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Old 13th Jun 2022, 10:23 pm   #41
jamesinnewcastl
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Default Re: Standard Beam Approach - Rebuild update

Hi Adrian

The simple answer is that I don't know if they will 'cook' or not! I tried to work out the power that would be dissipated from a study of the circuit and often found it was nowhere near the capability of the resistor.

The attached pic shows my other 'new' components including new 'dog bones' made for the marker receiver. None run hot and I've had the unit working for hours on end.

But, it depends on the dissipation that each circuit demands. It is probable that the leads provide a cooling path and you can't eliminate the plastic as a means of heat loss too.


Cheers
James
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Old 13th Jun 2022, 10:31 pm   #42
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Default Re: Standard Beam Approach - Rebuild update

They look good, will have to look for some 2 watt resistor packs and see if I can do similar for my 1/2 watt ones that need replacing.

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Old 6th Sep 2022, 6:43 pm   #43
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Default Re: Standard Beam Approach - Rebuild update

Hi All

Slow progress (due to doing other things...) but there is movement!

Firstly I have stripped the whole Main Receiver down to its parts. See Pic. This is easy of course except for the nuts that had seized. The chassis needs cleaning, especially to rid it of 'that smell'. For this I am splashing out on a Soda Blaster, not so much the soda or the tool but the air compressor that is needed. I'm hoping that it will take off the paint too.

The workers that made this item must have had a really devious assembly plan as there are many solder joints that are hidden deep in the weeds and the only way that I can see to rebuild it is to put flying leads on every thing before fitting the item onto the chassis and putting the next part on top virtually entombing it!

I am reverting the design from 'C' back to A. Hopefully I'll be able to polish out the 'C' scraped onto the name plate. I am building it to A as that would have been the version on my aircraft of interest and because I have the documentation for A!

Cheers
James
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Old 6th Sep 2022, 6:56 pm   #44
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Default Re: Standard Beam Approach - Rebuild update

Hi, some more...

I'm replacing all the dodgy or potentially dodgy components with new 'look-alikes'.

I've posted the usual restuffed capacitors but I am now tasked with replacing the resistors of the type that came after the dog-bone ones in the Marker Receiver that I did earlier.

So, I have obtained some plastic tubing and painted on plastic primer and body colour - see pics. To paint the stripes I simply held the bodies on a drill and touched the rotating body with a paint brush.

I'm sealing the ends with a wood filler that is almost exactly the right colour out of the tin - great but the resistors are small and don't fill the tube so I have an issue that I can't put the filler in as the resistor would move. Incidentally the white resistor in the pic is just a trial - the resistor would go in the painted item.

Also the resistor in a plastic tube isn't great from a heat dissipation point of view. Actually there would be an air gap and then a plastic tube. I'm going to get rid of the air gap and hold the resistor concentric by wrapping a thin layer of copper tape over the body of the resistor. The right length making a tight fit and two problems are fixed!

Of course I have now lost the air gap between the leads but I don't believe I will have much of a problem. My ultimate issue may only show up when I power the thing up. Arcing and melting resistors take one step forward!

So now I need to make a full set of components!


Cheers
James
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Old 6th Sep 2022, 10:51 pm   #45
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Default Re: Standard Beam Approach - Rebuild update

James,
Are there no newer styles of resistors which would look the part if repainted? I'm thinking of the film types sold by the likes of RS (made by Piher?) in the 80's. They came with maroon or beige or green bodies in various power ratings.

Andy
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Old 7th Sep 2022, 11:20 am   #46
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Default Re: Standard Beam Approach - Rebuild update

Hi Andy

I've looked up that resistor type and it has a bulge at each end and is 'thinner'. Also I would need to paint it and I could not use the 'spin it' method without taking much care in the chuck. With the current method the painting is easy. To be honest I have actually looked for an equivalent!

The big drawback with the curent method is that the sealing of the end caps is going to be messy and slow. Also the filler hardens and goes unworkable very quickly which means many 'small' batches. I'm currently seeing how little hardener is required for slow setting!

Cheers
James
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Old 28th Oct 2022, 11:04 am   #47
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Default Re: Standard Beam Approach - Rebuild update

Hi All

All the original components I'll be using have now be cleaned. All solder joints re-soldered. New components have been 'made'. So now I am ready to start the rebuild!

The following pics show the parts. I have reused the waxy cap ident sleeves to maintain more originality but I believe that they would have been white at first, rather than yellow.

