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Old 25th Sep 2019, 8:16 pm   #21
Mr 1936
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Default Re: Moreton Cheyney

Talk of 19 sets reminds me of a story my Dad told me a only couple of weeks ago. Just after the war at the tender age of 21 he was placed in charge of a REME telecomms workshop. One of their tasks was to repair faulty 19 sets. The method adopted was to first change all the waxed capacitors. This apparently returned over 50% of the sets to full health, the remainder were then subject to more detailed scrutiny !

The workshops were full of "old hands" who spent a lot of time covertly repairing domestic radios, re-plating cigarette lighters etc. Dad decided that he would have to turn a blind eye to all this, being rather outnumbered.
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Old 26th Sep 2019, 12:12 am   #22
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Default Re: Moreton Cheyney

Quote:
Originally Posted by allan View Post
I've added a few more findings which you can take a look at incuding the action of the cams. The DST100 used sets of fixed capacitors to broaden the IF response but moving dust cores is another option. I wonder why the designers didn't just add extra capacitors as it would have been a lot cheaper? Because of general aging their method looks a bit iffy but I'll see if I can sort it out later.
At the time, it may have been that mechanical variable selectivity was seen as a valid alternative to electric methods, at least for professional or semi-professional equipment for which robust and durable mechanisms could be justified. The Moreton Cheney receiver may well have had semi-professional aspirations. As an example, Eddystone used the mechanical method in its 680 receiver, about which Wireless World (WW) said the following in its 1949 June review:

“An unusual feature of this set is that it has a mechanical mechanically operated selectivity system, or as it is sometimes called, bandwidth control. The couplings between primaries and secondaries of the i.f. transformers, and hence the selectivity of the circuits, is varied by change in physical relationship of the coils. The principle is not new ; it may actually have predated the more commonly used electrical systems, but it is never-the-less a perfectly sound one, and moreover, is quite satisfactory as applied to this set.”

The final clause in that commentary definitely has a conditional tone. One may infer that poor mechanical design and/or mechanisms that deteriorated over time would elicit a different opinion.

Eddystone did use electrical variable selectivity, based upon switched IFT tertiary windings, in some of its later models, such as the 880 and 940, but the 830, of the same era, had the mechanical type. Horses for courses perhaps, even within the same design house. On the other hand, the empirical evidence is that electrical variable selectivity, usually with switched tertiary windings, was the dominant approach used in domestic receivers.

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At the end of the day I don't think the extra bandwidth will be of much use because my SDR shows the true width of modern broadcast stations that I can hear to be no more than 14KHz to 15KHz max (+/-7KHz).
There has been quite a bit of discussion of AM transmitted bandwidths on this forum, including the changes over time. There is applicable content in these three threads amongst others:

https://www.vintage-radio.net/forum/...=1#post1072168
https://vintage-radio.net/forum/showthread.php?t=120815
https://www.vintage-radio.net/forum/...ad.php?t=70496

Deliberate and severe restriction of AM transmitted bandwidth is primarily a European idea, dating from the late 1960s/early 1970s. At the time the Moreton Cheney receiver was designed, 10 kHz audio bandwidth was at least a de facto international target for AM broadcasting, and I have one datapoint that suggests that 10 kHz was also promulgated by the CCIR. Some transmitters of the time went to 15 kHz, that group including BBC Brookman’s Park. British wideband AM receiver and tuner practice of the period – and into the 1950s - appeared to be based upon a maximum audio bandwidth of 10 to 12 kHz (20 to 24 kHz IF bandwidth). So with 12 kHz maximum audio bandwidth, the Moreton Cheney receiver was at the upper end of that range.

In apparently having separate bass and treble tone controls of the continuously variable type without switching between the lift and cut functions, the Moreton Cheney was quite avant-garde. Whilst such controls – in passive form - had been available from c.1939 (see: https://www.vintage-radio.net/forum/...55&postcount=3), uptake was fairly slow, and much equipment of the late 1940s had more cumbersome arrangements.


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Old 26th Sep 2019, 11:05 am   #23
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A few comments here... I carried out a few wax condenser experiments over the last few years. I don't think I ever found one that was serviceable. I pass current from a variable HT supply and a resistor.. say 100kohm through the test condenser and measure the volage across the resistor. Most leak badly and do so differently depending on the voltage and many of the things measure something like double their marked value so an 0.1uF would be 200nF or more. There are two or three areas where this and the leakiness matters, and no doubt most Forum members are aware of these but in many cases the leakiness doesn't really matter too much.

