Wireless Set No. 52 Canadian - Project

[David Dunlop]

In my last post I mentioned some spin off work for the Slow Motion Tuning Drive turned up while I was replacing the Handles No. 72 on my Main Set Receiver.

I had noticed a while ago the Slow Motion Drive seemed a bit stiffer than it should have been to operate and when the Flick Control Lever to the right of the tuning dial was in it’s lower FLICK position, I needed two hands to turn the dial, which by rights should turn very freely with one hand with the control lever turned to that mode. My thought at the time was that since the Slow Motion Drive worked, but was very stiff, the problem was probably with one of the tuning shaft support bearings, fore and aft on the tuning condenser assembly. While working on the Handles No. 72, I decided to take advantage of the strip down and remove the large tuning dial to give it a proper clean. This necessitated removal of the Slow Motion Drive Assembly at the bottom of the dial. This is another of those tasks that can be intimidating because of the Bracket and Spring Assemblies No. C1 (ZA/CAN 0233) the Slow Motion Drive is mounted in and the fact there is a lower arm of the Flick Mechanism connected to the Slow Motion Drive one has to be aware of while removing and installing the drive unit. Again, this is another bit of work that you should let gravity help you with. Place the receiver on its back before you start.

The first two photos are of a standard drive and a Slow Motion Drive assembly. The stud on the lower right hand side of each it what engages into a large, self-locating V-Slot on the end of the lower Flick Lever. When everything is installed, and you turn the Flick Control Lever to the ‘FLICK’ position, the lower Flick Lever (which is spring loaded to keep it under tension, pushed the right hand side of the Drive Assembly away from the rim of the large tuning dial. The allows the operator to grab the Handles No. 72 and turn the dial rapidly to one of the preselected frequencies. When that position on the dial is reached, an Upper Flick Lever, coming from the Flick Control up to the two Indicator Flags Mechanism drops the appropriate Indicator Flag down for either the A or B Frequency being selected.

Because of the orientation of the Lower Flick Lever, and the fact it is under spring tension, if there is no Tuning Drive in place for it to engage, it will automatically swing to the left, across the small rectangular opening in the panel behind the drive assembly, when you remove the drive. Don’t look for it on the right side later. It won’t be there.

Before you start, make sure the Flick Control Lever is in its middle SET position and leave it there. First step it to remove the knobs from the drive. Then remove the long pivot screw at the left side of the Bracket and Spring Assemblies. It is a good idea to keep a thumb on the assemblies, just to the right of the pivot screw as you remove it. To keep everything in place until you are ready. You will notice as the screw comes out of the panel, the Bracket and Spring Assemblies relaxes and a small bend shows up along the lower edge. At this point, slowly lift the Assemblies away from the panel. About 1/8-inch away from the panel you should feel the locking stud, about ½-inch to the right of the pivot pin pop free of the panel. When it does, slowly move the Assemblies up and to the left at a shallow angle. You should notice the Lower Flick Lever following along for a while and then disengaging and swinging off to the left of the rectangular hole.

To replace the complete Drive, Bracket and Spring Assemblies No. C1, start by putting the long pivot pin in place to keep the two parts together. With a small little hook, retrieve the Lower Flick Lever from the left side of the little rectangle. As you move it slowly to the right, you will see the large V-opening appear with a rounded apex to the V. Insert the stud on the lower left end of the tuning drive into the V-opening, left the lever engage it and move the entire assembly into position such that the long pivot screw can be engaged in it’s hole and threaded home. The manuals will tell you to run the pivot screw completely home before the next step, but that just make the next step that much harder for you to complete.

The small locking stud to the right of the pivot screw rests very quickly on the top of the panel face. If you run the pivot screw completely home first, that small stud really digs in and you are making a lot more work for yourself. Don’t worry about getting the rim of the large tuning dial into its slot on the central pin of the drive assembly. If you miss it initially, it should pop into place as you tighten to pivot screw.

The last step the manual will advise you to do is insert a small slotted screw driver under the Bracket and Spring Assemblies, engage the end of the small locking stud and push it up about one half inch until it pops into its locking hole. I find a much better solution is to use a thin steel putty knife as shown in the third photograph. If you have to, remove any switch knobs in the area to make things easier for you. I usually tighten the pivot screw down just far enough I can slide the putty knife blade under it easily. The really nice thing about the putty knife is it has a wide blade and you will not miss finding the small locking stud. That spring on the Bracket and Spring Assemblies No. C1 has a surprising amount of tension in as you move it closer to its panel hole. The bottom edge of the assembly should be perfectly straight when you get to the hole. Once it has dropped in place, remove the putty knife, finish tightening the pivot screw, reinstall the tuning knobs and any others you had to remove and you are good to go.

