ECF80 and ECF82

[Studio263]

Does anyone know what the important differences between the ECF80 and the ECF82 are? I have an FM tuner here which has one of each in, or at least it is supposed to looking at the diagram on the back. However, at some point in the past the ECF80 has been replaced by and ECF82. The 'real' ECF82 is the FM mixer / oscillator (there's an EF80 RF amplifier before this) but the function of the ECF80 is less clear - possibly the FM AFC reactance stage (F) and audio output cathode follower (C) looking at the rats nest of wiring and components underneath.

The Mullard data books of the era list both types side by side but make no suggestions as to the preferred roles for either. The excellent 'valves and their habits' article in 'Television' (1965 version) says that the 'P' versions were both intended as frequency changers for band I/III TV but get used for lots of other things as well. The only difference they highlight is that the PCF82 can work on a higher voltage supply than the PCF80. The ECF82 isn't mentioned but the ECF80 is listed as the 6.3V version of the PCF80.

Needless to say, the pinning is the same and swapping them over makes no obvious difference. Why make two different valves when one would do?

[GrimJosef]

The ECF82 triode seems to be altogether 'beefier' than the ECF80 one - it has nearly twice the anode dissipation limit (2.7W vs 1.5W) and 50% more cathode current capability (20mA vs 14mA). It also has twice the mu (40 vs 20) and a higher slope (8.5mA/V vs 5.0mA/V) albeit at higher anode voltage and current. The pentode in the '82 is also more highly rated than that in the '80.

Incidentally, has anyone come across a Philips/Mullard datasheet for the ECF82 ? My figures for it came from the Brimar application report.

EDIT: Actually I have just answered my own question. Rummaging through the files has turned up a Philips/Mullard sheet for the 6U8. The figures are much the same as for the Brimar valve.

Cheers,

GJ

[G8HQP Dave]

I suspect that the ECF80 was a European design, while the ECF82 was just a copy of the American 6U8.

[Studio263]

So "the same but different" then? I can't see the differences noted making much of a change to the performance of a practical circuit.

During the early to mid 60s Mullard seemed to have a "thing" for back-filling their range with equivalents to other makers valves but with Mullard style (pro-electron) numbering. Perhaps that's what's going on here, although in this case it is hard to see why they bothered.

[G8HQP Dave]

The ECF82 has more gain, but I think I read somewhere a claim that the ECF80 pentode is more linear. Horses for courses.

[Synchrodyne]

ECF82 was the Pro-Electron code for the American 6U8, released by Tung-Sol in later 1951, closely following the RCA 6X8, these being the first two triode pentodes developed primarily for VHF TV mixer-oscillator service, in response to the move to the higher “40 MHz” receiver IF.

When similar triode-pentodes were needed in Europe c.1953, it appears that some valve makers simply adopted the 6U8, whilst Philips developed its own, namely the ECF80/PCF80. So, the variations amongst these early VHF TV triode-pentodes were probably no more than might be expected when several different makers address the same core requirement. They might not have been directly interchangeable in situ, perhaps requiring differing bias resistors and so on, but functionally they were certainly equivalent.

I don’t know who did the Pro-Electron registration for the 6U8. But as far as I know it was Brimar who did the American registration, namely 9U8, for the PCF82 300 mA series-string version, first developed in Europe. That was not part of the American scene until the later 1950s, as the 9U8A.

The valve makers usually cross-listed, as it were, so for example RCA offered the 6U8 despite having its own 6X8, and Philips/Mullard evidently offered the ECF82/PCF82 as well as its own ECF80/PCF80.

All of these triode-pentodes were slated for use as FM mixer-oscillators, and for miscellaneous other TV and radio receiver functions.

Why a circuit designer would use both the ECF80 and ECF82 in the same unit is a mystery. That implies that of the four functions involved, there was one for which a part of the ECF80 was a “must have” and another for which part of the ECF82 was also a “must have”, with no possibility of cross-substitution. Not impossible, but highly unlikely I think.