Turning to the Moreton Chayney... how old was Charles Miller? I can see a chap with that name born 1922 who appears to have married three times. I suspect the tag boards in the set may have been farmed out to locals.

I found the IFTs, where the variableness is used, needed to be removed and overhauled because the damp had rusted the dust cores in place and the coils were unglued. One had broken ages ago and the other I broke when trying to free it.

Today I started tracing the circuit starting with the pair of 6J5 output valves. The circuit is very strange.. quite possibly because the owner made some changes. The first thing you can see from the pictures is an absence of transformers. The output transformer must have been fitted to the loudspeaker.. sold as an extra. However there are no connections to the anodes of the two 6J5 valves other than a pair of 51K resistors fed by a single 10K from HT. The only output connection to the 6J5s is a 4.7nF capacitor taken to a pin on a rear socket.
The unit I received with the set does have push pull KT66s so my guess is the owner dispensed with the "10 watt.. 2% dist" 6J5s (really?) and fed a low amplitude audio signal from one 6J5 to his own amp.
This makes things even more difficult for me to restore the set. No original circuit diagram...
I suspect the large resistors in the 6J5 anodes are original and were to avoid problems if the speaker with its transformer was not plugged in.

The two ganged pots now look like radio plus gram volume.
The pair near to the chassis corner now look like treble and bass controls.
I'll add more details later as I uncover the obstacles...
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Old 27th Sep 2019, 12:30 am   #24
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It could be that the Moreton Cheney Silver Dragon receiver as originally conceived had a two-piece chassis, with the receiver and the control section on one part, and the power supply and output valves on the other. This was not so unusual for larger units of the time, and for example was an approach used by Armstrong for its EXP125 model and by Dynatron for its Ether Conqueror series. The control section and the power amplifier were not necessarily quasi-independent, either. In at least some of the Armstrong EXP125 iterations, the main feedback loop was returned to a control unit stage via the umbilical cord, so they had to work together.

The WW 1946 October item gave the Silver Knight valve count as 16, excluding the rectifiers. With 14 (including the tuning indicator) on the main chassis, that would suggest that only the pair of output valves were on the output/rectifier chassis, with all other AF valves on the main chassis, which is consistent with what has been identified. It looks as if the main chassis had a phase splitter followed by two triode drivers.

The PSU/KT66 unit that came with the main receiver might or might not be the original, but given the interdependence of the two units in this case (drivers on one chassis, output valves on the other) it seems more likely than not that it was. 10 watts from a pair of triode-strapped KT66s seems reasonable and at the time triode-strapping was the usual way to use these valves in higher quality audio applications, as done by Williamson and Leak for example. (Walker was well ahead of the curve in using distributed loading.) 2% distortion suggests that there might not have been NFB, or not much of it, anyway. Insofar as Osram was actively promoting the KT66 for civilian AF use at the time (possibly with attractive pricing), it would have been a logical choice.

I’d expect the PSU/KT66 unit to include the output transformer, in keeping with normal post-WWII practice, but that said, there were one or two late 1940s units (some Armstrong models for example) that did not have onboard output transformers, but were intended for use with speakers that included transformers.

Anyway, I guess the question is – does the AF side of the unit make more sense if the PSU/KT66 unit is regarded as an integral part of the assembly?


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Old 27th Sep 2019, 12:31 pm   #25
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I haven't studied the amplifier om but it's really heavy.
You can see it here if you scroll down.
http://www.radiomuseum.co.uk/spiralarm.html
Besides the KT66s it has a pair of EF37 valves.
It certainly has two plugs which match the sockets on the receiver and I'm afraid safety was not part of their thinking because HT must be present on exposed plug pins.
When I saw this chassis I thought it was a high power modulator modified for driving a loudspeaker in a secondary role.

The quoted number of valves is puzzling. If there were two models Dragon and Knight maybe mine is the latter and has less valves? It could have been a misunderstanding though "including" rather than "excluding" rectifiers?
Certainly the mains transformer and HT rectifiers need a chassis but mine has a socket for one rectifier, two KT66s and two EF37s which pushes up the count to 18 plus a rectifier and there seems to be a lot of transformers/chokes on my chassis. The KT66 in p-p triode AB1 mode is quoted at 2% and probably 10W at around 300 volts so that fits much better than the humble 6J5.

