Wireless Set No. 52 Canadian - Project

[David Dunlop]

I sent a copy of my testing results to Jacques Fortin the other day and he provided me with some very useful feedback.

First, he pointed out I had missed a couple of resistors in the V1J and V5D circuits I was looking at (R29B and R47C). I am on the hunt for them now and will report back on what I find.

The second issue he brought to my attention was regarding the results for R12A and R31D. Both of these resistors were quite different from one another but both tested 8 Ohms. I thought that was odd at the time…end of story. However, Jacques brought to my attention something I had missed in the Circuit Diagrams.

These two resistors are both serving as Feedback Voltage Dividers: R12A on the Primary of Transformer T2A and R31D on the Tertiary of Transformer T3A. As such, they are wired in parallel in these two circuits, so it is not possible to get an isolated Ohms reading from them just by putting your VTVM probes either side of the resistor body. In doing so, the meter reading is biased by the transformer. You need to disconnect one end of the resistor from the circuit involved to get a pure reading of the resistor. Both of these resistors are a bear to get at, so I have decided I will simply replace both resistors outright. Do tricky work once and be done.

The other really nice bit of information from Jacques, was that he took the time to document the best current resistor equivalents that I could use to replace each of these older components. This was something unexpected, but invaluable for me. I simply do not do enough regular electronics work to be comfortable substituting modern resistors for older ones. Bumping up the wattage rating to get a resistor of correct Ohms is one thing and I have done that just fine in the past with 1/4-watt resistors. Modern ones look way too small in a piece of vintage electronics and the leads are always far too short to cover the distance between Panel Tags in a 52-Set in any event. But I am just not comfortable going to higher Ohms ratings for any given circuit. I worry too much I am going to buggar things somewhere down circuit.

Other than that, so far so good.


David

[David Dunlop]

I was able to find the two remaining resistors Jacques had mentioned to me, fairly easily. I must be getting used to tracing the components finally.

R39B is located on the rear end of the Sender Tag Panel AS, which is located on the inner right skirt of the sender chassis. R47C sits right at the end of the Microphone Jack assembly. Photos attached. The test results for both are as follows, following the same convention as my earlier posting for the first 10 resistors:



R37B, 15,000-2, 20, V5D Plate feedback Limiter, Tested 15,960 Ohms
R47C, 50,000-1/4, 20, V1J Grid Voltage Dropping, Tested 58,200 Ohms


Both of these will be replaced.


While I think of it, Sender Tag Panel AS, in the Illustrated Parts List for the 52-Set is actually, PANELS, Phenolic, 12-Tag ZA/CAN 4224.


David

[David Dunlop]

I now have a list of current suitable carbon composite resistors to replace the ones I have found so far needing such attention in the Sender. Finding ones I can actually use in restoring the Sender is shaping up to be a very big challenge, and the fact it jogs me back to the same issue I had when replacing resistors in the two receivers is not helping.

Working on any of the smaller Tag Strips, or the valve sockets, is not a problem. Even the smaller Tag Panels can be worked with, but it is the larger Tag Panels which are a problem. The tag spacings on these panels are either 2.25 inch for the smaller ones or 2.5 inch for the larger ones. When you start looking at replacement, new production, carbon composite resistors, you quickly find the sum of the lengths of the resistor bodies and the two axial leads seems to give a modern standard length of 2.38 inches. So with a lot of careful dicking about with an easily accessible Tag Panel, you can just fit a new resistor across the smaller panel, but are SOL doing so with the larger Tag Panel. Most of the resistors currently needing attention are, of course, on a large Tag Panel. I am a bit of a way from getting the capacitors sorted, but suspect I am going to run up against the very same 2.38 inch overall length limit with them.

There are a few companies out there dealing with fairly extensive NOS supplies of carbon composite resistors but none (rightly so) guarantee the specs of the components anymore, and using them for jewellery purposes seems a common theme.

About half of the resistors I am looking for are also used in the receiver so I could hunt them down for testing and reuse, but if they are not installed in Tag Panels currently, it is very likely their leads have been trimmed too short to be of use, even if solidly on specifications.

So the Sender sits on the bench while I ponder the situation.



David

[David Dunlop]

It is interesting how simple little things can bring a big project to a halt.

The valves from the Sender are all neatly packed away on a corner of my work bench and the Sender sits quietly covered up to one side, while I try and sort out finding replacement Carbon Composite Resistors that I can actually work with in the 52-Set restoration.

