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Old 7th Nov 2020, 8:21 pm   #21
turretslug
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Default Re: R1155 Modern Power Supply

I'm encouraged by the interest in the DF section too- I gather that it was an innovative and effective design at the time, so it's good to see it appreciated! Shame that magic eyes generally are an endangered species though.
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Old 8th Nov 2020, 8:09 am   #22
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Quote:
Originally Posted by turretslug View Post
I'm encouraged by the interest in the DF section too- I gather that it was an innovative and effective design at the time, so it's good to see it appreciated! Shame that magic eyes generally are an endangered species though.
Its a general observation that amateurs have taken equipment and imposed on it their own set of requirements, with zero interest in the history or original purpose of the equipment. Hence the general ripping out of the DF section - if not all the components - then at least the valves, apparently to save heater and HT current.

A proper appreciation of vintage equipment, in my view, is to first understand why the equipment was designed and produced - and to get a grasp on that original requirement. Then try and return the equipment to as near original as possible, and see how well it fulfilled that requirement.

Given that we are talking about power supplies for the R1155 in this thread, I've always found it remarkable that the original supplies were pretty basic affairs - either hefty rotary converters or huge great mains power supply units, with large metal rectifiers and very heavy multiple choke smoothing.

Interestingly there isn't a stabiliser anywhere in sight. Certainly not in the power units, and not in the set either. So one can get away with a very basic power unit - for modern purposes, a simple transformer, full-wave or bridge rectifier, followed by resistance/capacitance smoothing is good enough for the 210V HT rail. As far as I recall the HT current doesn't vary very much as the R1155 is used, so there won't be large variations in HT voltage. And that in turn will reflect on the local oscillator being "stable enough".

That's further helped by the IF being some 4.5kc/s wide at -6dB points, with no fancy features like a crystal filter to demand a highly stable LO. No idea how good the set was on CW, but the matching transmitter, the T1154, chirps like mad on CW. With a transmitter that bad, why bother stabilising the receiver?!


Richard
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Old 8th Nov 2020, 9:03 am   #23
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Default Re: R1155 Modern Power Supply

We have to remember all history. Who's to say that one bit is more important than any other?

In the fifties, Britain was austere, really austere. In the sixties, disposable income was still very very low compared to what we have today. WWII had taught an awful lot of people about radio stuff, and at the end, dumped them back into civvy street. What did they do? They were used to intense demands and challenging work. Going back to being a milkman or painter and decorator or bank clerk must have seemed an anticlimax. Some went into the new TV trade and recycled their radar knowledge. Plenty didn't. But a lot took up amateur radio. The exam and the morse test were a breeze for those in radio op or signalling posts in the war, or national service for several years afterwards. Numbers of radio amateurs and dhortwave listeners surged, and there was a glorious sunspot cycle to welcome them.

So they needed equipment.

In a war, the losing side throws everything and every one they've got into the last ditch effort. Their factories are flattened and they wind up with little equipment left.

The winning side still has their industrial machine going, lots of work in progress, far more tanks and aircraft than needed in peacetime, and amazing amounts of spares and stock.

So there was a war-surplus bonanza. It provided radios and components through the fifties and well into the sixties.

Transmitters are relatively easy to build. A good receiver is a much more serious undertaking. But there were plenty of receivers... more receivers than transmitters.

THere was a pecking order:
The AR88 and HRO were the top of the hit parade.
CR100 came next
THen for people that couldn't afford those ther were R107, R1155 and 19 sets aplenty. Add in some Canadian 22 sets and there were plenty to go around. Any in poor condition went to be melted down.

19 sets had their 'B set' ripped out, and the DF section of R1155 to make way for built-in power supplies and amplifiers to drive loudspeakers.

Accessories and cables mostly got junked. Nobody needed them enough to pay actual money for them. But many sets got saved even if they suffered modification. What you got depended on what you could afford.

In the mid sixties, on five bob a week pocket money, I saved for all I was worth, did odd jobs and got money for Christmas and birthdays. I bought an AR88. Not everyone could do that, not everyone was so fixated, but it was great. Friends had all sorts of things. R1475s had appeared, the B40 not at that time. THere were legends of something, a Racal RA17 but I'd never heard of anyone who'd even seen one. Legends grow.

So people learned a lot. Stuff got boiled down for parts.

