Wireless Set No. 52 Canadian - Project

[David Dunlop]

The last small project directly related to the Vibratory Supply was finished this morning, which involved reinstalling the hardware set that had fallen out of the right side of Panels, Phenolic No. C1 (ZA/CAN 4229). This discovery was also covered back in Posts #756 and #766.

This Panels assembly is fitted to the back end of the tray in the Supply Unit the Vibratory Supply and its Case slide in and out on. The Panels supports the three Sockets, Metal, ¼-in OD 40 tpi thread, No. C1 (ZA/CAN 4583), which are basically a form of Banana Socket the Vibratory Supply plugs into when in place.

The front collars of these Sockets have ridges in them parallel to the longitudinal axis of the sockets and the sockets are fully threaded on the outside. On the backside of the Panels, Phenolic there is a 1/16-in free space between the Panels and a pair of hex nuts run up against each other and lacquered in place. This gap allows the Sockets to ‘float’ on the Panels, which allows the plugs on the back of the Vibratory Supply a better chance to capture the sockets. Probably a gauge was used on the assembly line t make it easy and consistent to attain this gap. The Sockets and Panels assemblies were likely assembled to the tray for the Vibratory Supply, before the tray was riveted in place at the bottom of the Supply Unit chassis. This latter point makes it trick to replace the right side screw assembly that had fallen out of the Panels.

When the wiring was disconnected from the Sockets, the lowermost lock washer was covered in rust that needed to be tidied up. Removing the wiring, with its large tags provided more access to where the hardware went, in behind the chassis side frame. The other thing that was necessary was to slide a wooden wedge between the chassis side frame and the back of the Panels to hold the Panels firmly up against the back end of the tray assembly. This allowed the screw to be reinstalled to fully pass through the Panels far enough to easily engage its lock washer and hex nut when the time came to fit them.


David

[David Dunlop]

Given the tight space behind the Supply Unit chassis and the back of the Panels assembly at the rear of the Vibratory Supply tray, I needed to be sure the hex nut and lock washer stayed put long enough for the screw to capture them.

To do this, I glued the hex nut to my 5/16” Box End Wrench with clear nail polish, and then glued the lock washer to the hex nut, being sure to keep the polish out of the hex nut threads and the washer centred over the hole in the hex nut. Once dried, it was easy to hold the two parts in place and manoeuvre the screw to engage the thread in its hex nut. As the hex nut tightened down, it popped free in the wrench and shed all the nail polish. I could then switch to the open end of the wrench on the backside and a screwdriver on the screw to carefully tighten the hardware. A final wipe of polish across the back of the hex nut and it was all done, and the wiring could be reinstalled on the Sockets.

Now that is out of the way, I need to look at how best to access the hex nut binding the Case for the Vibratory Supply and fix that problem. All that work is in the Supply Unit itself but has a major influence on the Vibratory Supply.


David

[David Dunlop]

Well this part of the project is going to be full of challenges.

I need to get the Blower Motor assembly for the Supply Unit out of the way to gain access to the hardware set causing the case for the Vibratory Supply to jamb in its tray. I studied the blower for the better part of half an hour looking for an easy way to remove it. There are none. The blower assembly and its related Covers were definitely installed on the front panel of the Supply Unit before the panel was installed on the Supply Unit chassis. Then its power feed wire was soldered in place. In situ, there is not enough room to easily get even the smallest tool onto any of the Covers hardware to remove it. You can loosen it all but end up resorting to fingers to ease the hex nuts out. A small shop magnet on a telescopic stick helps, as does a small pair of needle nose pliers. But even with all that, I still dropped one hex nut and one lock washer into the innards of the Supply Unit. Fortunately, they both dropped to the bench when the supply was carefully turned upside down and I knew what two sets of hardware the bits came from. Still interesting for what is intended to be a temporary disassembly.

Once off, the Covers was actually in better shape than the one on the Sender. The screen was popped inward (as was the one on the Sender), but no screen wires were broken and the screen pressed back flat with a little gentle thumb work. The rust accumulation on the inside of the Covers and the Blower Fan Blade is about the same as on the Sender Blower. I think dust settles inside the Covers, and static clings to the fan blades. Over time, this dirt accumulation attracts moisture and then rust settles in on the surfaces. Also, the inside surface of the Covers is primed only. There is no Gloss Navy Grey topcoat inside there at all.

