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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 10th Nov 2020, 6:40 pm   #41
Radio Wrangler
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Default Re: R1155 Modern Power Supply

Shunt C - Series L - Shunt C filters are common in filter design books. The thing to note is that they go low-Z out of band.

Series L - Shunt C -Series L filters according to the books can give the same response. BUT the stopband achieves rejection by going high-Z

So suggesting they are equivalent is rather misleading as it often relies on ideal conditions of matched source and load impedances applied to the filter across not only the passband but also the stop band. Life isn't usually so kind.

David
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Old 10th Nov 2020, 9:04 pm   #42
Ed_Dinning
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Default Re: R1155 Modern Power Supply

Hi Richard, yes an 1155 on its own does not need DC heaters.

The swinging choke technique is described in the various amateur radio hand book as helping to stabilise the EHT rail. I would be interested if you could run a simulation on it .
Typical choke is 5 to 20H at 20 to 200mA

Ed
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Old 10th Nov 2020, 9:39 pm   #43
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Default Re: R1155 Modern Power Supply

Quote:
Originally Posted by Ed_Dinning View Post
Hi Richard, yes an 1155 on its own does not need DC heaters.

The swinging choke technique is described in the various amateur radio hand book as helping to stabilise the EHT rail. I would be interested if you could run a simulation on it .
Typical choke is 5 to 20H at 20 to 200mA

Ed
Ed,

well I will certainly give it a go. I will firstly look at some of my old amateur radio handbooks and see if I can see this technique described. I've not seen it in any equipment as far as I can recall.

Just to check your swinging choke spec......its 20H at 20mA, and 5H at 200mA?

Richard

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Old 10th Nov 2020, 10:29 pm   #44
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Default Re: R1155 Modern Power Supply

Hi Richard, yes that is approx what it is, other values may be used in the books.
Simply put, an air-gapped choke with a tapering or stepped air gap.

Ed
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Old 10th Nov 2020, 11:11 pm   #45
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Default Re: R1155 Modern Power Supply

G'day everyone.
Probably not of much value to this thread but I have a "Type X" power supply here.
Made by Airzone in Melbourne for the war effort.
It was used to power the R1155 / T1154 setup from 240V mains.
It is very heavy and definitely a 4 man lift.
Picture here. http://www.tuberadio.com/robinson/Au...dios/TYPEX.jpg
Copper oxide or selenium rectifier for the low voltage supply and a pair of 866A mercury vapour rectifiers for the HT.
I have it here but it is not easy to get to as it is toward the rear of my shed and I have not really looked at it for over 15 years.
I am having major abdominal surgery in under 2 weeks time and will be out of action for about 8 weeks so my surgeon tells me so I can't help in the short time. Much as I would love to dig it out and be an active part of this thread.
Sadly I do not have any details other than Ray's pictures.
I intend to keep it intact and use it to power an ART-13 TX.

Cheers.
Robert. VK2ZWZ.
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Old 11th Nov 2020, 9:15 am   #46
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Default Re: R1155 Modern Power Supply

Quote:
Originally Posted by Ed_Dinning View Post
Hi Richard, yes an 1155 on its own does not need DC heaters.

The swinging choke technique is described in the various amateur radio hand book as helping to stabilise the EHT rail. I would be interested if you could run a simulation on it .
Typical choke is 5 to 20H at 20 to 200mA

Ed
Ed,

given that this question is really outside the scope of a strictly "R1155 only" power supply, I will start a new thread for that one once I have a few results. Probably in the "Components and Circuits "section with a cross-reference to this thread.


Richard
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Old 11th Nov 2020, 9:28 am   #47
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Default Re: R1155 Modern Power Supply

One further comment I would make on a R1155 power supply is that I am aware that most of the designs put forward in the past have not bothered at all with voltage stability. The standard C-L-C filter - or more often C-R-C filter - has been used as entirely adequate for the job. So why go to the bother of the L-C-L-C design in the original, or the simpler L-C design I used?