Another example of an ECF80 and ECF82 in the same unit came up on another thread here a while back, see: https://www.vintage-radio.net/forum/...d.php?t=135053. The unit in question was a Beam Echo Avantic BM611 AM-FM tuner, which used an ECF82 as FM mixer-oscillator, and an ECF80 pentode as AFC reactance modulator, triode as AF cathode follower.

I wonder if Beam Echo did a mix-and-match from other circuits for this tuner, with no subsequent valve type rationalization. There is at least a circumstantial case that its earlier tuners, the B611 and BM612, used third-party circuitry. But the BM611 is not such an obvious match to any others.

Cheers,

[G6Tanuki]

There was also a 6U8A - not sure if it had a direct European equivalent.

The "A" meaning it had controlled-warmup characteristics on the heater - which also significantly improved the stability when used as a free-running oscillator.

[Synchrodyne]

I think the sequence went something like this:

1951 6U8 released in USA by Tung-Sol
1953 6U8 taken up in Europe as the ECF82, possibly by Telefunken
1953 PCF82 developed in Europe, also possibly by Telefunken
1954 Brimar registered the PCF82 as the 9U8
1954 5U8, with 4.7 V, 600 mA controlled warm-up time heater released in USA as part of the initial set of 600 mA series-string TV valves
1956 6U8A and 9U8A, both with controlled warm-up time heaters, released in USA as part of the second set of series-string TV valves, which included both 450 mA and 300 mA types.
1963 circa European series-string TV valves (300 mA) changed over to controlled warm-up time heaters but apparently without any designation changes. So after this the PCF82/European 9U8 would have had a controlled warm-up time heater.

American 6.3-volt heater valves were generally only reissued in controlled heater warm-up time form if they had 300, 450 or 600 mA heaters and had TV applications. But this actually included quite a bunch of them. Mostly A suffixes were used, unless there was already an A-suffix variant, in which case I think that the B suffix was used.

Getting back to the ECF80 and ECF82 comparison, the ECF80 seems to have been used more than the ECF82 in FM receiver applications.

Relatively common ECF80 applications in FM receivers and tuners included:

Pentode mixer and triode oscillator
Self-oscillating pentode mixer and triode AFC reactance
Pentode IF amplifier or limiter and triode AF cathode follower

Less common were:

Triode mixer and pentode IF amplifier
Grounded grid triode RF amplifier and pentode mixer
Pentode IF amplifier or limiter and triode neon tuning indicator driver (one of a pair)

That radio applications were envisaged as reasonably significant for the ECF80 is indicated by the fact that there was a 100 mA series-string counterpart, namely the UCF80. But there was no “UCF82” as far as I know.


Cheers,

[G8HQP Dave]

Is it possible that the ECF80 pentode was sufficiently similar to the EF80 that it could be used in the same design, while the ECF82 pentode would need some rejigging of component values (and perhaps thoughts about stability)?

[Synchrodyne]

The data do suggest that there was reasonable interchangeability between the EF80 and the ECF80 pentode:



One may imagine in that designing the ECF80, Philips sought to have its pentode be similar to the EF80, within the constraints that applied. In the case of the 6X8, the first of this sub-species of triode-pentode, RCA stated that it was functionally equivalent to the combination of the 6AG5 pentode and one half of the 6J6 double triode. Both of these were WWII miniatures that post-WWII were widely adopted by the American TV setmakers. The 6AG5 had been the de facto standard VHF pentode, although c.1950 there had been later derivatives, the 6BC5 with a moderate improvement and the 6CB6 with a significant improvement.

As best I can determine, Tung-Sol did not make any equivalency claims in respect of its 6U8, rather focussing on other parameters. But RCA also offered the 6U8, and for its version it made exactly the same comparability claims as for the 6X8.

Thus whereas the ECF80 pentode had characteristics that were close to those of the EF80, the ECF82 (6U8) was probably closer to the 6AG5 (EF96), a valve that I think was not much used in Europe.


Cheers,

[PJL]

The uses of the ECF80 in the BM611 does not impact the gain. I would vote for it being simply down to cost.