Sorry for the length of this. Hope it proves helpful.

David

[David Dunlop]

The Crystal Calibrator Panel on my Main Set Receiver was very badly scratched up, including several across some of the lettering, so I decided to replace it with the panel from my spare receiver, which had only a couple of small visible paint chips and a few larger ones around the perimeter that is hidden under the upper receiver front panel. The first three photos show the original panel, the original replacement panel, and the refurbished replacement panel. It turns out that Testors 1139 Semi-Gloss Black Model Paint is a near perfect match to the black paint Canadian Marconi used on the calibrator panel here.

The Crystal Calibrator is a complete, self-contained sub assembly that is mounted to the receiver chassis at some point on the receiver assembly line, by means of four small angle brackets, two either side of the rear chassis plate of the calibrator. See the fourth photo in this post. Swapping out the calibrator panel is, fortunately, a purely mechanical task, that is easy enough to do with a little forethought.

The first step is to lay the receiver on its left side on your bench as this makes access to all the necessary hardware much easier, and if any hardware falls loose, it will not disappear into the bottom of the main chassis. Then remove the calibrator switch knob. You should then notice this switch has a small key tab just to the left of the switch shaft that sits in a small hole in the panel just above the ‘FR’ of “FREQ CHECK”. Then, carefully unscrew the large hex nut securing the switch. It should have a large, external tooth lock washer behind it. Be gentle as this has been tightened against 75 year old paint that might have been bruised and you do not want large chips to pop off if you can avoid it.

The next step is to undo the ground terminal at the lower end of the 5 Watt 8 Ohm Lamp Resistor. Shown in the first two photos of the following post. You can then remove the two slotted, pan head self-tapping screws on the underside of the calibrator panel, shown in the third and fourth pictures of the following post.

Next remove the two screws on the upper front of the calibrator panel, above the Holders, Lamp Assembly. You can now gently pull the panel assembly forwards just enough to access the centre screw terminal on the back of the Holders, Lamp Assembly with a small socket. There is a small trick to this, however. Loosening the hex nut on the centre terminal to remove the connector also loosens the Lamp Socket inside the Holder and it will start to turn with the hex nut you are trying to remove. So before you start trying to undo the hex nut, remove the red lamp cover from the front of the Holders, Lamp and place a fingertip on the bulb inside with enough pressure backwards to hold the bulb and socket still while you undo and remove the hex nut.

To reassemble, do everything in the reverse order.

David

[David Dunlop]

Here are the remaining four photographs related to the previous post.

David

[David Dunlop]

The HOLDERS, Lamp, No. 1 (ZA 4201), is a very common item found on a great variety of Second World War Era Wireless Equipment. To this point in time, the only real variation I had ever run across when dealing with them was the variety of different coloured cover caps they could be equipped with across all the equipment that uses these Holders.

While recently working on my Main Set Receiver, and with subsequent help from Bruce MacMillan and Jacques Fortin, we have realized two versions exist. The difference is quite subtle but can have a profound impact on ones wireless restoration project, if any of the relevant hardware bits go missing.

It would appear the original design of these holders, whenever that was, made use of a 6BA x ½ inch central terminal screw at the back of the Holder, fitted with a chunky looking 6BA hex nut. This hex nut requires a 3/16 inch socket to work with it. At some unknown point, for some unknown reason now, production of these Holders changed such that the central terminal screw became a 4-40 x ½ inch screw with its thinner and wider hex nut which requires a ¼-inch socket to work with it.

It seems unlikely this difference is a result of two different manufacturers running concurrently with one another, only because any available documentation we can find on these Holders is dated up to and including 1944 and it all refers solely to the 6BA version. The 4-40 screw version is likely a later replacement or upgrade. It has no real bearing on the working capability of the Holder, just one’s ability to service it.

I have 6 of these Holders (two each) fitted to my three 52-Set Receivers. Two are 6BA Pattern and the other four are 4-40 Pattern, Two of the receivers have one of each.

Thought I would put this information out there to minimize other people being surprised by this hardware variation down the road.

David

[David Dunlop]

It has been a very good weekend for getting things done on the Main Set Receiver. One huge three part bit of work and a couple of detail items accomplished.

The first small item was getting the blue paint daub reapplied to the top of the Crystal Calibrator Chassis to denote all valves therein had be properly aged in prior to installation of the calibrator. One small piece of the original paint had survived. It is nothing fancy, just a random daub (more correctly a grouping of daubs of blue paint) just smaller than a 5-Cent Piece.