The large pieces of front panel paint missing inside where the Covers sat had actually peeled off and curled up into tubes inside the Covers and the red oxide primer on them confirmed the paint was from the 1966 rebuild.

That was enough excitement for this evening. I shall study and plan for the next step tomorrow.


David

[David Dunlop]

Unlike the grub screw on the Sender Blower fan, the one on the Supply Unit fan was well and truly seized in place.

Two days of soaking in sewing machine oil, lots of hand tapping on the fan hub with a suitable sized punch and I was able to pop the grub screw free and into about a one-quarter turn mode, back and forth. Another day of soaking and I was able to slowly work the grub screw back and forth more and more this morning until it came out of the hub completely.

A soak with Deoxit this time and I was able to drift the fan back and forth on the Blower Motor shaft to within an eighth of an inch of coming off completely. I then took an old, dull half-inch wood chisel, and with the blade resting on the shaft and the flat of the blade against the fan hub, I was able to tap the chisel head with a small hammer and pop the fan off its shaft.

This should make removal of the Blower Motor assembly from the Supply Unit a lot easier.


David

[David Dunlop]

Two good evenings in a row working on the Supply Unit

Yesterday I disconnected the power lead from the Supply Unit Blower Motor (Photo 1) and undid the three mounting bracket screw assemblies that hold the motor to the front panel of the Supply Unit. Exactly the same process as for the Blower Motor on the Sender, but with more limited access to the hardware in this case.

If you are planning on doing this work at any time, I would suggest you place a small sheet of paper towel underneath the Blower Motor to catch falling hardware: hex nuts, lock washers or flat washers. When they drop, they are a lot easier to retrieve on a white paper towel than when they dive deep into the bowels of the chassis and hide among all the other shiny, metallic bits and pieces.

As hoped, once the Blower Motor was out of the way, I had a good view straight down the right side of the Net Switch, at its back corner near the large metal coil box to the round head slotted screw I needed to get a screwdriver on. Once the screw was captive, I carefully tightened the hex nut and did a test fit of the case for the Vibratory Supply. It cleared the hex nut nicely, but hit the screw head on. This was a replacement screw for some reason and it was 1/16 “ to 3/32 “ too long. About ten minutes careful work with a large flat file, with a large piece of paper towel on the tray to catch all the filings, and the screw was flush with its hex nut.

Another test file of the Case this evening and it slid easily all the way back to its spring clip. A nice way to end the week.


David

[David Dunlop]

I realized after my last post that I had neglected to give much detail on how I actually removed the Blower Motor assembly from the Supply Unit, so best sort that out now.

The three mounting studs are located top left, top right and bottom dead centre and the hex nuts require an 11/32-inch spanner or small socket. Since there is not a lot of room inside the chassis to swing a spanner effectively, my tool of choice is a ¼-drive socket drive, which I use just to crack the hex nut loose. Once loose, I resort to just the socket with my bare fingers to back the hex nut to the end of the screw. I then use my fingers alone to remove the hex nut, keeping the lock washer well out of the way. With the hex nut out of the way, I then use a small slot head screwdriver to nudge the lock washer far enough down the screw shank to be able to grab the edge of it with a small pair of needle nose pliers and remove the lock washer. There is no lock washer on the mounting screw assembly in the upper right corner of the Blower Motor assembly. Electrical grounding braids terminate here on a large Shakeproof Tag, which serves as the lock washer. With the lock washers and Tag out of the way, the next item to be removed is a flat washer. It may stick a bit to the rubber grommet style shock mount behind it. If so, a small blade screwdriver will pop it loose and the same removal process as used for the lock washer works well.

I generally leave the three long mounting machine screws in place up to this point. As the hardware is loosened, the weight of the Blower Motor holds the screws in place quite nicely. I start with the lower mounting hardware, go to the upper right set and finally the upper left. While holding the Blower Motor with one hand, I remove the three screws in the same order. To remove the assembly, I moved it straight back into the chassis and swing it to the left as the fan shaft at the front of the motor clears the front panel. This will bring the Blower parallel to the inside of the front panel, with the fan shaft facing the large opening on the right side of the Supply Unit chassis. You can then angle the Blower down slightly as you bring it out the right side to ensure the Phenolic Panel assembly on the back of the blower clears the chassis upon removal.

Sorry I missed all this originally.

David

[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

[David Dunlop]

The other little bit of work on the Supply Unit at the moment centres on the Screw-Eye located roughly top centre of the front panel, just above the lamp assembly.