[Synchrodyne]

If relative cost were a factor, and given that the mixer-oscillator function was likely to have been more critical of valve type than the AF cathode follower and reactance valve function, we might infer that the ECF82 was the costlier of the two valves (at least to Beam Echo). Hence its use in the mixer-oscillator position only, with the cheaper ECF80 in the other position.

Do you know the origins of the Avantic BM611 circuit? For the earlier BM612 particularly, but also the B611, it looks as if Jason circuits were used (e.g. see: http://golbornevintageradio.co.uk/fo...d.php?tid=6846.) The BM612 used the ECF80, but not the ECF82. But the BM611 circuit is not a match for any of the Jason circuits.


Cheers,

[Studio263]

Originally Posted by Synchrodyne

Do you know the origins of the Avantic BM611 circuit?

It has been suggested to me that it is based on a BRC (Thorn / Ferguson) tuner made for export, hence the full FM band coverage (88 > 108MHz ) and the lack of an LW band. Certainly the drafting of the circuit diagram, above chassis views and dial cord layout are pure BRC, as is the distinctive shape of the two combined AM/FM IF transformers. The use of gold coloured cad plate for the chassis is also a BRC favourite of this era. The construction is quite unlike Beam Echo's own products, which feature polished dimpled alloy and matt black painted steel prominently in their internal structures.

Looking through my books I can't find any BRC products which approach the level of sophistication shown in the BM611; all the AM/FM ones I found feature a simple ECC85 (/ UCC85) FM front end and a ratio detector. The distinctive method of drawing the internals of the EBF89 are identical however. I can't imagine BRC messing about doing a small run of a complex product like this just for Beam Echo so they must have sold it themselves somewhere - possibly under the HMV marque.

Something else that suggests that the BM611 is a hasty restyle of something else is that the knobs don't really fit properly. The grub screws are accessible only through holes in an internal metal ring which supports the pointer arrow. In the case of the Beam Echo amplifiers which use the same knobs the holes all line up (e.g. the 'D' in the knob shaft is in the right place for the natural position of the pointer to line up with the scale) but in the BM611 you have to fit the knobs, disengage the metal ring, turn the pointer round to where it makes sense and then try to clip it back on from behind the knob, leaving the grub screw obscured. Its a real faff!

Does anyone know if there is any difference between a BM611 with a black front and one with a copper coloured front? Another forum member kindly shared with me the diagram for the former but my set is the latter and there are quite a few differences, most notably in the values of the resistors used to generate the negative bias voltage. Also, the (copper coloured) fascia graphics seem to suggest that the magic eye works on AM only, which indeed it does - who needs it with AFC? The instruction manual for the black coloured model says that it works on both though - any ideas?

[bikerhifinut]

If the pentode section of ECF80 is an EF80 equivalent, does that mean I could use EF80 and a separate triode in a push pull amplifier circuit that uses ECF80 as pentode first stage into triode concertina phase splitter? The triode section is quite low gain as I remember so I imagine ECC82 would work in the triode position without major circuit value redesign.

Andy

[Synchrodyne]

On the chronology around the Beam Echo Avantic BM611:

The Thorn acquisition of Beam Echo was mentioned in Wireless World (WW) 1959 January p.16. Probably it had happened a few months earlier.

The BM611 tuner was included in the Beam Echo entry in the Audio Fair 1959 catalogue. So it was available by 1959 April.

Hi Fi Year Book (HFYB) 1959 listed the BM612 and B611 tuners, but not the BM611. The cutoff date for HFYB 1959 entries was probably late in 1958.

HFYB 1960, with a probable entry cutoff date of late 1959, listed the BM611, but not the BM612 and B611. Beam Echo as a whole was gone by the time HFYB 1961 was compiled – no mention at all in that issue.

One possible construction is that after Thorn acquired Beam Echo, it decided that it did not like the putative arrangement with Jason on tuner technology and so elected to cancel the existing models and replace them with an in-house design. Perhaps it had to mix-and-match to get near to the kind of performance that the Beam Echo folks wanted, for example replacing a standard ECC85-based front end with a two-valve type. Maybe a readily available front end circuit was based upon an ECF82, and it was not considered worthwhile to do any rationalization work. All speculation of course, but the acquisition by Thorn does seem to have been a nodal point.

