R1155 - guide to restoration

[XTC]

I built a solid-state HT regulated PSU which is a modified version of this design http://www.duncanamps.com/technical/mosfet.html

modified so that rather than produce 250V @ 25mA it delivers 200V to 230V (set with a preset) @ 100mA or more (it has heatsinking to match). It has no detectable ripple. It was built on plain matrix board.

I can produce pictures and a cct diagram if anyone is interested.

The correct HT voltage for 1155s was stated as 200V in the early literature and 220V in the later literature, and especially, if you are not going to replace caps you don't want to, I think you're best to stick to that. Some of the older PSU designs for the 1155 produce much more than 200V. If you use solid state rather than valve rectifiers these PSUs will deliver about 1.4 times the transformer RMS voltage on switch on, which gives a fair chance of damaging something.

The HT for the 1155 is floating, that is neither side is connected to earth. The set acts as a potential divider for HT with the valves one side of earth and resistors on the other to give the -ve bias. The 6.3V supply is earthed on one side as it's chassis return.

Using the solid-state regulator makes for a much easier choice of mains transformer. I use a 300V-0-300V transformer which came out of a radiogram.

The HT demand for the PSU needs thinking about. It will be lightest if the DF valves are missing and there is no internal or external audio O/P valve powered from the same transformer. In that case you may get away with a transformer from a tabletop domestic radio, but watch the heater current demand.

I'm sure the heater current is about 3A total. You can work it out for the set in question by adding up the heater current for valves from a databook. 3A is quite a lot and the Maplins valve mains transformer doesn't deliver anything like that, as I recall. You're stuck with finding a transformer which can deliver that heater current.

Some people argue that the heater current should be DC because that's what it would have been in the aircraft, and there might be problems with hum. I use AC as did the published amateur PSU designs and the one used by the forces for ground based operation. I notice no problems with hum at all. Producing 6.3V DC @ 3A seems like an unnecessary complication without any advantage to me.

An external audio O/P stage could be valve based, but what's the point? It just gives more HT current to find. It's easy to build an external amplifier using an LM386 or similar, or adapting a computer speaker with internal amplifier.

The step-by-step guide is a worthy project, but I'm doubtful about it. 1155s are mostly codged to a state where it isn't possible to restore them to original, and if they are original, they are still 65 years old with deteriorating components and especially wiring, if you are unlucky. They present you with a series of decisions to make and be happy with, to a much greater extent than any other set I can think of. For these reasons, rather than complexity, I'd say they are not a good starting set.

A document of any sort has to be written with the intended audience in mind. The broader the audience, and the more complex the message, the harder it is to do well, because you can assume less. What level of experience is being assumed by this guide?

Pete.

[MichaelR]

Originally Posted by XTC

The step-by-step guide is a worthy project, but I'm doubtful about it. 1155s are mostly codged to a state where it isn't possible to restore them to original, and if they are original, they are still 65 years old with deteriorating components and especially wiring, if you are unlucky. They present you with a series of decisions to make and be happy with, to a much greater extent than any other set I can think of. For these reasons, rather than complexity, I'd say they are not a good starting set.

A document of any sort has to be written with the intended audience in mind. The broader the audience, and the more complex the message, the harder it is to do well, because you can assume less. What level of experience is being assumed by this guide?

Pete inmay ways I think you have answered in a way that David is trying to encourage.

a... you have come up with a worthy suggestion that has been explained technically very well for the first part of getting one of these receivers working.

b... You can never really gauge the comprehension of a wide diverse audience. For example you state that the R1155 chassis is floating, I do not believe it is because it is meant to be connected to earth however its supply requirenment is for a 200 v supply with respect to earth and a
-30V supply wrt earth.It is only by discussion that understanding and knowledge can be developed.

c... Most people will not want overhaul an R1115 but that does not mean that they cannot learn from the thought and design process of the project to apply that inspiration to something else.We have at least 2 people who want to go through with the project and I for one am very grateful for your comments as it now makes me think again about the external PSU and Amp build.

d... As a hobby you take the technical side as far as you want to or are able to go, If somebody does not understand something at least this forum has the reputation of being very helpful to those trying to find answers.

e... It is not a step by step guide that is being proposed to be produced but an example of how you have responded with a quality suggestion to the PSU consideration. Imagine this being replicated all the way through the project , it would produce an excellent collection of thoughts.