Consequently, nowadays, I don't criticise the people who tore out B sets, DF sections and the like. If those people had not been interested, the government would have had no-one to sell the sets to and they would have been melted down, buried in landfill and chucked down mineshafts (disused, I hope!)

But do not forget the intangibles. A lot of knowledge was learned from people playing about with government surplus radios.

We're all a lot richer nowadays. We don't need to scrape and save to the same extent. If an R1155 isn't stable or selective enough for SSB, then maybe it's not the right set to start out with? Why not find something which is made to do that job?

The wartime sets were right for their era. What the people who modified them in civvy street did was right for their era. A modified set tells you something of WWII and also something og the fifties and sixties. Popular histories and TV documentaries tell you loads about WWII for the forties, all about rock and roll and dress styles for the fifties and swinging pop for the sixties. The modified sets are some of the few things that record an era when people were poorer than now, but also very inventive.

David
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Old 8th Nov 2020, 10:20 am   #24
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Default Re: R1155 Modern Power Supply

All good stuff David, as always. I wouldn't deny for a minute that the history you cite is an important part of the UK's story post war. And indeed many of us actually lived through some of that, and benefited from that war surplus "bonanza" you describe. I myself just caught the tail end of it from 1968 onwards - when shops like GWM Radio in Worthing were still going strong, with giant "Les" sitting rather forbidingly in the corner waiting to pronounce on the price of the latest prized item salvaged from the assorted junk on his shelves. Was it going to be within pocket money limits - or not

However, what I am referring to in my post that you responded to, was the original history of sets like the R1155, which I will still contend is far less well known and less well understood, since most of us didn't fly in RAF planes during WWII, and have never had to DF anything in anger!

And that's for a very well known set like the R1155. It gets far more obscure and murky for things like GEE, GEE-H, H2S and other bits of electronics, that were equally bought up as "electronic junk" post war to be pulled apart for bits. Very little knowledge of those items, their original purpose and the way they worked now survives, even among those potentially capable of understanding it, such as people lurking on this esteemed forum! And many of those represent world beating advances in electronics - while the R1155/T1154 was a very run-of-the-mill, turn it quick device of rather limited technical merit.


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Old 8th Nov 2020, 1:55 pm   #25
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It's an interesting general point. From an architectural perspective, the great interest for me is when a basically good-quality building has been adjusted and altered to fit different generations' needs over many years. The best of our national buildings demonstrate this. The problems happen either when groups like the National Trust get involved, and the buildings become museums, stuck in a particular time and dead as far as architecture's concerned, or they get flattened and replaced with noddy boxes. The latter because of advances in technology means it's far easier for a grim company to demolish rather than sensitively alter.

In radio terms, the former is the restoration to original spec., and the latter is the 'use radio chassis as lamp' crowd. I like something in between, as I'm not a museum, but I approach the projects as I'd approach a building. Keep the good bits and make sure it's useful and joyous for the current generation, without destroying what made it good in the first place.

I have an R1155 that has probably been messed around thoroughly by my grandfather, so I'll have to restore it to a state that's of some use to me now. On the subject of DF stages, is this part of a DF/rangefinding apparatus (attached)? It was with the R1155 in his loft...
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Old 8th Nov 2020, 2:08 pm   #26
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BC-929.....Radar interrogator unit ("Rebecca")

Lawrence.
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Old 8th Nov 2020, 2:21 pm   #27
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Thank you, Lawrence! This forum's far better than a search engine algorithm. So, it appears I would need Eureka signals for it to do anything, as it's not something that can be paired with the R1155.

Apologies for the hijack, dsan224!
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Old 8th Nov 2020, 2:38 pm   #28
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Originally Posted by Uncle Bulgaria View Post
Thank you, Lawrence! This forum's far better than a search engine algorithm. So, it appears I would need Eureka signals for it to do anything, as it's not something that can be paired with the R1155.

Apologies for the hijack, dsan224!
Andy from up North is the man on this stuff he should be able to tell you more about what's what.

Used to buy that sort of stuff to dismantle for bits back in the '60's

Good luck with the R1155, owned some of them in the past, when up to spec they perform very well and the original tuning reduction drive is excellent unless you're wearing welders gloves.....they later updated the drive 'cos the WOP's found tuning difficult when wearing gloves at high altitudes "It's cold up here mother"

The BFO oscillator runs at half the IF, HT supply via the contacts on the supply connector plug because the HT-ve rail is not connected directly to chassis.