The problem is with the modern overall length of new resistors (lead, body, lead). Turns out wartime manufactured resistors of this type had an overall length of about 3.4-Inches. With the two main sizes of Tag Panels used in the 52-Set having tag spacings of 2.25-Inches and 2.50-Inches, this component length was ideal. What I have been finding in the modern market are most overall lengths coming in at 2.38-Inches, so you can quickly see the road block.

On the bright side, some international inquiries have resulted in leads trickling in (yes, there is a pun there) of a few suppliers about with Carbon Composite new made resistors with overall lengths close to 3.0-Inches. I may have to go to higher wattage ratings than the original resistors to get ones that will fit, but that will not affect performance at all. It is just all very time consuming.

And there is yet another wrinkle in the T-shirt. To replace all the resistors currently identified as needing it, two of the Tag Panels must be removed from the sides of the Sender chassis to better expose the tags for working on and these panels hold nearly 10 capacitors that need to be tested. I cannot reach the back terminals on any of them for testing at the moment and I know a few of them will be toast. Adding to the excitement, a few of the capacitors will have to be removed to expose resistors tucked behind them that need replacing. So a whole bunch of adventures are currently hurtling down the side roads towards the main highway and I still have not finished reading the road map!

There is an interesting curious side to all this, however.

Since I had carefully disassembled the spare Receiver I had on hand, I decided to check if any of the resistors I needed to replace in the Sender, might also have been used in the Receiver and test them for possible use. There were a few, but all were installed in locations where, if carefully removed, their leads would have been far too short for reuse in the Sender in any event. But something interesting in the way the Canadian Marconi Company arranged the parts lists in the Working Instructions Manual for the 52-Set unexpectedly popped up when you looked at long lists of the same component.

It is common practice for companies to list specific parts in ascending order of their electronic specifications. For example with resistors start with 1/4-Watt and within that group list from lowest Ohms value to highest. Then go to 1/2-Watt and repeat. And so on. Same process for capacitors. CMC took this organization one step further. They have a column in the parts lists that identifies which component the parts are used in and I discovered when looking at the larger lists of identical parts, CMC always listed the components in the following sequence of first to last:

R: Receiver
CC: Crystal Calibrator
S: Sender
SU: Supply Unit

So if you look at capacitors in the C3- series ( .1 uf, 500 Volts, 20%), there is a lot of them. C3A to C3Z are all found in the Receiver. C3AA to C3AF are found in the Sender and C3AG to C3AK are in the Supply Unit.

At the other end of the spectrum, C32A ( .01uf, 500 Volts, 20%) is in the Sender and C32B in the Supply Unit…end of list for item.

I do not know why CMC adopted this convention in the parts list found in the 52-Set Working Instructions, or even if they did it in other products as well, but at least I now am aware that any future components in the Sender I find with a Circuit Reference Number ending in ‘A’ will definitely not have a spare lurking in the Receiver or Crystal Calibrator.


David

[David Dunlop]

One of the nice things about a project this size is that there is always things you can accomplish when work stalls somewhere else.

That is the current case with the component replacement work I ws doing with the Sender. It is going to take a while to source all the required resistors and capacitors I need to hopefully solve the majority of issues around valves V1J and V5D and all the bits need to be replaced at the same time. So I have returned all the valves to the Sender and the Sender to the Carriers No. 4 until such time as I have all the needed resistors and capacitors on hand.

There is a trick to getting the three main components back into the Carriers No. 4 easily. If you do not keep the chassis you are putting back completely square to all side of the Carriers No. 4 as the sockets on the chassis engage the plugs at the back of the Carriers No. 4, they will bind up and it is a royal pain in the butt to get them apart. The Sender slid in so smoothly this time, I almost thought something had gone horribly wrong.

So the part of the project I moved over to was a little painting detail on the hammer that is part of the tool kit for the Wireless Set No. 52. The original hammer was a ‘BULLDOG’ product, from what I can make out on the decal in the first photo today. A pair of tool companies show up in researching this name, one in England and the other in the United States. A few old photos of corporate logos show up, but none so far of that elongated diamond decal in the illustration. The hammer I found for the tool kit is not made by Bulldog and the handle length is about one inch shorter than the original tool specifications, but on the plus side, the handle is the correct shape, clear varnished hickory and the head is the correct weight and style; the second attached photo. I had no idea there were so many different styles of ballpane hammer heads until this project arrived in my lap.