One explanation is that the owner bought only the receiver and cobbled together a surplus chassis to do the job. Time to examine it more closely.

Incidentally I found something a little odd. One of the 6J5 valves on the radio chassis has its (twisted) heater connections brought out separately to one of the rear sockets whilst the other valves share the same heater circuit (in screened cable).
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Old 27th Sep 2019, 1:39 pm   #26
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OK folks.. I now seem to have, not only the only surviving Moreton Chayney receiver, but the only surviving Moreton Chayney amplifier.
https://www.radiomuseum.co.uk/mca.html
This raises yet more questions.
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Old 27th Sep 2019, 2:00 pm   #27
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Congratulations
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Old 27th Sep 2019, 4:46 pm   #28
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The two-variable-capacitors - one large, one small - approach makes eminent sense in a receiver with wide frequency-coverage, it does at least mean that if you've got 'enough' capacitance-swing to nicely cover the MW broadcast-band you can avoid the 'tunes over several MHz in a few degrees of tuning-knob rotation' problem on the higher frequencies.
The RCA AR88 uses the same approach though there the 'little and large' capacitors are mounted on a common spindle.

I hadn't noticed the double-tunedness of the IFTs - fo you know what the IF is? I'm guessing 450-470KHz but am aware that there were plenty of receivers produced that had non-standard IFs like 560KHz or something around 1.6-1.7MHz.
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Old 27th Sep 2019, 5:41 pm   #29
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I just measured the IF coils as the transformer is detached for repair of the variableness control (in its rest position) and they are 877uH and 891uH with trimmers measuring around 110pF with my Peak test meter, so if you allow say 25pF for the coil's self capacity it works out around 465KHz which is nice to know.
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Old 28th Sep 2019, 12:17 am   #30
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The puzzle is getting more complicated! With tetrode-connected KT66s in what was a high quality unit, I’d half expect to find another KT66 acting as voltage stabilizer for the output valve screen-grid supplies. Re the two EF37s on the amplifier chassis, one might be the driver and the other the phase splitter. Or perhaps both are drivers, with the phase splitter back in the tuner/control unit section.

Some of the abundance of valves on the main chassis could be accounted for by what might be called the supplementary functions, namely infinite impedance detector for the TRF mode, AFC, and volume expansion. Each would probably account for at least one triode or pentode beyond the basic circuit requirements. I should not be too surprised if there were a separate oscillator valve, and some form of amplified AGC, either using an IF sidechain or a DC amplifier.

The 465 kHz IF was I think a fairly standard UK number in the pre-Copenhagen Plan era. (Post-Copenhagen, BREMA recommended 470 and 422 kHz.)


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Old 28th Sep 2019, 11:34 am   #31
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Do I see a mains transformer winding that is no longer connected? If this is 4V AC then maybe a pair of PX4's (B4 base) have been replaced with KT66?

Are the transformer windings still intact?
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Old 28th Sep 2019, 12:09 pm   #32
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That might be possible om because I can see that those ceramic valveholders have been fitted using securing rings although the chassis is drilled for standard holder fixing screws. I'll check to see if there's evidence of those being used..

I found extra info on the company including that they sold an 8 valve amplifier and they had premises in Bilston in early 1947 then later that year had moved to Gaol Road.
All speculation but I wonder if their business was foundering so stopped production and moved unsold stock to 52a Gaol Road?

One ad mentions bandspread on the Dragon so I'm thinking of moving back to the Silver Knight.

The main transformer looks pretty good but the other chokes etc may have been attacked by damp. At least the copper wires will have a decent gauge so may be OK. I'm tackling the receiver first.

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Old 29th Sep 2019, 8:00 pm   #33
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This has been an absorbing thread to follow- maybe this is a classic exercise in market-sector choice and mission-creep!