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Old 8th Nov 2020, 4:38 pm   #29
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Default Re: R1155 Modern Power Supply

Quote:
Originally Posted by trh01uk View Post
Quote:
Originally Posted by turretslug View Post
I'm encouraged by the interest in the DF section too- I gather that it was an innovative and effective design at the time, so it's good to see it appreciated! Shame that magic eyes generally are an endangered species though.
Its a general observation that amateurs have taken equipment and imposed on it their own set of requirements, with zero interest in the history or original purpose of the equipment. Hence the general ripping out of the DF section - if not all the components - then at least the valves, apparently to save heater and HT current.

A proper appreciation of vintage equipment, in my view, is to first understand why the equipment was designed and produced - and to get a grasp on that original requirement. Then try and return the equipment to as near original as possible, and see how well it fulfilled that requirement.



Given that we are talking about power supplies for the R1155 in this thread, I've always found it remarkable that the original supplies were pretty basic affairs - either hefty rotary converters or huge great mains power supply units, with large metal rectifiers and very heavy multiple choke smoothing.

Interestingly there isn't a stabiliser anywhere in sight. Certainly not in the power units, and not in the set either. So one can get away with a very basic power unit - for modern purposes, a simple transformer, full-wave or bridge rectifier, followed by resistance/capacitance smoothing is good enough for the 210V HT rail. As far as I recall the HT current doesn't vary very much as the R1155 is used, so there won't be large variations in HT voltage. And that in turn will reflect on the local oscillator being "stable enough".

That's further helped by the IF being some 4.5kc/s wide at -6dB points, with no fancy features like a crystal filter to demand a highly stable LO. No idea how good the set was on CW, but the matching transmitter, the T1154, chirps like mad on CW. With a transmitter that bad, why bother stabilising the receiver?!


Richard

The other thing to remember was the expected life of the aircraft crews, why spend a fortune on a Rolls Royce when a mini would survive the few expected trips.
Poignant today of course.
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Old 8th Nov 2020, 5:01 pm   #30
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Quote:
Originally Posted by M0AFJ, Tim View Post


The other thing to remember was the expected life of the aircraft crews, why spend a fortune on a Rolls Royce when a mini would survive the few expected trips.
Poignant today of course.

Tim,

I agree with your point - however that relates specifically to the quality of construction I think, and rather less to the performance.

The original performance had to be "adequate", to paraphrase those famous R-R people. Clearly "adequate" in this case didn't run to stabilised power supplies - and that was probably because the expected radio links, ground in the UK, to planes over Germany, or plane to plane, was extremely non-demanding. Simple line of sight in fact. No need for bouncing anything off the ionosphere.

So the performance could be no better than "so-so", with just ordinary AM bandwidth being OK, even when CW was in use. In the plane, the voltage rails may well have been quite stable once the plane was in the air, obviously with the engines running. As far as I recall the power system had generators charging 24V batteries - producing a roughly 28V rail, which would then power some hefty dynamotors. Those things have quite a lot of inertia and thus their output voltage is pretty stable over a period of seconds, and possibly minutes. So no need to be chasing signals up the band.

And as far as temperature goes.....it was generally agreed that it was blooming freezing in those Lancasters, as someone has already pointed out about the use of gloves......no doubt not just cold, but also cold and stable.


Richard
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Old 8th Nov 2020, 5:43 pm   #31
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While I am all for keeping things as they were intended, we need to remember back then for a start, there was a large surplus of gear and of course pretty cheap.
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Old 8th Nov 2020, 7:32 pm   #32
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Originally Posted by trh01uk View Post
it was blooming freezing in those Lancasters
Richard

Apart from the Wireless Operators position, apparently...
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Old 8th Nov 2020, 7:46 pm   #33
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Presumably being broiled by a glycol heat exchanger in his place near the wing root?
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Old 8th Nov 2020, 7:54 pm   #34
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Back on Topic Please

Cheers

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Old 8th Nov 2020, 8:56 pm   #35
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Originally Posted by Uncle Bulgaria View Post
It's an interesting general point.