I know it is only a mute point but I would like to clarify my understanding of the "floating chassis" idea.

I no doubt David will reply with his thoughts

many Thanks
mike

[XTC]

Originally Posted by MichaelR

Pete inmay ways I think you have answered in a way that David is trying to encourage.

OK. I'm willing to be helpful, but I had the impression that some sort of 'instant expertise' document was proposed.

Originally Posted by MichaelR

b... You can never really gauge the comprehension of a wide diverse audience. For example you state that the R1155 chassis is floating, I do not believe it is because it is meant to be connected to earth however its supply requirement is for a 200 v supply with respect to earth and a
-30V supply wrt earth.It is only by discussion that understanding and knowledge can be developed.
I know it is only a mute point but I would like to clarify my understanding of the "floating chassis" idea.

Perhaps I wasn't as clear as I should have been.

The total PSU voltage is 220V and neither the -ve nor +ve is earthed. The anodes of the valves are connected to the +ve side of the PSU and the cathodes to chassis. The -ve side of the PSU is connected through resistors to chassis, and the -ve bias for the vari-µ valves is taken from points in the -ve side potential divider to provide the bias for RF gain adjustment. The chassis is earthed, or should be. One side of the 6.3V supply is connected to chassis and earthed.

The HT +ve side will be say, about 180V+ w.r. earth and the -ve side about -40V with RF gain set low. As the RF gain is increased ( the bias to the valves made less -ve ) the valves draw more current and HT+ to chassis will drop to say, 170V+. The PSU is still delivering 220V and the -ve side will now be -50V w.r. chassis.

It's a similar arrangement to that used in other sets such as the AR88, except that in an AR88, there was a built-in PSU and there's mainly no need to think about it. With 1155s you have to have an external PSU and it's easily assumed that means 220V + and earth, the earth being connected to the chassis.

Without thinking about it much, I suppose you could use a +180V, -40V and earth supply, but it's more complicated, it wasn't the way the set was designed to work, and a floating 220V supply fits the bill very well, so why do it?

HTH

Pete.

[Enthusiast]

The aim of my first post in this thread was to establish whether a recent step-by-step guide to restoring an unmodded 1155 existed and - if not - to suggest that one or more Forum members who have 'restored' an 1155 to safe working order (excluding D.F. function) might fill the gap with such a guide.

I think we've established that no recent step-by-step guide exists - and 2000 plus views in less than two days (a record?) suggest there is - at the very least - 'interest' in providing one.

I believe such a project is possible - but only if a clear editorial plan (what to include and how to present it) is combined with the technical expertise of members like Sean and Pete.

A sensible first step - as suggested by Mike - would be to begin by using the technical expertise of Froum members to devise a simple-as-possible circuit for an expternal mains psu plus small audio amp driving a speaker to be plugged into the P1 of an 1155.

Such a circuit (useful discussion has already started - whether to use a pair of rectifier diodes with an LM386 for the audo amp, rating of transformer etc) could be presented in the form of a step-by-step construction project.

By step-by-step, I mean supplying the instructions you might find with a PW construction project - aimed at people able to use a soldering iron amid home work-shop surroundings with enough knowledge not to be a risk to themselves or others.

Instructions could include:

List of components available nationwide via outlets such as Maplins or via a specialist supplier - as I pointed out and Pete confirms, the mains transfomer will be the hardest item to source.

Chassis details - ideally ready-made from Maplins or similar - with drilling instructions for mounting transformer, amp board , on-off switch, aerial connection etc

Drawn component lay-out for the chassis - imnportant since translating a circuit diagram into a practical component lay-out is one of the biggest hurdles faced by less experienced would-be constructors.

An explanation in crystal-clear language about how the psu/audio amp works - and the considerations needed in its design for the particlualr requirements of the 1155.

