Wireless Set No. 52 Canadian - Project

[David Dunlop]

Although the Blower Motor assemblies for the Sender and Supply Units of the Wireless Set No. 52 are fundamentally identical, they cannot be directly swapped from one component to the other because their respective tag panels fitted to the backs of the motor housing are different.

The blower assembly in the Sender is centred much lower down on the front panel than the blower assembly in the Supply Unit. As a result, there is less clearance above the blower assembly in the Supply Unit to mount any other components.

Each Blower Motor Assembly comes fitted with its own Hash Suppression components for when the fan is operating. These consist of a small RF Choke Coil and a Capacitor. In the Sender configuration, PANELS, Phenolic, 3-Tag, 2-3/8” x 2-1/4” x 1/16” (ZA/CAN 4591) is employed. It is tall enough the large capacitor can be mounted across the front of the Panels above the Blower Motor housing and the smaller RF Choke Coil directly behind it.

With less space in the Sender to work with, Canadian Marconi placed both hash suppression components across the back of the Panels; the capacitor directly above the coil. The circuit references in the Supply Unit for these two parts are C3AJ and L30A and the Panels, Phenolic, 3-Tag, 2-3/8” x 1-3/4” x 1/16” is ZA/CAN 4521.

When I was studying the Blower Motor assembly in the Supply Unit prior to removing it, I had noticed the upper right corner of its Panels, Phenolic, 3-Tag was sitting quite a bit higher than on the left. When I was cleaning the dirt off the blower motor yesterday, I found a large black dash on the top of the mounting strap and this ‘dash’ was located to the right of the large central wiring grommet in the top of the blower motor housing (See photo in Post #805). Looking at this more closely, it appeared that if I loosened the mounting strap enough to turn the dash to centre by the grommet, that might just level out the top edge of the Panels, Phenolic, 3-Tag. I tried it and it worked. So the Blower Motor assembly is now ready to temporarily be reinstalled in the Supply Unit.


David

[David Dunlop]

I was able to finish cleaning the fan blade this morning and it now slides on and off the shaft of the Blower Motor quite nicely.

The two blades that had assumed the lower position while the 52-Set sat idle for years had quite a bit of rust accumulation that showed up as a darker area of small pitting once the blades were cleaned and polished. Whatever company made these fan blades did a very nice job of the nickel plating. It is very heavy duty and has held up well over the years, all things considered.


David

[David Dunlop]

The Blower Assembly and Fan are now back in the Supply Unit for the time being. I just have to resolder the power feed line to the blower, which I will probably do tomorrow.

The Case for the Vibratory Supply is back where it belongs as well.

As I suspected, some fine-tuning of the front panel of the Vibratory Supply was needed to get it to align with the main Supply Unit front panel. I did that by putting the Supply Unit on its back on two pieces of 2 x 4 wood to protect the two 8-Pin Connectors for the Supply Unit and inserting the Vibratory Supply. By backing off the two SEMS Mounting Screws for the front panel of the Vibratory Supply, and the Knobs, Metal, enough wiggle was created in the front panel of the Vibratory Supply I could get it to drop into place correctly and lock the two Shakeproof No. 18 Fasteners and retighten the three pieces of hardware.

Now I can at least see where the restoration of the Supply Unit is headed.


David

[David Dunlop]

Last evening, I was able to resolder the power feed to the Blower Motor in the Supply Unit, so electrically, the Supply Unit is ready for testing the Dynamotors with no loose wires flopping around inside the chassis.

I also did some thinking about the next steps for the Supply Unit.

The original idea was to leave repainting the Covers for the Blower, and the final caste zinc Knobs, Metal until I was able to completely restore the main Supply Unit front panel to original look, and then do the final reassembly. I now want to get these last two pieces on the Supply Unit painted Gloss Navy Grey as soon as possible, hopefully, this coming weekend. The motivation for this comes from the fact that while recently painting the front panel of the Vibratory Supply, my can of high gloss enamel was not sounding right and the nozzle briefly clogged. I am guessing there is about one quarter can left and the can is coming up to two years old. If this can of paint behaves long enough, I can get all the required Gloss navy Grey parts painted from the same can/paint batch, I am guaranteed a match across the entire 52-Set. My concern is further heightened at the moment by the fact that none of the suppliers of this paint in Manitoba have this colour in stock. Four exist in Saskatchewan but getting them here is yet another unknown, and they would most definitely be from a different paint batch. So fingers crossed this weekend coming.

In the meantime, both the Covers, and the Knob have been stripped of old paint, cleaned and primed ready to go. As far as the Covers goes, it is being done like the one earlier on the Sender. The factory original paintwork on these items was to leave the inside surfaces raw plated metal, with just the exterior primed and painted Gloss Navy Grey. The inside surfaces cover in rust quite easily over time so both Covers got a coat of grey primer inside and out and only the outside will get the final gloss enamel colour. Once back on the front panels, the interior of the Covers that can been seen through the wire screen, looks close enough to plated steel to not be noticeable and at least that metal is now protected a little better than originally.


David

[David Dunlop]

Another good weekend for slowly moving forward with this project.