In radio terms, the former is the restoration to original spec., and the latter is the 'use radio chassis as lamp' crowd. I like something in between, as I'm not a museum, but I approach the projects as I'd approach a building. Keep the good bits and make sure it's useful and joyous for the current generation, without destroying what made it good in the first place.
I like to aim somewhere in between, too- I think it's fair enough to say that with something like an R1155, there'll be a good number of original (or near original) condition examples in museums and with privare collectors that no historical crime is being committed by the careful and sympathetic replacement of degraded passive components and acquisition of missing/previously stripped sub-assemblies in order to end up with a properly working example. It can actually be quite satisfying to find out just hiow well vintage gear can work once the good bits- i.e. valves, wound components etc.- are allowed to give of their best with passives that are somewhat better than they were in the day. What I specifically avoid is the drilling/cutting/scarring of original metalwork- indeed, one of the more satisfying and time-consuming parts of an overhaul can be the fabrication of adapter plates so that substitute power connectors, low-impedance output transformers and so on can be added to veteran specialist (aviation-orientated etc.) apparatus in order to make a more demonstrably day-to-day useful and interesting device without making it impossible to restore it to genuine as-was status.
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Old 8th Nov 2020, 8:58 pm   #36
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I'll try and get a photo out re the [probably 1950's] PSU] that came with my 1155 [post 20*]. Excellent overview David but I can't see there's is any criticism of sets being stripped out it was just the way it was then as you so clearly explained and I [for example] was simply reporting what usually happened. Who can claim it was a bad idea in the post war years? I'm not sure that a lot of owners [as you say it was a rare achievement to get one at all] would have thought it even possible possible to restore the DF section back then It was years before I saw an aerial unit for example! When dsan sorts his PSU it will be great to see a high quality restoration of the whole system. I think you're pecking order re sets is probably accurate but from my [teenage] point of view I always thought of a set with a "proper" half moon dial was very desirable but never got one. The R107 "moonie" was a bit clunky but the R1155 seemed the business although I never got hold of either Receivers like the 19 Set [unaccountably in demand still with all the accessories] and especially the Canadian 52 Set had very crude dials in my view [I had both of these ] but they were always be at "beggars can't be choosers" end of the list for me

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Old 9th Nov 2020, 3:08 pm   #37
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Hopefully this post will be strictly “on topic”!

I will outline a project I undertook a few years ago to build a modern power supply for an R1155 receiver. Strictly the project was for a complete T1154/R1155 system, but I will describe just the receiver part of this. The psu was built – but I no longer have it, as it was done for a client and delivered. I may have the odd photo which I can share.

I started by establishing the requirement. Sure we have a rough idea of the basic volts and amps required – but I refer to more subtle things like:

  • How much ripple is allowed on the HT rail?
  • How stable should I make the HT voltage?
  • Should the LT be DC or AC?

And I was aware that the original mains PSUs for T1154/R1155 were enormous brutes, with multiple chokes, etc. It seemed back in 1940 that the “requirement” wasn’t straightforward. And incidentally, I didn’t just want to get a R1155 “making a bit of noise” – I wanted it to work to the original spec. Trouble is that while the government would have definitely delivered a clear requirement spec to the original designers (Marconi?) that document is most likely gone for ever. I've never seen anything – though I suppose a search through the records at Kew might turn up something.

So I decided to reverse engineer the requirement…..by looking at what the original designers produced, and asking “How did that perform?” I didn’t have a working original T1154/R1155 mains psu (actually the pair) to hand, so I turned to the technical description of them – document enclosed (AP1186E Vol.I, Sec.6, Ch.4).

The basic amps and volts requirement is given as:
  • HT: 210V DC at 110mA max (that's all for the R1155)
  • LT: 7V DC at 13A max

The LT is misleading because most of that 13A is actually going to the T1154. The keying relay alone takes some 4A! The actual LT requirement for the R1155 has to be established separately by considering the valve heater current demands, and when that is done by recourse to AP2548A, it tots up to 4.67A with all the valves present. So a nominal 5 amp requirement.

What about the 7V DC bit? Well the 7V is to allow for voltage drop in potentially long cables and various connectors, so that the valves actually get their nominal 6.3V, when the whole system is taking upwards of 10 amps or more. We can relax the 7V to 6.3V provided the cabling is short - i.e. a couple of feet or so of standard cabling. There is no actual need for DC LT in the R1155 alone. The DC requirement comes from the T1154’s keying relay.