(I fear the exchange between Mike and Pete on earthing /bias arrangements on the 1155 would need to be simplified.....)

As I've said in a earlier post, finding a commercial source for a mains transformer (I agree that 6.3v at 3 amps will be enough for the LT without D.F. valves with 220v (or even 200v) for HT) might be difficult. It's important that the design uses readily available parts - ie not relying on cannibalising radio-grams or the like...... Can anyone suggest a commercial source?

Is this start to the 'Guide' project really an impossible dream?

Once achieved, it would pave-the-way for detailed discussion of what to include in a step-by-step guide to restoring an unmoded 1155 to safe working order.... using modern, easlily available components.

I'm sure there are enough of the 80,000 plus 1155's made in this state to make the 'Guide' worthwhile ....


David

PS It would be good if more of the 2,000 plus viewers re the thread thought about reasons for the #'Guide' instead of reasons to do nothing .....

[Sean Williams]

David,

You mention "an unmodded 1155" as the target audience for this book.

I would think over the last 10 years I have handled or seen aroud 250+ R1155s, and of these, I can only remember 3 that were original.

Any guide will have to include a whole section dedicated to getting the set back to normality - given the scope of butchery advocated by publications over the years this would entail anything from refitting the odd valve, right up to the complete rebuilding of the set from the chassis up.

Not a section I would care to comment on!

There is a good reason the step by step guide does not exist - the R1155 is not a nice set to work on if you are not familiar with its oddities!

Forget Maplin Chassis - they are too flimsy to support a decent power supply.

Transformers are available from Sowter, not cheap, this is why most enthusiats cull them from other equipment.

Not a simple project.

Oh, I wouldnt give too much credence to the thread views - when you do a google or msn search the bots add to the page views.

Sean

[Enthusiast]

A few misunderstandings, Sean......

I use unmodded in the sense that building a mains psu/audio amp as a first step would only make sense in relation to an 1155 (like mine and Mike's) that have not been retro-fitted with an internal mains psu/speaker output stage.

I'm not suggesting the 'Guide'; be used to restore 1155's to original spec - that would be crazy..... If I was, I wouldn't have suggested an LM386 audio amp or not bothering with the DF stages.

The Guide would be written for use in assessing/testing/fault-finding any 1155 - modded or not...... The most common mod has been fitting an internal mains psu and output stage - and the Guide would be useful to owners of these wanting to carry out intital tests/assessments to long un-used receivers with a view to replacing caps, wiring etc

We can argue until the cows-come-home about the number of (largely)unmodded 1155's still left - but they do come up (albeit sometimes fetching inflated prices) on E-bay and I know of at least half-a-dozen with owners crying out for a check-list guide. It's also reasonable to assume there are numbers still awaiting re-discovery in house-clearance and the like (the way my 1155L turned up...) But this - see above point - is a red-herring re the need for a 'Guide'.....

Believe me, Sean, the need for a Guide is out there.....

Think positive - it's the only way..........

David

[XTC]

If you have an 1155 with an internal mains PSU, the checks you need to do are in essence the same as for any vintage radio.

See here:

http://www.vintage-radio.com/repair-...and-tests.html

The big difference is that you are not dealing with something professionally made, which you can assume was sound when it was built; you're dealing with something which could be a dangerous bodge, or which was not well designed in the first place, or possibly something which was never finished or which has never been powered on.

Domestic radios almost never have the kind of codging ex-military sets often have and the 1155 being a cramped dedicated airborne set was subject to more codging than almost anything else. Furthermore, 1155s are not easy sets to work on.

See this thread concerning the problems with removing the tuning cap.

https://www.vintage-radio.net/forum/...highlight=1155

With most sets, removing the tuning cap wouldn't present much of a problem.

I designed the regulated PSUs, one for 1155s and another for a PCR, partly because I have a preference for regulated PSUs, and partly to take advantage of components I had available or came across at rallies for a reasonable price.