The answer can only be that voltage stability is actually rather important. So then, why do R1155 users not report problems with voltage stability - or in fact the secondary effect of it - namely chronic receiver drift, due to the HT voltage on the local oscillator varying?

I think the answer to that is that virtually all users (since the end of WWII!) have not used the R1155 as originally intended - that is with the DF circuits in and out of use. Its been used in a very simple way - just as a communications tool (I'm not knocking that of course!) And in that mode, the current drawn from the supply is pretty stable around the 70 - 75mA mark.

Its only when other modes are selected, that other valves come into play and of course, the HT current will change - notably upwards - nearer to that 110mA limit. And of course, the last thing you need when changing mode - is the receiver drifting off the signal being monitored!

Horses for courses come to mind.....


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Old 11th Nov 2020, 8:26 pm   #48
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Default Re: R1155 Modern Power Supply

Hi Richard, back on the 1155 PSU, I have seen an AM unit that used the LcL configuration and I'm sure the first choke was a swinging type.

Some earlier users of 1155's reported that it was useful to be able to vary the HT voltage over a small range as an aid to reducing frequency drift, I've never tried to verify this

Ed
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Old 13th Nov 2020, 9:13 am   #49
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Default Re: R1155 Modern Power Supply

Returning to the question of how to make a new power supply for a R1155 (or indeed any similar valve receiver) I have already given my own solution to the problem - but I had the luxury of newly made iron-cored wound components (transformer and choke) to any spec that I wanted. What do we do if that is not available - and we don't want to pay the going rate for newly wound parts?

One approach is to scour the rallies (when there are any!), ask people to turn out their junk boxes and possibly scavenge the parts from some junk valve radio. Many domestic sets from the 30s, 40s and 50s will have a mains transformer designed to produce a HT rail of around 200 - 250V. That is likely to be fine for a current demand of 75mA or so. Of course, this takes a fair amount of technical expertise in assessing "one-off finds" as to whether they are suitable or not. Many people don't have the confidence to do that.

That approach is likely to be less good for the heater voltage requirement, which is 6.3V AC at about 4 amps - if you leave the DF valves out. As far as I know, that's a bit high for your average scavenged domestic radio mains transformer. One alternative is to buy a separate heater transformer. A typical offering would be the first offering on this supplier's page, which is a 230V mains tranformer with 2 x 6V secondaries, with a total power of 50VA. Cost is 16.66 plus postage.

I would run the two secondaries in parallel to give a total current capability of 8A or so. With 240V going into a 230V primary, and the transformer lightly loaded, the actual voltage is likely to be close to the required 6.3V. I would still use chunky wire to minimise voltage drops between the PSU and set though, along with the original Jones plugs, which should keep losses as low as possible.

When it comes to buying a brand new transformer for the HT rail, it seems to be near impossible to find anything like a 250V secondary. The highest secondary voltage RS offers in chassis mounted transformers is 50V. That could be voltage quadrupled up to 200V. They offer a toroidal transformer at 115V output, but that costs over 50. I see Cricklewood Electronics offer this toroidal transformer which will do 70V AC, but that still costs near 30, probably because its total overkill for our purpose here at 160VA rating (we only need about 20VA!). And it will still need a voltage tripler to get our 210V rail.

Conclusion: its technically possible to design a brand new psu using off-the-shelf readily available parts, but it won't be cheap. Somewhere between 50 and 100 in parts alone, most of which will be the transformers.

Now we know why simple PSUs suitable for this purpose offered on Ebay are snapped up like hot cakes, and fetch "silly" prices!


Richard
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Old 13th Nov 2020, 11:29 am   #50
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Default Re: R1155 Modern Power Supply

Some of these old comms receivers aren't that fussy for HT stability, I tried dropping the HT on a HRO I used to have by a considerable amount, the tuning drifted less than 3kHz.