This Screw-Eye was forced closed by a blow from something, to the point the connector cable from the receiver to the sender would no longer pass through it. The first two photos here show how the two working Screw-Eyes look on the Sender, and how the one for the Supply Unit currently looks.

These Screw-Eyes have a 3/8-inch ID. When I was cleaning up the two for the Sender, I took a tapered punch and slid it into the two Sender Screw-Eyes, marking how far it went with a wrap of masking tape. This gave me a reference for the damaged one from the Supply Unit. The 3rd photo here shows a block of 4 x 4 with a 3/8-inch hole drilled into it, and the punch. The right side of the masking tape is the needed reference line. The 4th photo shows how short the damaged Screw-Eye from the Supply Unit falls from the reference line, when slid down the punch, and the last photo shows how the punch was then used to drift the screw-eye open once more.


David

[David Dunlop]

I am going to use the shank of my 3/8-inch drill bit to reform the damaged Screw-Eye off the Supply Unit. The attached photo shows the start point of the basic concept. I am in no rush and the bulk of reforming the correct circumference of the screw-eye should be relatively straightforward.

Where it is going to get challenging is at the point of closure between the end of the ring, as it gets closer to the shank of the screw. The shank must maintain an orientation of being perpendicular to the circumference of the ring of the Screw-Eye. Or to put it another way, the shank of the screw must point to the centre of the eye when I am finished.

David

[Bruce MacMillan]

Originally Posted by David Dunlop

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

Another way to measure the voltage is to make a voltage divider with some resistors. Use two equal value resistors in series of high enough value that there is very little current draw, this means they don't have to be high wattage. Measure the voltage drop across each and add together. Dividing the output in two puts the voltage across each to around 1000V. If it is still too high for your meter you can use 3 resisters to get each voltage drop below 1000V.

[Chris Suslowicz]

Bear in mind that resistors have a voltage rating too, and that high value low wattage resistors may flash over rather than burn out if the voltage rating is exceeded. For high wattage resistors you can assume the voltage rating is adequate for the full power rating, so voltage = square root of (resistance value x power rating).

For your 8.2k 10W resistors that's 286 volts and with 4 in series = 1145 volts which should be fine.

Using them all in series as a test load and with a suitably high resistance multimeter (20k ohms per volt), you should have no problem measuring the output voltage on a 40 watt (approximately) load by using the meter between ground and the 'hot' end of the lowest resistor in the chain. (I'd suggest starting on the 1,000 volt range of the meter first, just in case.)

Then multiply the meter reading by 4 to get the actual (approximate because the resistor could be only within 20% of its marked value) voltage.

Alternatively, you can put the meter in series with all the resistors and measure the current through the chain - put the meter between ground and the lowest resistor and don't touch it when the power is on (if the meter is open circuit parts of it will be at full HT voltage and that is definitely lethal) - then multiply total resistance by current drawn to get the applied voltage.

Chris

[David Dunlop]

Bruce and Chris.

Thank you both for the comments. You have confirmed I am on the right track.

I have found with this project that there are not nearly enough opportunities so far to actually work with the various equations and formula used with electronics work. The gaps between usage are so great I forget a lot of the details and then spend a lot of time having to refresh my mind on how they all work. Your assistance is much appreciated.

So far, my calculations suggest I am going to be dealing with about 4+ Watts, testing the dynamotors, and the one rule I am going to be focusing real hard on when the time comes, is 'Keep my left hand on my lap at all times!' .


David

[David Dunlop]

Fun day today! Sitting inside watching the 3rd blizzard in a week roll into town.

I have been able to do some more work on restoring the Screw-Eyes, 4-40 for the top of the Supply Unit front panel. The circumference of the eye is now true, but the gap at the shank still needs to be closed up. It currently sits at about 3/32-inch wide, which is just enough for the lock washer to slide all the way around the body of the screw-eye.

The more I look at it, I am thinking that if I can close the gap up properly, the longitudinal axis of the shank should automatically end up pointing directly at the centre of the eye, so I might get a break there.

A couple of before and after photos posted today of the work so far.


David

[David Dunlop]

I was mulling over how to close up the final gap in the Screw-Eyes assembly for the Supply Unit without compromising the uniformity of the circumference of the eye and a pair of pliers on my bench caught my eye.

