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Old 5th Jul 2022, 2:16 pm   #1
PJL
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Default Dynatron mid 30's 'tuner'

I picked up the radio chassis from majex45 and as suspected it is from a radiogram being a top of the range Dynatron (model 1114? similar to Ether Empress). No power supply and missing the exotic power amplifier but I have a PSU I could connect it up to. It has 9 mid-30's B5 and B7 valves, one empty octal socket, a flying lead with B7 plug to connect to another module, and an interesting dial with rotating paper scale.

It also has 50+ wax capacitors and an incomprehensible number of coils/chokes!
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Old 5th Jul 2022, 8:55 pm   #2
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Default Re: Dynatron mid 30's 'tuner'

Pictures to show how over designed this really is. The paper dial is a mess and likely to fail apart on any attempt to remove it so I can't make out the ranges. The octal valve socket may not be original or maybe for a connector rather than a valve.

The controls include a 'whistle' filter but would this be from local regenerative receivers or overlapping transmitters? As well as the time it would take to trace the circuit, the cost of the replacement capacitors alone would hurt so it may have to be scrapped.

Does anyone have any info on this or similar Dynatron tuners?
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Old 5th Jul 2022, 11:42 pm   #3
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Default Re: Dynatron mid 30's 'tuner'

Intriguing- must have been a range-topper in its day, surely, and a serious investment for someone at the time. Looks like a pianola-roll sort of set up for the tuning scales, plus ceramic band-change wafers and one ceramic socket for a front-end valve- some sets of the time endeavoured to reach to 41.5MHz TV sound and even beyond, maybe this is one of those. Plenty of IFTs (?) as well as 6 front-end cans and possibly a selectivity switch under some of the IFTs. Wow, pretty much comms receiver sophistication and build quality.
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Old 6th Jul 2022, 12:59 am   #4
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Default Re: Dynatron mid 30's 'tuner'

What a beauty - if reviving it isn't a practical proposition I'd have thought it deserves a place in a museum, possibly the Maidenhead Heritage Centre would be interested? It's from perhaps the most remarkable phase of the Hacker brothers' remarkable career, when as a still tiny operation they went head to head with the might of EMI and the relative might of RGD in creating the most exceptional radio gear, and there's not much actual equipment left to testify to their ambition and achievement.

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Old 6th Jul 2022, 1:26 am   #5
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Default Re: Dynatron mid 30's 'tuner'

You never see any Dynatron grams from that era of just before the war.

On the Dynatron museum site it looks like the Ether Prince of 1939 also uses that tuner. What's of particular interest to me is that when I was a child, I remember going to an uncle's house where I remember a large radiogram in the corner of the room and it had an autochanger with a 'gantry' across the top of the deck, like in that Ether Prince. I've never been able to identify what model that deck was, or even if the radiogram was a Dynatron. One memorable thing was that the tone arm was broken and the story was that there had been a house party and some drunken revellers fell on it, breaking the tone arm.
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Old 6th Jul 2022, 8:33 am   #6
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Default Re: Dynatron mid 30's 'tuner'

The label suggests pre-1936 as they are trading under H Hacker & Sons. I have emailed the Dynatron museum to ask if they have any info on it.
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Old 6th Jul 2022, 8:39 am   #7
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Default Re: Dynatron mid 30's 'tuner'

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Originally Posted by Techman View Post
...it had an autochanger with a 'gantry' across the top of the deck, like in that Ether Prince. I've never been able to identify what model that deck was...
I remember reading that some Dynatron models used a Capehart autochanger, imported from the USA: would it have been one of those?

http://mulhollandpress.com/styled-5/...-18/index.html

https://www.youtube.com/watch?v=nBQWZ4IwaKk
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Old 6th Jul 2022, 10:24 am   #8
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Default Re: Dynatron mid 30's 'tuner'

Lots of Hacker/Dynatron info here: https://www.vintage-radio.info/download.php?id=354

There's a list of known models pp.23-26.

Possibly Keates-Hacker related (p.11).

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Old 8th Jul 2022, 1:06 pm   #9
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Default Re: Dynatron mid 30's 'tuner'

Those Capehart autochangers are an amazing piece of engineering and I've seen video footage of them working before, probably also the one linked to, but it's definitely not one of those that was in that radiogram. I would have thought that it would have been a Garrard model, but I've never been able to identify it as such.

It's very noticeable that pre-war Dynatron products of both table radios as well as large radiograms seem to virtually never come up anywhere, but just post-war models like the one that I've got seem to appear relatively regularly - perhaps very few were sold back then compared to after the war.