Lawrence.
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Old 13th Nov 2020, 1:05 pm   #51
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Default Re: R1155 Modern Power Supply

Capacitor-input rectifier-filters do peak rectification to a first approximation all the time.

Choke-input rectifier-filters give a DC output equal to the mean of the rectified AC... appreciably less than the peak rectified voltage of the capacitor input job. BUT if the current demand goes low, the voltage rises to the peak rectifier value. So to make a choke input job give a reasonably stable output voltage, there is a minimum current which must be taken. It has to be enough that the rectifier never drops out of conduction over its full half-cycle. This forces you often into larger choke inductances and larger cores than you'd like. Otherwise the choke input job is kinder on rectifiers passing smoother less concentrated current waveforms through them.

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Old 14th Nov 2020, 7:35 pm   #52
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Default Re: R1155 Modern Power Supply

Quote:
Originally Posted by Ed_Dinning View Post
Hi Richard, back on the 1155 PSU, I have seen an AM unit that used the LcL configuration and I'm sure the first choke was a swinging type.

Some earlier users of 1155's reported that it was useful to be able to vary the HT voltage over a small range as an aid to reducing frequency drift, I've never tried to verify this

Ed
Ed,

the only AM (=Air Ministry I presume) power units for the 1155 I am aware of are those monsters described in AP1186E, which I posted further up this thread. The chokes in there are fixed values - no swinging chokes there - see the note about L3 and L4 in paragraph 11, where the values are given as 10 to 12H at 110mA.

There may of course be some other AM psu designed solely to run a R1155. Can't comment about that - except to say I have never heard of one.

I should also say that I will have to back out of offering to simulate the swinging choke version of any psu. I've actually done a bunch of such simulations, but I then spoke to the designer of the PSUD2 simulation software, and he pointed out that simulating a swinging choke is actually vastly more complex than his simple software package will allow for.

The ripple current through the choke can easily vary from 0 to 200mA over one cycle - and of course the inductance will vary too through the cycle. Add in magnetic hysteresis and you have a very complex situation here.

One last thought on swinging chokes.......and that is that they were apparently only used as a cost saving measure. To some extent they can reduce the amount of copper and iron required, since the inductance at the high current load is allowed to fall to some quite low value. That's a bit academic these days - and I rather doubt any seller of old chokes is going to give a discount because its a swinging one! Probably double the price because its a "rare item".

I can't comment on your point that there some "sweet spot" for HT+ voltage for the R1155. I am surprised anyone has done the measurements and analysis to find out such obscure information. Sounds like a whole other topic for another thread to me...!


Richard
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Old 14th Nov 2020, 7:48 pm   #53
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Default Re: R1155 Modern Power Supply

Most of the 'classic' 1940s/1950s designs for such PSUs will assume you'll be working with a valve-rectifier and old-style low-value [less-than-50uF] electrolytic capacitors, both of which also suggest involving a choke.

While that was the path-to-success in the 1950s, these days we have silicon diodes and high-voltage-high-capacitance electrolytic-capacitors are everywhere.

For the HT I'd suggest looking at something like what's called a "1:1 panel transformer" - used in loads of industrial applications, so are cheap. Then bridge-rectify the secondary using modern [UF4007] silicon diodes and smooth with 1000uF or so of cheap 450V-rated electrolytics. This will provide a 'low-source-impedance' DC supply that won't wander up or down too much as your radio's consumption varies.
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Old 14th Nov 2020, 9:10 pm   #54
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Default Re: R1155 Modern Power Supply

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Originally Posted by G6Tanuki View Post
This will provide a 'low-source-impedance' DC supply that won't wander up or down too much as your radio's consumption varies.
I'll say! I'd want to include a lamp limiter - a 100W bulb would be about right
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Old 14th Nov 2020, 10:01 pm   #55
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Default Re: R1155 Modern Power Supply

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Quote:
Originally Posted by G6Tanuki View Post
This will provide a 'low-source-impedance' DC supply that won't wander up or down too much as your radio's consumption varies.
I'll say! I'd want to include a lamp limiter - a 100W bulb would be about right
That's presumably a reference to the very poor state of the average R1155, and the fact that many new owners will just want to connect up a power supply - just "to see what happens"!