At this time, there would have been many de-mobbed servicemen (servicepeople?...) with electronics training who would have been used to working with high-grade kit with comprehensive facilities. Perhaps someone enthused by the idea of going into business post-war would have found it difficult to compromise the urge to offer something top-notch, while prospective purchasers would shy away from a necessarily very expensive product with an unknown pedigree. The punters have always been conscious of the "good name" brand-awareness thing that marketing folk exploit for better or worse. If this tuner hadn't reached quite so high, the company might have been more successful- they could still have offered something with an RF stage but say, one IF stage and a two-position "fidelity/clarity" bandwidth choice that would have justifiably claimed to be ahead of the pack but not been quite so off-puttingly expensive- the sort of approach that was successful with the Quad II tuner later on.

Sometimes designers need the much-lambasted bean-counters leaning over them, there's a successful compromise somewhere in there...

Good luck with what looks to be a challenging task so far.
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Old 30th Sep 2019, 8:43 am   #34
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Quote:
Originally Posted by Mr 1936 View Post
Talk of 19 sets reminds me of a story my Dad told me a only couple of weeks ago. Just after the war at the tender age of 21 he was placed in charge of a REME telecomms workshop. One of their tasks was to repair faulty 19 sets. The method adopted was to first change all the waxed capacitors. This apparently returned over 50% of the sets to full health, the remainder were then subject to more detailed scrutiny !
After the war, times were hard and no-one was in a position to waste time or money. The fact that the method adopted re wax capacitors was to change them all on sight is a measure of it being the best method to deal with them. Having wasted time replacing them piece meal, testing and measuring them, I adopted the 'change en mass' strategy half way through my very first restoration in '77. I still don't understand why people try to 'work with them', changing only the very obviously faulty ones when they are all functionally imperfect/faulty in some way or other. And don't forget, the war ended over 70 years ago, waxies do not improve with age!
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Old 30th Sep 2019, 8:56 am   #35
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I agree, Steve. To me, all waxies are 'change on sight', along with the dreaded Hunts 'Moldseals', and a few other makes/types of component prone to causing trouble. After all I doubt if the designers and makers of the equipment in which they were used ever expected it, or those capacitors, to last 60, 70 years or more!
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Old 30th Sep 2019, 11:30 am   #36
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I guess I agree with all those comments.
My own approach is to establish if a receiver is a viable proposition before swapping everything in sight. If it's a rare equipment I'll stuff the old parts to preserve it's looks, but initially I'll repair any critical bits then attempt to power it up. If all goes well, before any smoke appears I'll be able to judge if the thing is worth doing properly.
This particular set is tricky as the circuit diagram isn't available so I'm now tracing everything. Hopefully the Sprague condensers are going to be better than the wax ones. The Spragues are basically 0.1uF with wax examples for most of the 0.05uF and 0.01uF.
https://www.radiomuseum.co.uk/Morton.html
Maybe I'll show the parts list today or tomorrow. Around 75 resistors and 75 condensers at the last count.
Then there's the amplifier

Of course times haven't changed much. Electrolytic capacitors pushed to smaller and smaller physical sizes can now be very unreliable.
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Old 3rd Oct 2019, 11:17 am   #37
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I finally found the death knell of the company in 1948. It seems the last advertisement for the receiver was actually from the liquidators trying to help creditors by shifting unsold stock.
http://www.radiomuseum.co.uk/Morton.html
Presumably, just as they were moving to bigger premises the market was flooded with government surplus receivers.
I still haven't discovered the guys themselves.. presumably Messrs Moreton and Cheyney?
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Old 3rd Oct 2019, 12:58 pm   #38
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Keep looking Allan, it's a very interesting story.
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Old 3rd Oct 2019, 4:01 pm   #39
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I might have cracked it Steve?
I found an Annie Cheyney married Albert Moreton and they lived in Stafford.
Their daughter married a guy called Tarry. Tarry was the company secretary who called for the creditors meeting.
That joins up Moreton, Cheyney, Tarry and Stafford.
Whether it was Albert or Albert's son James born 5th Aug 1902 I don't know yet.
Maybe just a weird coincidence..
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Old 4th Oct 2019, 1:23 am   #40
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Excellent sleuthing! So Moreton Cheney (MC) lasted about three years.

Previously I was thinking that the original MC output used triode-strapped KT66s. But the WW 1946 November item did say triodes, and applying Occam’s Razor, I’d say that that meant actual triodes and not triode-strapped tetrodes. Thus it could well have had PX4s or PX25s as original equipment.