Happily the main connector is NOS and really in good condition - sadly I don't have the mating part!

Since I am reverting a receiver that had been converted to the 'C' variant back to it's original 'A' variant there are a few component changes. One notable one is a 4 x 2uF capacitor which had been replaced by a smaller one with only 2 x 2uF. I've gutted that one, drilled the base to take 4 off HV feed thrus fitted 4 x relatively tiny electrolytics and sealed the end that originally had the connection pins. Resprayed and re-annotated.
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Old 28th Oct 2022, 11:08 am   #48
M0FYA Andy
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Default Re: Standard Beam Approach - Rebuild update

The resistors look very authentic!

Andy
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Old 2nd Dec 2022, 10:43 am   #49
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Default Re: Standard Beam Approach - Rebuild update

Hi All

The main receiver is now 99.9% complete, the attached pic shows before and after. Since I've reverted the circuit to the original 'A' version there are differences. 99.9% of the wiring is new.

Next task is to power the unit up - using the original PSU motor generator.

One regret is that I didn't put new white labels on the capacitors having noticed that they were in fact white as shown on a photo in the AP.


Cheers
James
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Old 5th Dec 2022, 8:16 pm   #50
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Default Re: Standard Beam Approach - Rebuild update

One thing to beware of, James, with your wrapping a resistor up in copper tape idea - is that you will effectively be building a small capacitor in parallel with the resistor. You will thus change its RF performance.

Will that matter? In many circuit positions - absolutely not. Obviously resistors like anode and screen droppers which are not live at RF will not be affected at all. Resistor in RF live circuits might be given that are talking 10s' of Mc/s here. Sometimes such changes in passive components can be "tuned out" by a slight adjustment to trimmers etc.


Richard



Quote:
Originally Posted by jamesinnewcastl View Post
Hi, some more...

>>Snip>>

Also the resistor in a plastic tube isn't great from a heat dissipation point of view. Actually there would be an air gap and then a plastic tube. I'm going to get rid of the air gap and hold the resistor concentric by wrapping a thin layer of copper tape over the body of the resistor. The right length making a tight fit and two problems are fixed!

>>Snip>>


Cheers
James
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Old 5th Dec 2022, 8:21 pm   #51
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Default Re: Standard Beam Approach - Rebuild update

Like Andy, I'm very impressed with the attention to detail that you are demonstrating. I've not seen "refurbished resistors" looking that authentic before. Indeed, I've not heard of anyone actually attempting to produce realistic looking vintage resistors before, but this is the level of detail that we need to make a convincing "as original but working" example of historic equipment.
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Old 6th Dec 2022, 1:04 pm   #52
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Default Re: Standard Beam Approach - Rebuild update

Hi Richard

Thanks for your comments. The resistors will soon be undergoing the two tests, will they (some) melt and will the additional capacitance be an issue? Along with, of course, will any of it work?

Currently I am building up the test rig around the receiver. I need the control panel, indicator dial and power supply to be mounted and wired in.

I'm not familiar with valve circuits (or radio come to that) and I note that this design has an HT supply that connects between the anodes and a line called 'bias resistors', not earth (what I would call 0V common). I had originally thought to ask a question about this on here but decided after some thought that this is how it was intended to be and not just a mistake in the documentation. So it seems that the HT supply negative will fluctuate below 0V common in order to supply the negative bias for the valves - this value being controlled by the AGC requirements of the circuit. The AGC for this system being switched ON when flying generally and looking for the airfield and switched OFF when on the final glide and using the actual field strength to guide the pilot down.

I was OK with this until I looked at the HT supply of a later system to see the HT supply connected to the 0V! Sadly I don't have the receiver circuit of this later system so I can't see how they are generating the bias.

In any event I will have to suck it and see!

I'll post the results when I get them!


Cheers
James
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Old 6th Dec 2022, 1:30 pm   #53
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Default Re: Standard Beam Approach - Rebuild update

James,

the usual way bias is generated is to disconnect the HT- connection from the dynamotor from 0V and reconnect it by a "bias resistor". The entire HT current for the unit then runs through this resistor generating a -ve voltage for bias.

The bias resistor can be located in either the HT PSU, or in the receiver - it doesn't matter much which.

Its hard to say any more on this without the actual schematics, which will give bias resistor location and value.


Richard





Quote:
Originally Posted by jamesinnewcastl View Post
Hi Richard

>Snip>>
I was OK with this until I looked at the HT supply of a later system to see the HT supply connected to the 0V! Sadly I don't have the receiver circuit of this later system so I can't see how they are generating the bias.