That could easily result in the demise of various bits inside the R1155 - or the power supply. Which is the main reason I refused to go with any semiconductor regulator when I was designing a power supply for this job. Far too easy to blow up the supply - particularly with inexpert users.

Richard
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Old 14th Nov 2020, 11:54 pm   #56
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Default Re: R1155 Modern Power Supply

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Originally Posted by trh01uk View Post


I should also say that I will have to back out of offering to simulate the swinging choke version of any psu. I've actually done a bunch of such simulations, but I then spoke to the designer of the PSUD2 simulation software, and he pointed out that simulating a swinging choke is actually vastly more complex than his simple software package will allow for.


Richard

It does sound like a challenging problem to come up with a suitable model for a swinging choke to plug into a simulator.


In practical terms you can simulate a psu at min output current to determine what inductance is required to keep the rectifier current continuous then go again at the max output current to see how low it can drop before rectifier current again becomes discontinuous. It's then a problem for the choke designer to come up with the cheapest way of meeting or exceeding these limits!


Historically, someone somewhere will have published useful tables for just this either derived analytically or empirically but if you weren't in the business back then and know where to look for the information simulation can be your get out of jail free card
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Old 15th Nov 2020, 12:07 am   #57
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Default Re: R1155 Modern Power Supply

4 AMPS for heaters, post 49*, seems a lot by later standards but as I understand it, that was common with side contact valves etc, pre-war, so maybe it wasn't so unusual when R1155's were being built. That was a very detailed PSU analysis you carried out there Richard [miles above my comprehension] but unless I'm confused [very likely] you went back to basics in the end. There was a bit of a "Holy Grail" aura around the PSU and the floating negative bias circuitry, at one time but others just seemed to turn up and sort it [and the set] without a second thought. I wonder how the OP is getting on?

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Old 15th Nov 2020, 10:07 am   #58
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4 AMPS for heaters, post 49*, seems a lot by later standards.........

Dave W
Dave,

for clarity I will list the actual heater currents for the valves the R1155 contains. If 4 amps "sounds a lot" - its a good bit less than the 4.7A that is the "official total" when all the valves are fitted. Here's how that breaks down:

Receiver section:

V3 RF amplifier VR100 Ih=0.3A
V4 Mixer/Local oscillator VR99 Ih=0.3A
V5 1st IF amplifier VR100 Ih=0.3A
V6 2nd IF amplifier VR100 Ih=0.3A
V7 Detector/AGC/audio VR101 Ih=0.65A
V8 Audio output VR101 Ih=0.65A
V10 Tuning indicator VI103 Ih=0.3A

Total heater current receiver: 2.8A

DF section:

V1 DF Switching VR99A Ih=0.3A
V2 DF Switching VR99A Ih=0.3A
V9 Visual meter switch VR102 Ih=1.3A

Total heater current DF: 1.9A

So.....the "4A heater current" is in fact incorrect - its 2.8A if the DF valves are removed, and 4.7A if they are fitted. Someone wanting to just use it in comms mode, could get away perfectly well with a 3A LT power source.

The valve compliment in the receive section is about average for a WWII receiver. The DF section is unusual and adds nearly another 2A- which is probably why most users of the set have routinely discarded those valves. Its only with the push for authenticity in recent decades that people have started to grapple with the full system.


Richard
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Old 16th Nov 2020, 1:54 am   #59
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Default Re: R1155 Modern Power Supply

Thanks for that explanation Richard. I see what you mean! It's accumulative in fact although, as they say [in Lancashire at least] "It all mounts up!". I think I've gained my impression of this from reading about Radio or Tv set restorations, where the person trying to revive things often talks about a generic problem with certain valves needing a four amp supply and has to cobble something together [separately] to make up the difference

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