I may never find a good condition original hammer for this project, so decided to replicate the look of an original with what I have on hand. The most obvious feature is the black end on the handle, but the top end of that feature has a distinctive angle to it. Practice as I could, I was not able to get that good a look with any kind of tape rapped around the handle. You are trying to keep a straight line around an oval cross section that is narrower at the top than the bottom of the angle. After months of ruminating over this, I finally had my ‘Eureka Moment’. If the end of the handle was dipped into paint at the correct angle, to the correct point on the handle, mission accomplished. But how does one keep the handle perfectly steady? A few days of thinking about that …and then I realized, you fix the handle and move the paint can.

I did have a one quart can of gloss black enamel on hand that would work, so that was a start. The next step was to get reference points onto the front and back faces of the handle to pinpoint the two ends of the upper angled paint line. I was able to scale these two measurements off the illustration and proportion them, with some basic High School Math, to the shorter handle I was working with and transferred these two reference points to my handle; the third and fourth pictures.

So far, so good.


David

[David Dunlop]

The next step was sorting out fixing the hammer I had in a stable correct position to work on. My portable bench vise came in handy here. The first step was to fit a small strip of oil board over each jaw of the vise to avoid marking up the head of the hammer. I then fit the hammer into the vise just firmly enough I could still move it back and forth in the jaws. Also checked to ensure the handle was dead vertical to the floor.

I could then set the vise close enough to the edge of the bench the hammer sat freely out of the way. With the help of a spirit level, I was able to adjust the hammer handle until the two reference marks were dead horizontal. Photos 1 and 2 here.

With the paint mixed, off came the lid and a quick check confirmed the level of the paint was low enough that it would not spill out as the hammer handle displaced the paint when immersed in it. Since the paint was a liquid and seeks its own level, I really only needed to reach the top of the reference mark on the back of the handle to get it right, but I had to raise the paint can slowly enough to allow the meniscus to just come up the the required point and then lower the can back down.

There were a couple of points to consider now. Most important was the handle is at an angle now and all the excess paint is actually draining towards the front and bottom corner of the handle. That is OK for a short while as that means the excess paint is draining away evenly from the angled line you have just created, and you want that initially.

I held the paint can under the handle until the steady flow of paint ceased and the subsequent drops became infrequent and made sure a pile of rags was on the floor directly under the handle. At this point, the paint is still going to flow down the handle slowly, but you now want this to flow evenly around the entire handle so the thickness of the final paint layer is even around the entire handle. That means slowly moving the hammer handle back to a vertical position; the 3rd photo. At this point, I used paper towel to draw off excess paint from the very bottom of the handle, several times over the next hour, to reduce a ridge accumulation of paint around the bottom rim of the handle as much as possible.

24 hours later, the paint was dry and I was able to remove the hammer from the vise. I am quite pleased with the result in the last photo. A bit glossier than the varnished areas, but a little careful rubbing down after the paint has hard cured in a couple of weeks, will solve that problem.

If I ever do find an example of the original BULLDOG diamond decal to work with, I am also going to have to add a small black paint and metal stamped ‘R’ to the side of the handle to clearly ID it as a replica.It is what it is, not what somebody might want it to be after I am all dust and ashes.


David

[David Dunlop]

Finally caught up on another little task this morning; getting the stencils back onto the Reels, Cable No. 2 Mk II for the 52-Set.

These reels are identical to the standard, similar reels of this type issued by both the Canadian and British Armies, but like a number of the items Canadian Marconi Company issued with the various 52-Set Kits, they ordered a number of reels directly from a manufacturer, and a CMC Part Number was added into the stencils for these items.

Since the stencils applied to the similar, but more robust reels used with the Aerial 4-Section that came with the 52-Set, were sprayed in a fairly light coat of flat white paint, I decided to go with the same process for this cable reel.

The first step was to trim down the two stencils I had made last year, so they would fit properly on either side of the hub assembly on the free end of the reel, as per the reel used with the horizontal aerial. Once the two stencils were properly trimmed and taped down, I masked off all the exposed areas on the reel with newsprint and applied several light coats of flat white spray paint from a height of about 18 to 20 inches and let the paint more or less float down onto the reel, to minimize any excess spray getting driven under the oil board. It took a few careful passes from several different directions to get a paint density comparable to the original markings on the aerial reel, and 20 minutes later, I was able to remove the stencils and found no trace of overspray anywhere.

Nice to have one more part of the project out of the way.


David