I don't really know what to say about that radio tuner chassis shown in the first post. It really needs to be in the radiogram that it was originally fitted to, but of course that's impossible. It's an interesting and rare item, but what can you realistically do with it? I wonder what went into that empty socket, probably a valve rather than a flying lead plug for something else. I wonder if it was the final amplifying stage for the tuner or a detector and AGC diode, or both, perhaps a DD41 or HL41 or maybe an HL41DD?
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Old 8th Jul 2022, 3:13 pm   #10
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Default Re: Dynatron mid 30's 'tuner'

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It really needs to be in the radiogram that it was originally fitted to, but of course that's impossible. It's an interesting and rare item, but what can you realistically do with it?
For sure, the radiogram would be a delight to possess and, if restored, to use: if such an item were ever to come into my possession nothing short of hunger would persuade me to part with it without absolute assurances that the next owner would do their utmost to preserve the thing intact. But, if any sort of society exists in 25, 50, 100, 500 years from now with leisure and civilisation enough to be interested in the technical and social history of electronic design and manufacture, my guess is that even this poor removed artefact will be seen as of considerable cultural value. If it's still around nobody will care whether anyone found anything to do with it here in the twilight years of broadcasting.

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Old 8th Jul 2022, 3:31 pm   #11
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Default Re: Dynatron mid 30's 'tuner'

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But, if any sort of society exists in 25, 50, 100, 500 years from now with leisure and civilisation enough to be interested in the technical and social history of electronic design and manufacture, my guess is that even this poor removed artefact will be seen as of considerable cultural value. If it's still around nobody will care whether anyone found anything to do with it here in the twilight years of broadcasting.
That's exactly why I'm so much for doing a 'historical' repair and replacing only parts that really need replacing to make an item functional.

That tuner will be historically ruined if all the wax capacitors are replaced, and for future historical interest it will become pointless. However, I can fully understand the OP wanting to replace all those capacitors and make up a power supply and run it into an amplifier to see how well it performs. The truth is that none of those capacitors, other than probably a couple, would need to be replaced in order to get it to function reasonably well - it's ultimately down to whether it's going to be 'modernisation' or 'restoration'...or just leave it as it is and maintain its interest for the future.
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Old 12th Jul 2022, 8:18 pm   #12
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Default Re: Dynatron mid 30's 'tuner'

"Searchlight tuning" sounds like fun but I don't think this one has it and the lack of any information, in particular the purpose of the IO socket, is a concern for getting it up & running.
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Old 12th Jul 2022, 9:18 pm   #13
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Default Re: Dynatron mid 30's 'tuner'

When I opened up a 1942 military receiver I found it to be almost as it left the factory.
I was reluctant to replace any components but I wanted to see if it would work.

The heater circuit was OK and there was no serious leakage on the HT.
I used a 6V gell battery to power the heaters.

I monitored the HT current as I increased the HT voltage using a few PP3 batteries.
My Sennheiser HD420 headphones were a good match for the 600 Ohm output.

At 27V it pulled in a strong station.
At 36V it tuned across the MW band and the sound quality was good.
Since the valves were passing microamps, I figured no harm could be done in the short term.
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Old 12th Jul 2022, 9:31 pm   #14
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Default Re: Dynatron mid 30's 'tuner'

What a fascinating thing!

4-gang tuning capacitor - means either that it has 2 RF stages, or it has a 'low' IF and so needs a tracking image-filter.

The 'whistle filter' will probably be something tuned to around 9KHz and installed in the audio-path to remove beat-notes caused by the carriers of adjacent-channel stations

The 'odd' unused valve-socket - could it be perhaps that this thing was once used in the sort of applications like school or factory-sound systems, and the socket was used to feed a small 'local' audio-stage so the operator could tune it in properly before flicking a switch to route the audio to a public-address 'Tannoy' system?

Personally, I would re-work it using modern, non-leaky/non-drifty components and build it into a steel cabinet in the style of something like a CR100 communications-receiver. It is, after all, something close in design/likely-performance to a pre-WWII shortwave comms-RX.
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Old 12th Jul 2022, 9:53 pm   #15
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Default Re: Dynatron mid 30's 'tuner'

Hi.
I'd definitely try to get it working, an engineering masterpiece in my opinion. As a previous poster rightly points out, feed the heaters first and gradually build up the HT. Feeding a pair of headphones is a good idea or even a powered speaker for initial tests. It may surprise you and burst into life with low HT of 50 odd volts. Working out the connections should be relatively easy.
Good luck with it and I'm sure you'll have some fun too.
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Old 18th Jul 2022, 10:35 pm   #16
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Default Re: Dynatron mid 30's 'tuner'

I ventured out into the shed/sauna and took a look at the IO socket. There is another IO valve Mazda DD?? (faded green print) next to it but hidden in the pictures that shares the heater wiring and this would make it an 11 valve AM tuner. The missing valve has Pin 4 & 7 not used which fits with an HL41.