To produce a design anyone could build from readily available parts would involve finding sources of:

A suitable new case, probably £15 or more; mine cost 50p and a quid. One was for an American airborne ATU and the other was just a suitable case with a homebrew PSU in which looked decidedly dangerous. Maplins don't do anything remotely suitable.

Suitable transformer, I suppose there are new ones available, but they would be £50 or more.

Heatsinks, probably £5 and a method of mounting them safely. My heatsinks are ex-equipment, I'm happy with the way they are mounted, but they are live at over 400V DC.

If I'd had to buy these things new, I wouldn't have done it.

So, if anyone wants to take this route, I'm happy to provide pictures and a cct diagram and explanation, but apart from that, anyone wanting to do a similar thing is more or less on their own and doing things on their own responsibility.


Pete.

[pnh0001]

Fellow R1155 enthusiasts

I have been working on an R1155 rebuild guide for some time now as I strip down and rebuild my B model. It was complete with all the DF section (which I want to get working). I have stripped it down to a bare chassis and front panel and am now rebuilding.

As I go along I have been producing wiring schedules, circuit board diagrams, photos of what goes where, enough to be able to completely rebuild any R1155 from a pile of bits.

I still have a way to go, basically I have plans & schedules for wiring of V5 - V9, including DF components inside the BFO box (assuming of course you have things like the coils that went in there). The tagboard inside the front LHS and its wiring to the rest of the receiver is all done, as is the tagboard on the end of the coil box.

What I still have to do is the coil box - quite a major undertaking. Before I started that I was going to get to the stage where I could put power on and inject an IF signal and see if everything was working at that stage.

My plan was to self-publish a 'how to do it' book and sell it for a modest amount. I doubt it would cover my cost in hours of time. It looks like I should get a move on!

I have a bit of journalistic form in this area having written up my RA117 rebuild. See www.peterholthamswriting.blogspot.com.

cheers

Peter VK4COZ

[MichaelR]

Hi Peter,

Fascinating work. Do you use the Racal ?

I like the complete strip down that you are doing with the R1155. I have done this with an HRO which is a much simpler unit to work on.

My plan is to build the external power supply and audio amplifier. I intended to then work my way backwards on the rebuild of the set, testing at each completed stage.

From your experience is that feasible

regards
Mike
G0NEY

[dave walsh]

Looks like you are the man everyone seems to be looking for Peter! I'd certainly buy a copy! "Enthusiast"s determined approach may have paid off.
As they say, "if you don't ask you don't get" although most of us perhaps assumed that there was nobody around with an answer. It would be a great service to restorers if you could produce this guide but I suspect that it might even be read by people who didn't have a set. The other other route I had thought of was for Enthusiast to have a go himself with group support but you seem very well advanced already. I'd seen your RB articles but not connected you with this project so it's good of you to step into the spotlight. Could be like a tail-gunner in the Lancaster though!

I was compiling a bit of a list of the articles/hints, tips and conversions over the years [inc the classic W World post war ones] PW/SW etc and other restoration accounts of the type now deemed indequate for purpose-there are a lot of them. Perhaps something like that would make a companion volume to a definitive "ground up" description? Even more work though! Best Wishes. Dave W

[Enthusiast]

At last! From the shadows of far-away Australia, steps forward Peter (Pnh0001) - the man combining positive can-do-attitude with hands-on expertise who Mike, Dave and I ( plus many other 1155 fans) have been seeking.....

Put me down for a copy of any book you write - in the meantime, why not approach the Editors of radio magazines like PW (or even Radio User or Radio Monitoring) who might commission articles on your progress so far?

Astonishing viewing figures for this thread prove that you are onto a publishing winner - go for it!

In the meantime, please keep the Froum up-to-date with your 1155 progress.

I'll be a regular visitor to your blog in the hope that you write-up your 1155 experiences.

Very best wishes - and good luck with the re-build.