I started early Saturday morning with a quick trip to the local Canadian Tire Store to obtain some information. As I suspected, they do not do ‘inter-store transfers of products’ due to the fact all stores are privately owned franchises. They also do not ship out of province from any store apparently, to keep the paperwork simple. So that ruled out any easy way of getting more ‘Gloss Navy Grey’ spray paint, if I needed to do so.

Back home, I took a deep breath and set up to get the Covers and Knobs, Metal for the Supply Unit finish coat painted. Happily, everything went smoothly and they will be ready to temporarily reinstall on the Supply Unit at the end of the month.

In the meantime, I have to dive back into Ohm’s Law and see what calculations I can come up with to get the testing completed on the power output of the Sender section of the Supply Unit.


David

[David Dunlop]

While all things ‘Gloss Navy Grey’ were swimming through my head the other day, I made an interesting discovery with the 52-Set that I had completely missed up until now. The one other part of the set which was painted Gloss Navy Grey and which would never have received a coat of varnish, is the SCREENS, Metal, Perforated that protects the front of the loudspeaker in the Receiver.

I only noticed this while looking at my Remote Receiver, which is all original, except for the new Tuning Dial Plate that was installed at some point in its service life, and the addition of the white decal under the Meter stating this replacement dial is ‘None Luminous’. While looking at the decal, I suddenly noticed the Screens assembly was the same grey as the Knobs, Metal on the receiver. A quick look at the Main Set Receiver, which had some Shop work done on it at one point, and I noticed its Screens had received a coat of varnish and was showing the typical patina that developed over time.


David

[David Dunlop]

Work is still plodding along with the Supply Unit in a number of areas. The Covers and Knobs, Metal are curing quietly away until the end of the month, when they can be reinstalled and I have been working on two other objectives in the interim.

The first item I have been struggling with is the output capability of the two Rotary Transformers (Dynamotors), MG1A HP and MG2A HP in the Supply. The MG1A HP unit I am comfortable working with as its output is well within the testing limit of all my available test equipment, which has an effective DC Voltage limit of 1,000 volts. The MG2A HP unit, however, is a different animal entirely, for which I had to dust off my math skills to really understand it. So if you are ready for some really boring trivia, here goes.

The information Robbins & Myers provided on their data plates for the two rotary transformers is as follows:

MG1A HP:

Input: 11 Volts @ 8.5 Amps
Output: 285 Volts @ .15 Amps

MG2A HP:

Input: 11 Volts @ 25 Amps
Output: 1,300 Volts @ .12 Amps

These values would have been obtained under a full load test and I am assuming that since these two rotary transformers were the upgraded ones produced in 1945, the load would have been the Sender Unit of a complete 52-Set very likely provided to Robbins & Myers by Canadian Marconi for the purposes of developing the new dynamotors. What really caught my eye was the input voltage used by Robbins & Myers was only 11 Volts DC. Then I remembered a cautionary note in the 52-Set Operator’s Manual advising that once the sets wireless batteries reached 10.5 Volts DC, they must be replaced with fresh batteries and recharged immediately, because the performance of the 52-Set will be compromised otherwise. So Robbins & Myers probably set 11 Volts DC as the lowest effective voltage to test the dynamotor performance against.

While trying to glean as much useful information as possible out of the Overhaul Manual for the 52-Set, I found a reference to the output voltages for the two rotary transformers from Canadian Marconi’s testing.

“The output voltages of the supply unit shall be within the following limits with an input voltage of 12 Volts measured at the terminals of the supply unit end with full load on the output circuit:

MG1A supply: 300 Volts +/- 10% at 175 mA.

MG2A supply: 1,430 Volts +/- 10% at 120 mA.

End Quote.

Again, from the Operator’s Manual, the optimum voltage from the wireless batteries is noted at 12.5 Volts DC, and that value pops up from time to time in the manual, but 12 Volts DC is the normally expected operating voltage for the 52-Set. So Canadian Marconi used 12 Volts DC for their testing.

When you look at the DC Voltage increase between the two tests, you get an upgrade of 7.09%. The increase in output for the MG1A dynamotor comes out at 7.5% and the similar calculation of the MG2A output gives us a 10% increase. So a 1 Volt DC input increase produces a close similar percentage increase on output.

Where things got really interesting was a later comment on the Overhaul Manual from Canadian Marconi:

“The voltage regulation of the supply unit from full load to no load on the output circuits shall not be more than the following:

MG1A Dynamotor 35% at 175 mA.

MG2A Dynamotor 40% at 120 mA.

End Quote.

So if the Supply Unit of the 52-Set is in a stand-alone mode on the bench being tested, as mine will be at the moment, the “no load” output of the two dynamotors will be in the area of:

MG1A 405 Volts DC

MG2A 2,002 Volts DC



So the MG1A HP unit is well within the safe test range of my available multimeters, but MG2A is alarmingly over this limit. On the bright side, back when I was restoring the ZE-11 Remote Supply for the Remote Receiver, I had to but some 10-Watt Resistors to fabricate the correct test load. I think I have 4 x 8.2K Ohm and a pair of 3.3K Ohm ones tucked away and will have to sort out if that will be enough to get a testable output voltage under the 1,000 Volts DC mark.

Never a dull moment with this project.


David