I could not find a 1944 Nickel in my coin bin for the photo, so a 1945 had to step in.

Before I forget, again, the paint I found that was a close match to the original is ‘TREMCLAD GLOSS MEDIUM BLUE’. I sprayed some in an empty cat food tin and daubed it on with a cotton q-tip. It is an enamel and with take several hours to dry to the touch and about 24 hours to cure under normal household temperatures.

David

[David Dunlop]

The biggest chunk of work on the 52-Set Main Receiver this weekend involved, three separate, but interconnected tasks, with a small extra one tossed in for good measure.

The collective objective was to finish off replacing all rusted or damaged components and hardware on the lower front panel, and the items being attended to were the Voltmeter, Holders ,Lamp, Loudspeaker and lower right Mounting Bracket.

The Voltmeter needed to be replaced with the one from the spare receiver as it has a cracked Lucite face and I need to send it off to be repaired. The original three mounting screws are also badly rusted. Rusted screws and a needed cleaning were needed with the Holders, Lamp and rusted hardware again with the Loudspeaker. Both the lower mounting bracket and its two screws were rusted and to be replaced.

Accessing the hardware for the Holders, Lamp and Loudspeaker is very bad, unless the Voltmeter is removed from the panel, and that is the primary reason all three bits of work were combined. The Voltmeter on the 52-Set, however, has its own challenges. Unlike the 19-Set, the hardware for the 52-Set Voltmeter does not screw directly into the front panel assembly. It has its own independent hex nuts behind the panel to contend with. Before you start that, however, it is a good idea to remove the two meter leads from their terminals at the back of the meter, while the meter is still secure.

I found the best way of getting the meter hardware off was to jamb a fingertip against the back of the hex nut to hold it in place while you unscrew and remove the mounting screw. 6BA screws and hex nuts were very likely the original hardware. I found one of these top dead centre. The other two were 4-40 items. Once the screw was out of its hex nut, I moved the nut along the back of the panel to a point where I could capture it with a small shop magnet.

Once you have removed the three hardware sets, you can give the meter a little nudge from the rear so you can grasp the front rim and slide it out of the panel. He aware, the fit is snug and I found the years of dirt accumulation on the top of the back of the meter was sufficient to bind the meter. But you can wiggle it free.

The thought of reinstalling the meter was a daunting one until I bounced the topic off Jacques Fortin. He suggested gluing the hex nuts in place first. Brilliant ,and I modified that by using clear nail polish instead. I reinstalled the good hardware, but slightly loose initially. It is extremely important to ensure the flats of the hex nuts are lined up perpendicular to the circumference of the meter opening in the panel. Looking directly into the meter opening, the hex nuts must be completely invisible, otherwise the body of the meter will hang up on them. And if you have glued them in place…

Once I had the hardware set up correctly, I applied the nail polish to the outer edges of the hex nuts, making very sure to keep the polish away from the screw threads at all costs. Then give it a full 24 hours to cure before carefully removing the screws. Insert the meter back into the panel and replace the screws. Again, at this point do not try forcing the screws into the hex nuts, You may push the nuts off the back of the panel. Let the threads on each find each other. If you want, cafefully jamb a fingertip back onto the backs of each nut until the screw is all the way through, for a little extra insurance. Once all three screws are installed, reattached the meter leads to the rear terminals and you are good to go.

While the meter in out, I used the extra space to replace the top two Loudspeaker screws. Kept a finger on the hex nuts at all times. While removing the old screw and installing the new ones. The lower two can easily be reached from the bottom of the chassis and for this, just lay the receiver on it’s left side. Same goes for the lower right side mounting bracket hardware.

The two photos are of the new meter hardware curing in place and of the Main Set Receiver with all its new and improved bits. It has come a very long way in the past year.

David

[David Dunlop]

When I cleaned up the meter needing repairs to its Lucite face, I was surprised at how much more readable the various stamps on the back of it were, compared to the same type of DeJur Company Voltmeter I commented on back in Post #140. I was, however, expecting the same 5-digit number to show up on the bottom half of the back of the meter, but this one had ‘150 14’ on it, not ‘150 24’. No clue at all at this point of the significance of these numbers.

There is also a small error to be accounted for in that earlier Post. The yellow stencil on the top edge of the meter body is a much larger font on this meter and clearly reads ‘MI4’ The smaller font I earlier posted about looked like ‘ASA’ to me back then, but on closer examination after cleaning up this meter, I can see it also reads ‘MI4’. Again, yet another mystery.

David