The sleeving on the wires for these two valves is different from the rest of the tuner so maybe an 'upgrade'.
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Old 19th Jul 2022, 8:48 am   #17
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Default Re: Dynatron mid 30's 'tuner'

But an IO base would not fit a HL41..... unless it's actually a MO instead.
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Old 19th Jul 2022, 10:05 am   #18
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Default Re: Dynatron mid 30's 'tuner'

Quote:
Originally Posted by Paul_RK View Post
Quote:
Originally Posted by Techman View Post
...it had an autochanger with a 'gantry' across the top of the deck, like in that Ether Prince. I've never been able to identify what model that deck was...
I remember reading that some Dynatron models used a Capehart autochanger, imported from the USA: would it have been one of those?
The autochanger with the "gantry" is actually the first Collaro autochanger from the 1930s, I have always referred to it as the "bridge" autochanger, because I don't remember it having a model number on the mechanism.

It was built on a heavy 1/4" steel plate, similar to the Garrard RC1, and even had the same insruction plate like the Garrard RC1 with the "coppered" instruction for use text plate adjacent to the platter. Dynatron used Collaro autochangers before going over to Garrard, I can't remember off-hand which other radiogram manufacturers incorporated them.

I have looked on the internet, and surprisingly I cannot find a picture of one, though there is this on YouTube - (though itself is not a video - just a series of images):
https://www.youtube.com/watch?v=q0qcWgJEwS4

Until last year I had one of these autochangers in working condition, I had retained it for years but have no need of Collaro decks, so I took it along to sell at the NVCF in 2021. I didn't want to take it home again so marked it at £5, reduced to free to anyone who showed an interest. None did. I asked the BVWS if it would be worth placing in the upcoming internet auction with no reserve to give it a chance with a different audience, but was advised it was not worth the trouble. It was scrapped.

John.
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Old 19th Jul 2022, 2:01 pm   #19
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Default Re: Dynatron mid 30's 'tuner'

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The autochanger with the "gantry" is actually the first Collaro autochanger from the 1930s, I have always referred to it as the "bridge" autochanger, because I don't remember it having a model number on the mechanism.

It was scrapped.

John
Many thanks for that information, John, that's exactly the one. It's a shame you scrapped it, but we've all done it/had to do it at some time. I would have loved it if I'd been around to just take it off your hands, but it would have been a cumbersome and expensive beast to post off to anyone, so there was really no other choice. I suspect that the radiogram was a thirties Dynatron, unless RGD ever used that deck.

It's early childhood memories of this radiogram and I remember seeing it on a visit to this relatives house, and I can't even remember who the relative was, other than it was in a small Hertfordshire village at a house that had a long allotment type back garden - well many did back in those days.
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Old 19th Jul 2022, 2:35 pm   #20
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Default Re: Dynatron mid 30's 'tuner'

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The missing valve has Pin 4 & 7 not used which fits with an HL41.
It would be - that's why it's missing, then.

The other two valves can't be DD41s as they look to have B5 bases, so suspect that they're two single diodes of some type.

If the rest of the valves were Mazda octal types then I would have suspected VP41s and a TH41, but it looks as though they're not octal types and I think I can see a seven pin type in there with possibly more B5s, but I can't see properly, so could be wrong. There looks to be an unscreened all glass type at the front end - I wonder what that could be? A complete list of the valves would be interesting - I bet you never got anywhere with the Dynatron museum!

You'll correct me if I'm wrong, but I seem to think that you may already have another gram that you could 'borrow' an HL41 from just to try it out. I wouldn't worry about replacing any capacitors whatsoever at this stage, I'd just fit that valve and give it HT and heaters and so long as those two HT decoupling electrolytics in the tall cans hold up (you'll soon know if they don't), I suspect it'll just work.

If you don't have an HL41 to try, then I'd take a chance on an HL41DD Ebay 99p untested special - these valves were used in radios and early TVs, so are pretty much ten a penny. You can re-jig the base socket and run a temporary screened lead from below the chassis for the top cap grid (I'd forgotten that the HL41DD has the triode grid on the top cap when I mentioned it in my previous post), you could then think about drilling a hole for the grid wire and make it permanent if it worked out ok.

What I might do if it were mine and I couldn't find a spare HL41 would be to cut a piece out of the base of an HL41DD near to pin 5 (I think it's pin 5 - without checking the data) and cut off the diode connection to this pin and then run a grid wire down the outside of the valve from the top cap and solder it onto pin 5 in the base of the valve. You could try removing the whole base of the valve, but I think you might be asking for trouble doing that...one way or another you'll be able to work it out.

The octal base socket does look to be 'off-centre' slightly in your picture, so could be a production modification at the factory - all the later Dynatron tuners had an HL41 as the final amplifier with a DD41 doing the double diode job. They all had 'whistle filters' - sometimes on the tuner chassis and sometimes on the amplifier chassis.

Last edited by Techman; 19th Jul 2022 at 2:42 pm.
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