Also from reading through again carefully the available material, it appears that MC itself did not claim that its product was in fact a communications receiver. Rather it claimed communications receiver sensitivity. In that regard the WW 1946 November item was slightly misleading.

A good communications receiver of the time would have been of the single-conversion, 2 x RF and 2 or 3 x IF type with an IF in the 450 kHz range. However, the second RF stage was used primarily to improve pre-mixer selectivity rather than sensitivity, so it is plausible that a 1 x RF, 2 or 3 x IF type receiver would provide a similar sensitivity. (Marconi published a set of curves that showed that all else being equal, the 2nd RF stage made little difference to sensitivity, whereas there was a big change in going from no RF stage to one.) Some communications receivers allowed an AF bandwidth of 7 or 8 kHz in the widest IF position, although 5 or 6 kHz may have been more common. Either way this was short of the 10 kHz which was a reasonable minimum for high quality MF reception. Also, communications receivers would not always have had low distortion AM demodulators or low distortion AGC systems, either. Thus, if one regards communications and high-quality as two different performance vectors, then the MC receiver pretty much went towards the top end of the high quality vector, but just part way along the communications vector. The two vectors were not irreconcilable, but doing a full job along both surely came at a cost.

For customers who wanted a communications receiver, then a WWII surplus unit probably made the most sense, and this was also likely the best solution for SW broadcast DX’ing as distinct from listening to programme content. As turretslug has suggested, for those whose main requirement was high quality MF reception, simpler and lower cost solutions were available. What the MC receiver offered was a combination of high quality MF reception with very good SW reception for programme content listening, and probably quite good DX’ing performance with its narrowest bandwidth. That was likely quite a small market in the UK. And MC as a very small enterprise may not have been in a position to develop the export market, which would have required the appointment of agents in target countries/regions. One could say that its chances for success were minimal from the start.

MC was not alone. For example the Peerless receiver range, available approximately 1946 through 1949, seemed to have suffered a similar fate over. But the established manufacturers Armstrong and Dynatron were successful with high quality MF-plus-good SW broadcast receivers, both in the late 1940s and through the 1950s.

Below the MC, priced at £52.00, was the Armstrong EXP125, at £33.60, which had a two-piece chassis. This was introduced as Armstrong’s top-of-the-line model, sitting above a procession of lesser models progressively introduced after WWII. Evidently it built upon the reputation established by the pre-WWII AW125PP. The radio section of the EXP125 was of the 3-gang, 1 RF, 2 IF type with 3 positions of variable selectivity, bandwidths unknown, but I’d expect at least 10 kHz AF in the wide position. Initially this was an export-oriented model, but it was also included in Armstrong’s domestic listings. It went through various iterations, including the addition of a bandspread variant (BS125), with a final rework in 1959 that lasted until c.1961. Armstrong started what was a slow transition from radio/radiogram chassis maker to hi-fi component maker in 1954.

Above the MC was the Dynatron Ether Conqueror T69A/LF59 combination, the chassis pair alone priced at £84.00. Dynatron was well-established in the “carriage trade” sector, and its specialty was fine cabinet work for complete radiograms. Thus it had its own market niche in which it could command high prices. The radio section of the T69A tuner/control unit was of the 3-gang, 1 RF, 2 IF type with 4 positions of variable selectivity, 10 kHz AF at the widest position. At I think the T69C iteration, it became 4-gang with a bandpass circuit somewhere in the front end, I think maybe at the interstage. The T69/LF59 was succeeded by the T99/LF612 in 1951, with the bandspread T139/LF613 arriving in 1954 and lasting until c.1959. Dynatron had headed in the hi-fi components direction in 1955, but the change of ownership eventually took it downmarket.

We could reasonably assume that those who wanted a receiver in this class and didn’t have to ask the price would buy a Dynatron. For the others, the question might be asked as to whether the 55% higher price of the MC as compared with the Armstrong EXP125 brought a matching quantum of realizable extra performance, perhaps along with a better build quality. And if so, whether this was worth the risk of buying from a new, and probably very small organization, whose after-sales support was an unknown variable. It appears that there were precious few who were game enough to try it.

By way of comparison, the Eddystone 680 communications receiver (of the single-conversion 2 x RF, 2 x IF type, with a maximum AF bandwidth of around 7 kHz) was advertised in mid-1949 at £85.00, with no purchase tax.


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