So with the LT established as around 6.3V AC at 5A, lets turn to the HT. The original circuits are shown in the extract in my simulation results document, with values taken from the text of AP1186E. I then supplemented that info with some measurements on an actual original PSU, which was not working due to having duff metal rectifiers.
  • Transformer gives 270V rms off load, with very roughly 50 ohm source resistance
  • Chokes measure 11H (zero current) with series resistance of 105 Ω
  • Other components near to nominal values. I had to guesstimate the capacitors’ ESR at 0.5 Ω

The point of all this detail is that the next step is to simulate the original power unit to see how the original design performs for stability and ripple.

Rather than trying to grapple with a full simulator (like pSpice) I use a dedicated psu simulator, from “Duncan’s amp pages” – which is available for free download.

As it turned out, this simulator is severely taxed by aspects of this ancient psu – notably the metal rectifier. This may well be an instance where resorting to algebra and spreadsheets would give a better result – but I didn’t bother this time, mainly because I had no definite data on the metal rectifier anyway.

I have attached the original simulation schematics and results I recorded when doing the design work some five years ago. I’m aware that the simulation is a compromise – mainly due to the original metal rectifier, for which there is nothing in the simulator library and there is no data available that I know of. So I used a 4 x 1N4007 bridge then tried to simulate the increased series resistance of a metal rectifier by putting a series 100 ohm resistor before the filter stages. That value of 100 ohms was derived from reading early texts on metal rectifiers and their performance (Bell System Journal for 1953, “Selenium Rectifiers – Factors in their Application”, Gramels). Better ideas welcome!

The simulations used a number of conditions:
  1. 1. With a 8.8k load. This is the supply at startup, with the R1155 connected but the valve heaters cold. 8.8k represents the 50k resistor in the psu in parallel with the fixed resistive loads in the R1155 which are permanently in-circuit regardless of mode.
  2. 2. With a load of 2.8k giving an output current of about 75mA. This represents the receiver running in normal receive mode without any DF systems being used.
  3. 3. With a load of 1.9k giving an output current of about 110mA (design spec).

Results - Condition 1:
Load value = 8.8kΩ
Load current = 26mA
HT voltage = 232V
Ripple (Vp-p) =1.6


Results - Condition 2:
Load value = 2.8kΩ
Load current = 77mA
HT voltage = 214V
Ripple (Vp-p) =1.6

Results - Condition 3:
Load value = 1.85kΩ
Load current = 110mA
HT voltage = 203V
Ripple (Vp-p) =1.6


So the conclusion of all that is that HT rail is 208V ± 5V, and the ripple is pretty steady at 1.6V p-p. That remarkably stable HT rail is mainly due to the use of a L-C filter, with the addition of a background load (condition 1).

In my next post I will describe the modern version of this original circuit, and how well it performed compared to the original.

Richard
Attached Files
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File Type: pdf Simulation of Type 114 power supply - HT1.pdf (1.47 MB, 18 views)
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Old 9th Nov 2020, 9:17 pm   #38
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Following on from post #37, where I attempted to get close to the original design specs, I will now describe what we actually produced.

Quite a bit of time was spent playing with high voltage solid-state regulators, and discrete regulators, because I was determined to try and produce a supply that performed as well as the original, but was a good bit lighter - and smaller! A few of the semiconductor regulator solutions were knocked up and tested on the bench. The trouble with them is that they produced a very stable voltage (tick!) with very low ripple (tick!) - BUT they were extremely easy to destroy, sometimes with utters stupidity, like shorting the HT line to ground, and sometimes it just died without any apparent help.

Given that the supply was being made for a radio user, not necessarily very technical, I decided in the end that semiconductor cleverness was probably a bad idea. So I returned to the ultra-simple solution of a bridge rectifier, followed by a single L-C filter. Same principle as the original, but with high value C available these days (they weren't in 1940), and also the ability of a colleague to wind any size choke I wanted, it sounded promising.