A lot of pliers have a built in cutter between the jaws and the pivot point of the handles. The backside of the cutters is typically cut away in a circle, the diameter of which varies to some degree. I rummaged in the tool chest and found my Dad’s old black handle pliers and this cutter hole was just the right fit to carefully close up the gap in the Screw-Eye.

This screw-eye now matches the gaps in the two on the Sender and the lock washer stays put once slipped onto the shank and the hex nut installed. Last photo today shows the Supply Unit Screw-Eyes all polished up with the pin terminal of the connector for the receiver sitting nicely inside the Screw-Eye. The free play inside the eye matches that in the two screw-eyes on the Sender.

A little more progress accomplished. I might just celebrate by shovelling the snow off the front walk from yesterday’s blizzard.


David

[David Dunlop]

I have now temporarily reinstalled the Covers for the Blower Fan and the Knobs, Metal on the front of the Supply Unit, after repainting them Gloss Navy Grey. It only took two hours to get the four lock washers and hex nuts onto the Covers and lightly secured. Definitely a job best done with the front panel of the Supply Unit off the chassis of the supply. I had to resort to using Debbie’s jewellery pliers and a toothpick to fit the washers on the screw studs, and an assortment of small 5/16-inch drive sockets to get everything back in place. Wonky fingers did not help either.

I will refit the Screw-Eye in the next day or two.

The new paint really stands out against the old, amber tinted varnish on the front panel paint, with all its stains and missing bits, but that garish contrast will tone down a lot when the front panel gets its restoration and repaint. The contrast then should be identical to what took place on the Sender front panel when that work was done. I can at least continue on with the electrical testing of the Supply Unit knowing everything is safe and where it should be for the time being.


David

[David Dunlop]

While I was mucking about with the reinstallation of the Covers assembly for the supply unit Blower Motor today, I made yet another discovery regarding production of the 52-Set.

When I shifted one of my desk lamps to get better illumination of the upper left mounting post of the Covers assembly, the lamp lit up the top of the front end of upper MG1A HP Dynamotor. I had noticed a yellow C-Broad Arrow mark there earlier when looking at the data plate for this dynamotor, but above this stamp I spotted a yellow Philco Stamp and above it a square, yellow, ‘TESTED OK” Stamp. I have run across that latter stamp on a couple of other components of the 52-Set so far, but what intrigued me here was finding further involvement by Philco with production of the 52-Set.

These dynamotors were built by Robbins & Myers, and all produced in 1945. To date, no surviving components of a 52-Set have been found with a production date of 1945. All have been dated in 1944. So the entire production run of 52-Sets, pushing somewhere close to 5,000 sets, probably ended sometime late in 1944 at Canadian Marconi Company, while the contract for upgraded dynamotors for the 52-Set took place in early 1945 at Robbins & Myers. Based on the Philco Test Stamp, is it possible Canadian Marconi was preoccupied with finishing off any wartime contracts it could while also trying to switch gears back into new military or civilian production, possibly also reducing staff, and did not have the capability of testing the replacement dynamotors, so had Philco do it for them?


David

[David Dunlop]

Well I bit the bullet and started the electrical tests of the Supply Unit today. Three of the tests came from the 1st Echelon Maintenance Schedule and confirmed both dynamotors spooled up and the fan circuit remained dormant. That latter test directs the operator to further tests if the fan had activated.

A couple of initial observations were that with both the MG1A and MG2A dynamotors running, and the Supply Unit free standing on the bench, the noise they produced was noticeably less than that created by the 19-Set dynamotor, when that supply is running outside of its case. I was quite impressed about that.

There was a bit of a ‘sandy’ sound coming from the area of the input brushes of MG1A (described as the 11Volt Brushes in the circuit diagrams), so I will check them out once the front panel comes off, because they are hiding right behind it.

I then hooked up my analogue test meter to the MG1A output feed to see just how well this dynamotor was working. At 12 Volt input and under load, the output should be 300 Volts. Under no load at 12 Volts, the regulation of MG1A should not allow it to exceed 35% additional output, or a total output of 405 Volts.

When switched on, it took the meter needle about 1 second to climb from 0 to 300 Volts and another couple of seconds to reach 380 Volts. Two more seconds and the needle stopped one width away from the 400 Volt mark and held there. I am thrilled with those results as my CPP-2 Power Supply was feeding a steady 12.73 Volts DC into the Supply Unit.

Next step will be assembling my string of resistors and seeing what the output of the MG2A dynamotor is doing. In the meantime, I cannot help wondering when the last time was that these two dynamotors were active.