In any event I will have to suck it and see!

I'll post the results when I get them!


Cheers
James
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Old 6th Dec 2022, 2:12 pm   #54
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Default Re: Standard Beam Approach - Rebuild update

Hi Richard

Good to know that the biassing arrangement is a standard way of doing things. Not all the valves are biassed like that, I assume that their function isn't affected too much by the HT changing a little.

For your information I've attached a redrawn and amalgamated circuit diagram (a little more to do!). I find that I have to redraw circuits as my brain needs a more structured presentation!

In the diagram the different colours represent different LRUs.


Cheers
James
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Old 6th Dec 2022, 3:08 pm   #55
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Default Re: Standard Beam Approach - Rebuild update

Here are pics of the Pilots Control unit which I refurbished a year or so ago. There were never any bias resistors in here so the later designs must have been quite differerent!

Cheers
James
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Old 6th Dec 2022, 9:13 pm   #56
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Default Re: Standard Beam Approach - Rebuild update

Hi James, looking good
Lots of Mil stuff (1154/55) used this trick to provide a bias voltage, often had a cap across the resistor for smoothing.
Connecting HT - to chassis can cause all sorts of problems and damage valves etc.

Cheers, Ed
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Old 9th Dec 2022, 9:55 pm   #57
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Default Re: Standard Beam Approach - Rebuild update

Quote:
Originally Posted by Ed_Dinning View Post
Hi James, looking good
Lots of Mil stuff (1154/55) used this trick to provide a bias voltage, often had a cap across the resistor for smoothing.
Connecting HT - to chassis can cause all sorts of problems and damage valves etc.

Cheers, Ed
Hi Ed

The big capacitor in the design is that very cap - it's even mentioned in the AP.

I've met another stumbling block in testing the main receiver. The same resistors are in fact housed in the Pilots Control unit. I only have the later version of this unit where they removed the Glide function (coming in on a fixed field strength line). The original unit switched between AGC and no AGC the new unit doesn't! Thus the bias resistors have disappeared from that unit and this explains why the later receivers connected all the cathodes to 'Earth'. Also all the pot values changed!

In the attached pics you can see that the pots are really very different from what you might expect. With no chance of finding any other such a device I decided that I might be able to 're-stuff' the existing odd pots. So I fiddled about trying to open then up and to my surprise and delight found that the pots consist of a casing and inside a perfectly normal pot! My cunning plan is now a more conventional re-stuff!!

I suspect that as the pot thread has a sort of rubber seal then this casing is intended to seal the pot from the effects of water/damp. A sort of waterproof casing.

Now I have to stop work on the main receiver and restore the control unit - again bringing it back to the 'A' version! Well almost anyway.

Cheers
James
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Old 4th Jan 2023, 5:41 pm   #58
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Default Re: Standard Beam Approach - Rebuild update

This is a fantastic project James, well done! I too have most of the system components but no intention of getting them working for now!
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Old 12th Jan 2023, 9:35 pm   #59
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Quote:
Originally Posted by 1155 receiver View Post
This is a fantastic project James, well done! I too have most of the system components but no intention of getting them working for now!
Hi 1155

Good luck with it! I know a man who has the original test 'oscillator' for the system but is hanging onto it! The only part that I have never seen is the antenna used to measure the transmitter field strength, oh and the ground based transmitter of course, that would be a find!

Cheers
James
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Old 25th Jan 2023, 11:12 pm   #60
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Default Re: Standard Beam Approach - Rebuild update

Hi All

As I can't get the types of 'Breeze' connector (socket) that I need I've produced a 3D print! The connector series all use the same outer shell and pins in various sizes so I can get sockets with the right shell size but the wrong insert. I've also modelled the two spacer rings. So making careful measurement I've made a 3D file and had the insert that I need printed!

As well as the insert, the cable guides and the 'backshell?', are also rare. I assume that these were the first things taken off and easily discarded.

Anyway, attached is a photo showing the shell and the original insert parts (top), the new printed parts are shown below with the new cable guide and backshell.

Amazingly the thread on the backshell fitted! With just a little forcing, which I assume was just cleaning the threads, the back shell went on readily!

Now I need to draw up some more inserts and also I'll be drawing the odd antenna connectors which I can't find in any form - I'll just make them!

I can get backshell printed in Aluminium but I suspect I will paint a plastic one!


Cheers
James
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