When it introduced the Rimlock series, Philips stated that the 8-pin base covered the majority of domestic receiving applications, including the triode hexode/heptode frequency changer, which the B7G base did not. It also said that for the very valves few that required 9 pins, the established B9G base would be used. The more complex valves required for emerging TV and FM applications soon showed that 9 pins would be required quite often, not just occasionally.

The “Innoval for everything domestic receiving” approach contrasted with the American approach, which was to use the noval base only for miniature valves that required 8 or 9 pins (and occasionally, for those that required a slightly larger bulb than was standard for the B7G type). The B7G base was used for miniature valve that did not require more than 7 pins.

(In the immediate post-WWII era, it was evidently the American plan was that where the B7G base was inadequate, the octal base, with a top-cap as needed, would be used. Hence in that short pre-noval period there were some new octal small-signal releases, such as the 6S8 triple-diode triode and 6SB7Y higher performance pentagrid, which were supplanted by corresponding noval issues within a couple of years.)

As noted upthread, Philips did depart from the “Innoval for everything domestic receiving” approach in the case of the double-diode, where the B7G EB91/6AL5 was pulled into the range. (And there were some later B7G deviations, such as the EF97, EF98 and EH90.)

Here is an early Philips advertisement for its Innoval range:

Attachment 189107

And a magazine item, from Radio and Hobbies 1952 March:

Attachment 189108

This announced three additions to the Innoval range, namely the 6AD8 double-diode pentode (different to the 6N8/EBF80), the 6V4 rectifier (EZ80) and the 6BH5 (EF80) RF pentode.

The 6AD8 may have been an Australia-only issue. The pentode part had low gm (1.1 mA/V) and the valve was said to be suitable for use in reflex receivers. From that I should infer that low gm was preferable when reflexing – perhaps for adequate stability when one valve is simultaneously amplifying IF and AF?

The EZ80 was registered as the 6V4 on 1949 April 19. So this was another Philips noval valve that was evidently held back for several years in the UK and Europe, in favour of the EZ40.

The 6BH5, with a gm of 2.2 mA/V, was said to have been configured to meet expected performance characteristics in Australia. But the 6BH5/EF80 was none other than the EF41 on a noval base, retaining the internal suppressor grid-to-cathode connection. So that was a bit of exaggeration on Philips’ part. Also, by then, AWV was offering the 6BA6 with a gm closer to 4 mA/V. So maybe Philips was endeavouring to head-off any questions as to why its new RF pentode was not similarly configured.

AWV appears to have had a major influence in the Australian market. This item from Radio and Hobbies 1949 September covers its 1949-50 domestic receiving range, inclusive of several B7G miniatures, but no novals:

Attachment 189109

This advertisement from Radio and Hobbies 1952 September covers the addition of the 6BV7 and 6AE8, both on the noval base. As all of the other valves listed therein were of the B7G type, the two featured may have been AWV’s first domestic receiving novals.

Attachment 189110

The 6BV7 double-diode output pentode was an AWV own-design. So by 1952 third quarter, three distinct noval double-diode pentodes were available from Australian manufacture, namely the 6N8, 6AD8 and 6BV7.

As already noted, the 6AE8 was the Osram X79. An interesting point was that AWV chose to register it to obtain an American designation, something that it had not done with its predecessor, the X61M. The 6AE8/X79 looks to have been a very competent triode heptode. Its conversion conductance was similar to that of the ECH81 (6AJ8). It differed from the latter in having an internal connection between the triode grid and the heptode injection grid, whereas the ECH81 had an external connection. How it compared noise-wise I don’t know, but I’d guess that it was similar. I have the impression that in Australia, the 6AE8 was widely used through to the end of the valve era, whereas in the UK, the ECH81 more-or-less swept all before it, including the X79.

The X79 itself was simply a rebased X78, which being on a B7G base, required a common pinout for its cathode and one side of the heater, a rather awkward arrangement, and a consequence of Osram’s having chosen the B7G rather than say the Rimlock base for its initial miniature receiving range. Its primary “77” series frequency changer was the X77 (later X727)/6BE6 pentagrid, but it also needed a triode heptode to address the UK setmaker majority preference, hence the X78 in the short pre-noval period.


Synchrodyne 30th Aug 2019 5:46 am

Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition
5 Attachment(s)
.pdf versions of the attachments from the previous posting for better readability.

Maarten 30th Aug 2019 1:14 pm

Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition
The special sealing method might be fritting the button to the tubing as was usual in rimlock valves. This was abandoned after the first generation noval valves.

Looking at the 1951 ad, this indeed seems to be the case. I've got a few of those in my collection, EABC80 a.o.

turretslug 30th Aug 2019 11:23 pm

Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition
The Rimlock valve types always struck me as having notably neat, short and precise interlinking connections between base and electrode assembly, whereas 7- and 9-pin miniatures generally seem to have longer interconnects with more in the way of interlink bends and swan-necks- but this latter observation could make some sense in the context of a structure that necessarily attained much higher temperature during base-to-envelope welding (as opposed to the use of frit which could be described as analogous to soldering in the way that the joint is made with a lower-melting point material!) and needed to be more resistant to heat distortion and have more "give". I'm sure there has been the occasional mention/picture on here in the past of B9a types with frit-jointed bases that sound like the early types mentioned above.

Comparing the construction of, say, an ECH42 to the previous-generation ECH35, they are something of a revelation in precision and miniaturisation and must have represented considerable investment in production jigs and tooling.

joebog1 31st Aug 2019 1:33 am

Re: Valve Items - Philips/Mullard Rimlock-to-Noval Transition
For those that want to read a very interesting publication, here is a copy of
AWV/Radiotron from 1936 to 1966. In every issue any new valve releases were listed in there own section, Very often these included application notes and design hints for using the new releases. It also contains lots of information on early AWV transistors.

I wonder, could somebody please post a pic of a Rimlock valve?.
I have no idea what they are, or more likely its a difference in naming.

Thanks in advance

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