David

[David Dunlop]

It has been a while since my last update, but not much has been done on the project, primarily due to the fact I have not been able to source appropriate resisters needed to determine the output from the MG2A HP Dynamotor in the Supply Unit. Either no stock exists in town for reasonably priced resistors, or they have to be ordered in at ridiculous prices per unit plus shipping. I just cannot justify the expense for a 30 second test and then never use the resistors again.

I did bounce some ideas around with a friend and came up with a simple, quick test I can do using available equipment. It will not give me specific output data, but will tell me if the HP Dynamotor is in good working order, with enough confidence I can continue. Of course, there is still a wrinkle. I will only be able to perform the test when the front panel comes off, as I need access to both Low Tension terminals tucked in behind said panel.

The plan will be to feed 120 Volts AC into the two HT terminals and read the voltage output at the two LT terminals. It should be around the 1.5 Volts AC level if the windings in the Dynamotor are all in good working order. In the meantime, I have been running the Supply Unit on the bench for about 5 minutes a go, every few days and all appears just fine so far.

On a much brighter note, about 10 days ago we bit the bullet and finally bought a brand new 24-inch iMac to replace our original 21-inch from 2006. Been busy setting it up and doing the usual data clean and transfer from the old one. I have also downloaded some design software manuals onto my iPad to read up on. I think one of them may solve all, or most of the problems I have at the moment regarding the ability to design and make water slide transfer decals necessary to restore the front panels on the Supply Unit and Coils, Aerial Tuning assemblies.

So the overall project is still headed in the right direction.


David

[Chris Suslowicz]

Originally Posted by David Dunlop

I did bounce some ideas around with a friend and came up with a simple, quick test I can do using available equipment....

The plan will be to feed 120 Volts AC into the two HT terminals and read the voltage output at the two LT terminals. It should be around the 1.5 Volts AC level if the windings in the Dynamotor are all in good working order.
David

Er... <Mode=HAL> I'm sorry Dave, I'm afraid you can't do that. </Mode>

It's a _rotary_ transformer, which is a DC motor and DC generator sharing a common field winding. It only works in one direction, and then only when it's rotating at the designed speed.

To run it in reverse you would need to separate out the field windings and feed those with 12V DC, feed the output (high voltage) armature winding with high voltage DC (high enough to overcome brush and bearing friction), and measure the voltage across the LT brushes. This is simply not going to work.

If you have had the unit running without excessive current being drawn or smoke/sparks being generated, you can assume it's OK to use - at least for short transmissions.

Best regards,
Chris.

[David Dunlop]

Thanks for the feedback, Chris. Good thing the Drawing Board for this project is huge. The Supply Unit, being the smallest item, and heaviest, is proving to be the most challenging. Very little on it still to be done, can be effectively done without major disassembly rearing its head. Something I really only want to tackle once, things being such a compact fit.

David

[David Dunlop]

When I was working on the Sender, I had taken the testing as far as I could, which was basically up to where a working Supply Unit was needed to feed the Sender for any further testing.

I have gone as far as I can now for the moment with testing the Supply Unit. I completed a set of Resistance Tests this morning. All results were on the mark but one, where I got a 74 Ohm return where there should have been 150 Ohms. I also completed all but one of the Operator’s Maintenance Tests for the Supply Unit. These could be run with the Supply Unit either in, or removed from the Carriers No. 4 and all tests gave positive results. The last test of this group is to turn on the Sender Heaters to let the Sender warm up and then flip the Send/Receive Toggle Switch to ‘SEND’. One should hear the relays in the Sender kick in to isolate the Receiver and both Dynamotors should kick in. A HT1 Voltage reading for the Sender of about 300 Volts DC should also show on the sets meter.

I have a much greater appreciation of why a pair of jumper cables for the 8-Pin Connectors between the Supply Unit and Sender are such a great idea. You can do these tests outside of the Carriers No. 4 with the internals of both the Supply Unit and Sender fully visible. Way too nerve wracking when everything is out of sight.

So back the Supply Unit went into the Carriers No. 4 and everything got reconnected. I turned on the CPP-2 and gave it a 5 minute warmup, and then turned the set on. As soon as the Receiver came on line with the WWV Signal at 10.0 MC, I turned on the Sender Heaters and let the set warm up another 5 minutes. With everything on the Sender roughly tuned into 10.0 MC as well, I then turned on the NET circuit in the Sender. The Dynamotors kicked in nice and quiet, but the HT1 reading for the Sender was only 110 Volts DC, not anywhere near the expected 300 Volt range.