David

[dave walsh]

It is good news David but steady on . It's you "who" is "The Seeker" [Who Reference]. Personally I woudn't have pushed so hard but I'm not complaining! It's a good outcome [just on the info revealed so far]. You can't assume everyone is quite "on the same page" here though, in the same way that 2k hits might not mean exactly what you think it does but I agree that there is certainly an extraordinary level of interest [apparently]. I'm still wondering why? Must be the war time factor surely? I'm not being negative, just measured. Clearly Peter in Oz could do a fantastic job if he is willing.The only downside could be even more 1155 demand [initiated by you] but the current financial climate could help with that I suppose. Cheers Dave W.

[Enthusiast]

Dave, I assumed you included yourself in your phrase "Looks like you are the man everyone seems to be looking for Peter!"


But apologies for taking your name in vain........

And yes, Peter (if willing) is the man to produce a Guide. I hope others on the Forum will give him maximum encouragement.

Over to you, Peter - and, to repeat, well-done mate!

David

[pnh0001]

R1155ers

I am glad people think a guide might be useful, and I will continue to push on with what I had planned. Don't expect it that soon, it's a major task and I still have a lot to do, but I can get a couple of days a week at it, depending on whether the global financial crisis forces me back to full time work or not.

I have attached a jpg file (lowish res to keep it small for downloading) showing the sort of thing I am doing. It is what I have called the 'bias tag board'. It fits inside the front LHS of the receiver. This is just the component side, I have also mapped the back where there is some wiring. The board can be wired to the receiver by referring to a wiring schedule I have drawn up for each of the numbered wires. I have also chopped the relevant part of the circuit out of the full diagram, then shaded the components on the tag board so you can see where things go on a separate figure.

There are also issues about the order of rebuilding, for instance, this tag board is wired to what I have called the '9-way tag board', as well as L30 the output transformer and elsewhere. It appears as far as I can see, the manufacturers must have left long enough wires dangling from the 9-way to get them to the Jones plugs and elsewhere on that side of the receiver, as well as prewiring L30, the Het On switch etc etc.

These things I want to sort out so nobody else builds a stage, then has to unsolder bits to get other parts wired.

I have done similar drawings for all the other tag boards, as well as the valve base wiring etc.

Comments? Is this a useful way to go?

cheers

Peter

[MichaelR]

Hi Peter,

This is exactly the detail required. I Rebuilt a Bendix transmitter about 15 years ago. Was I glad that I took photographs and labelled wires. The wiring harness would have been a nightmare to put back, the effort in this detail is saved in the long run by the lack of errors.

I suspect also that the performance of the set will be compromised if wiring is not positioned near to what it was originally. Pickup and feedback needs to be considered.

Good Job

Mike

[G4XWDJim]

I believe there is a 'Bench Wiring Diagram' available as part of the Air Ministry Air Publication AP 1186. I've never actually seen it but have seen ones for other sets and if they're anything to go by every wire routing, earth point and component is shown in the order of connection which of course may be quite different from the way they are drawn on the circuit diagram. I don't know where to get one I'm afraid. vmars don't have one I'm sure but it must be worth trying to find one.

Jim

[dave walsh]

Peter's tag board example shows that whatever he produces will be both ideal and well worth waiting for! I didn't know about the Bench Wiring Diagram Jim mentions but clearly, more interesting info is emerging all the time [whether it informs Peter's project in the end or not]. It's a bit like Time Team really -is that shown in Oz? Dave W

[MichaelR]

Thanks Jim,

I will try and see if I can get that to share.

Regards
Mike

[John H.]

Hi Peter, (pnh0001).

I have the original bench wiring diagrams, point to point wiring routing and harness make up for chasis topside and chasis underside, dated December 1940, not found in AP2548 etc. As noted by Jim above.

These are crying out to be formatted in the way you have illustrated. They show much detail and concise positioning of wiring runs etc.

PM me if you think they may assist with your project. They could save you re-inventing the wheel, so to speak.
Regards , John.

[kenn1946]

you are correct regarding the supplies. The psu needs to output a single 220 - 250volt supply - NEITHER line connected to earth. the minus 30 is derived across a resistor network within the receiver.

if a valve output stage is built, it must be fully floating - ie nothing connected to earth - using the negative line as a ground for the AF

Failure to observe this will upset the receiver bias