The BM612 had been “announced” in Hi-Fi News (HFN) 1958 September, although it had been available before that, being listed in the 1958 (April) Audio Fair catalogue. Anyway, the BM612 had a very short life.

Both the B611 and BM612 were MF-only on the AM side, so the BM611 was consistent with those.


Cheers,

[Synchrodyne]

Originally Posted by bikerhifinut

If the pentode section of ECF80 is an EF80 equivalent, does that mean I could use EF80 and a separate triode in a push pull amplifier circuit that uses ECF80 as pentode first stage into triode concertina phase splitter? The triode section is quite low gain as I remember so I imagine ECC82 would work in the triode position without major circuit value redesign.

"Equivalent" might be a tad strong for the EF80 and ECF80 pentode. Similar, and perhaps directly interchangeable in some circuits might be a more appropriate description. Mullard did note some differences between them when they were employed as video amplifierss, for example.

But I'd guess that they'd be close for an audio voltage amplifier application. As I recall, Jason had found the ECF80 to be reasonable as an audio valve, with no significant hum or microphony problems. Right now I do not recall any specific commentaries on the AF capabilities of the EF80, but I think that they are there to be found.

Cheers,

[Studio263]

The user manual for the Avantic SPA11 (1958 > 1960 according to 'Audio Audio') lists both the BM611 and BM612 as potential matching tuners, along with the STEP11 magnetic cartridge preamplifier and the STEP21 (?) tape head preamplifier. A choice of loudspeakers and an equipment cabinet were also offered. There is no obvious BRC influence in the SPA11 or the STEP11. The circuit diagram is not drawn in the BRC style.

No suggestion is made as to which tuner would be more appropriate, but the '2' models were the more expensive ones (e.g. SPA21).

My BM611 is dated 1959 inside.

[Synchrodyne]

That the BM611 and BM612 were mentioned together indicates that the BM611 had superseded the B611 before the BM612 was withdrawn. Another sequence-of-events possibility is that the B611 was seen as due for replacement with a self-powered model, the Thorn takeover happened before much was done, so a Thorn circuit was used. Then after that, it was decided to stop the BM612 for one reason or another.

I had imagined that the BM611 was the successor to the B611 and was so-named because it was self-powered rather than externally powered. That is, the “M” in the model designation indicated “mains”. And despite its different circuitry, the BM611 may have been seen as delivering about the same overall performance as the B611. The BM612 had an altogether more sophisticated circuit.

There seem to have been two schools of thought when it came to the value of a tuning indicator on an FM tuner equipped with AFC.

One was that the purpose of (relatively mild) AFC was to hold on-tune a receiver that had been precisely tuned in the first place. The latter was preferably achieved by the use of a null-reading tuning indicator, accurate to within say ±5 kHz or better, rather than a conventional peak-reading magic eye, which was a rather crude approach with FM – although much-used nonetheless. As well as specific null-reading devices such as centre-zero meters, twin-neon indicators, and two-bar magic eyes, there were also circuits for obtaining a null reading (sometimes in addition to a signal strength reading) from conventional magic eyes.

The other purpose, usually with relatively strong AFC, was to act not only as a means for holding an on-tune condition, but also to act as automatic fine tuning (AFT), reducing to negligible proportions the residual tuning error from any manual tuning position which put the carrier somewhere within the IF channel. In such cases the view was sometimes taken that a tuning indicator was then superfluous, in that the AFC itself provided more precise tuning than could be achieved manually. In such cases amplified AGC bias was used occasionally. Although a tuning indicator would still be useful showing signal strength.

The Avantic B611 had switched AFC (out for tuning and in for normal operation) that I’d guess was of the fairly strong type. It also had a magic eye tuning indicator that as far as I know was operative on FM as well as on AM.

The BM612 had variable AFC, with a front panel control. I’d guess that it was quite strong at its maximum setting. It also had a twin neon tuning indicator for precise initial FM tuning, and a conventional magic eye for signal strength indication on FM and AM, and tuning indication on AM.


Cheers,