Last critical test was to turn off the NET Switch and flip the last switch on the Supply Unit from RECEIVE to SEND. The isolation relays kicked in perfectly and both Dynamotors wound up, but they were under a very heavy load and very growly. The Sender HT1 Voltage was still no higher than the 110 Volts DC from the previous test so I switched back to RECEIVE right away. So something in the Sender does not want to play well with the other components. Good to know.

Next tests will be to go back to the NET Test and take meter readings for all the Sender valves to see how they compare to the specifications in the manual.


David

[David Dunlop]

Just a quick look at the set now with the semi-restored Supply Unit temporarily reinstalled in the Carriers No. 4.

Also a close-up of the Screw-Eyes restored and functioning as originally intended at the top of the Supply Unit. With the Connector Cable now able to run through the Screw-Eyes instead of over/around it, it has about one-half inch more free play in it and now looks just as relaxed in place as these connectors do in the surviving wartime photographs.


David

[David Dunlop]

As I have mentioned before, working with the surviving documentation for the Wireless Set No. 52 is a real challenge for a whole host of reasons, but it is what it is. You just have to read through every document you have, frequently several times, to locate all the information available for any given topic, and then make the best sense of it you can.

A good example recently surfaced regarding the Brushes in the two Dynamotors. Most of the available information regarding the inspection and maintenance of these items states the eight brushes should be inspected monthly for damage and wear. They should be carefully removed from their holders, checked and put back exactly as they came out. New ones must be worked in with an hours run time under no load. None of the information I had found to date advised how to access all the Brush Holders in situ, and the removal of the actual Dynamotors from the Supply Unit for servicing covered only the upper one (MG1A).

Not sure how I missed it up until now, but I was looking through the Working Instructions last evening and discovered a little table tucked away near the back of it explaining how to inspect each of the eight brushes when the Supply Unit is out of the Carriers No. 4, which was a very nice find. It also mentioned it is not necessary to completely remove the brushes from their holders to inspect them.

I posted the page here for future reference.


David

[David Dunlop]

Slow and steady still with this project, focusing primarily on ensuring the Supply Unit is in good order before going back to the Sender.

I have now confirmed the oddball reading of just over 70 Ohms I got on one of the Supply Unit Resistance tests relates to a pair of 300 Ohm 1/2-Watt resistors set up in two parallel feeds in the Vibrator circuit for the Receiver Supply. This parallel arrangement of the two 300 Ohm resistors should produce a resistance value of exactly one half the rated value of either resistor, or 150 Ohms. So one, or both, of those two resistors has dropped significantly off specifications. Confirming test yet to be done.

I spent a chunk of yesterday afternoon searching the web for a supply of 300 Ohm, 1/2-Watt Carbon Composite resistors, which proved a bit of a challenge. Current standards now bracket that Ohms value by about 20 Ohms either side. I did, however, eventually find a supplier with 300 Ohm 1-Watt carbon composites which will work nicely, so will be ordering 10 for the project. That will give me a chance to match a pair for this fix and leave me spares for the rest of the project, if needed. The two in the Supply Unit are R13D and E, so at least three others are in the 52-Set in other locations.

When I had reinstalled the Supply Unit in the Carriers No. 4 to allow for the Isolation Relay to be tested in the Sender, I had the meter set up to monitor the Sender data. Last evening, I fired up the Receiver to see how the signal from WWV at 10.0 MC was behaving, so I had switched the meter back to monitor the Receiver. I was very surprised, and pleased, to see the LT was reading a rock steady 11.25 Volts DC and the HT a rock steady 155 Volts DC. Checked again this morning and same results. They are no longer wandering all over the dial, as low as 10 Volts LT and 120 Volts HT. What I find odd is I have yet to do any electronic adjustments or repairs to the Supply Unit that may have caused this to happen. I still intend to more closely examine the Connector assembly between all five 8-Pin Connectors across the set, but another related possibility is oxide buildup on all those contacts, so I shall add cleaning all the related sockets and plugs with Deoxit just to be sure.

I have also noted that when the time comes for hot testing the Sender, it needs to be done at High Power. I am glad I picked up the extra CPP-2 Power Supply from Brian Asbury last year. It is soon to come in real handy.

David