After a few simulations with PSUD2, I came up with this schematic:

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Simulation results as follows. First up, the start-up voltage with the 8.8k load:

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Then the same, steady state after a couple of seconds:

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Then with a load of around 75mA, 8.8k ohms, representing the R1155 on normal reception mode with no DF use:

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Then finally at maximum (spec'd) current of 110mA:

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A summary of the results under these three conditions are:

Results - Condition 1:
Load value = 8.8kΩ
Load current = 25mA
HT voltage = 220V
Ripple (Vp-p) =0.35


Results - Condition 2:

Load value = 2.8kΩ
Load current = 76mA
HT voltage = 212V
Ripple (Vp-p) =0.35

Results - Condition 3:
Load value = 1.85kΩ
Load current = 112mA
HT voltage = 207V
Ripple (Vp-p) =0.35

So the ripple is now a lot lower than the original psu managed. The voltage stability is also better dropping only 5V (compared to 11V) with the load ranging over 75 to 110mA.

And the actual circuit is about as simple as its possible to make a linear psu. The only drawback is the cost of the choke - I decided the increased weight compared to a SS regulator was not that important, given it was "lost" when put in with the T1154 transformer etc.

Chokes are available - often in junk boxes, sometimes at rallies, and of course you can do what we did - wind a new one from scratch - or get the helpful people on this forum to make one for you.


Richard

P.S. I forgot to add that the simulations showed the 1N4007 PIV rating of 1000V being exceeded in the first 0.5 seconds after switch on. That doesn't matter for a simulation - but it's not a good idea to go with that in real life! I think we actually used some 1500V diodes in the end - BY228s as I recall.
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Old 10th Nov 2020, 2:03 pm   #39
Ed_Dinning
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Default Re: R1155 Modern Power Supply

Hi Richard, thanks for all the work on the PSU and the details from the AP's.

The DC heaters are a must, I'm told, when using the transmitter to reduce the 50Hz mod.

I've used a FET for the 1155 filter and made it adjustable as it is easily done. This is more of an active filter for hum reduction than a true compensated regulator. I'm told the limited range adjustment (200 to 240V) makes it easier to find a low drift point for the 1155 oscillator.

The EHT supply seems to benefit from an LCL filter where the first choke is a swinging type. It is also possible with some of the transformers available to have hi/lo EHT switching

There is a significant noise reduction if the HT and EHT negative rails are bypassed to ground with a 0.1uF paralleled with a 1Meg.

Ed
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Old 10th Nov 2020, 3:01 pm   #40
trh01uk
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Default Re: R1155 Modern Power Supply

Quote:
Originally Posted by Ed_Dinning View Post
Hi Richard, thanks for all the work on the PSU and the details from the AP's.

The DC heaters are a must, I'm told, when using the transmitter to reduce the 50Kz mod.

I've used a FET for the 1155 filter and made it adjustable as it is easily done. This is more of an active filter for hum reduction than a true compensated regulator. I'm told the limited range adjustment (200 to 240V) makes it easier to find a low drift point for the 1155 oscillator.

The EHT supply seems to benefit from an LCL filter where the first choke is a swinging type. It is also possible with some of the transformers available to have hi/lo EHT switching

There is a significant noise reduction if the HT an EHT negative rails are bypassed to ground with a 0.1uF paralleled with a 1Meg.

Ed
Ed,

I would agree with you on the need for DC when the T1154 is being powered. The keying relay alone dictates it - unless you are going to make internal mods to the Tx - and that's regardless of any problems with the direct heaters of the PA valves (PT15s). I've not heard of a problem with feeding the R1155 heaters with AC though - and as far as I recall when I had the bits in my hands it all worked fine.

Of course, its possible to make semiconductor regulators using BJTs, MOSFETS etc. I had a rather negative experience of them as I described - too easily destroyed - and we happened to have the inductor winding facility that made the production of a choke very easy. Of course not true for all!

With reference to the 1200V EHT supply - which is strictly speaking outside the scope of this thread - I did in fact stick to the original recipe in AP1186E - except that I adopted the same strategy of a single L-C stage filter. I used the same amount of L, and loads more C as I recall. Simulating it gave similar results as the original achieves. its important to use a filter that gives a stable output voltage, because of course the load current varies from 0 to 100mA (or so) rather rapidly in CW mode - and the T1154 really doesn't need any encouragement to makes its chirp any worse!!

I am not familiar with an L-C-L filter, which will be essentially the same as I had but with an extra choke, and as you say, the first choke swinging. What benefit does that offer? It would appear to have the obvious drawback of even more lumps of iron - more weight, and more money!


Richard
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