Wireless Set No. 52 Canadian - Project

[David Dunlop]

One other small note.

We are getting used to being able to reach the full Internet once again with our new 24-inch iMac. We still have to get an external storage drive to transfer all the photos and documents from the old iMac onto, which will probably take a while behind the scenes. We were reasonably diligent enough to ID nearly all of our photos and set up a filing system, but failed to keep transferring new photos to the files consistently. It will be a time consuming pain to get it all sorted, but we will, this time. It makes life so much easier when done and adhered to.

I have also now been looking at Vector Graphics software as a potential solution for the water transfer decal project down the road. What appeals to me about it at this point is that it can remove the print dots and pixels from digitized printed images and thereby allow the images to be enlarged without the image breaking down. That would be a huge help as few, if any, Supply Units or Coils, Aerial Tuning seem to have survived with factory original decals still in place, so the panel photos from the Operators Manual are the only viable option.

David

[David Dunlop]

With the realization a couple of weeks ago that the next major step in restoring the Sender is going to be completion of the remaining tests, it also dawned on me a number of those tests require the set to be actively running in HIGH Power Mode. Initially I was thinking it was great I had purchased a second CPP-2 Power Supply from Brian Asbury a couple of years ago, as that gave me the ability to have enough amperage with the two running in parallel mode, to avoid any problems operating the 52-Set. Then last week, I realized I did not have a second set of output cables to hook up the second CPP-2 to my 12-Volt Distribution System. So I quickly emailed Brian to see if he still had any of these in stock. They were initially C42 Set items. He advised me he did not, but that he did have a Chorehorse connector that might work for me, and sent me a photo of it.

This cable arrived in the mail this morning. It is NOS, still with the factory original cotton twine holding it all together. See the first photo. When I finally saw this cable up close, it jogged my memory and off I went to search the Illustrated Parts List for the Wireless Set No. 52. What I found is the illustration in the second photo: Connectors, Twin, 5-ft, No. C1 ZA/CAN 4732.

Brian’s reference for this cable is: Connector, Twin, 6-ft ¾-inch, No. C1 ZA/CAN 9682.

I have found it is always a bit of a challenge trying to figure out how the measurements of many wireless cables are derived. When I put a sewing tape to this one, the loomed centre section is 55 inches long. From the end of the loom to the two lugs is another 5 inches. From the loom to the two clips is a further 15 inches. So both the 52-Set references and Brian’s could apply to this connector.

The ZA/CAN 4732 reference for the battery cable used with the ZE-12 Remote Supply in 1944 probably was used with the ZE-11 Remote Supply for the Wireless Set No. 9 Mk I that predates the 52-Set. My three wartime Chorehorse manuals and all my 19-Set and 52-Set Ground Installation manuals mention CONNECTORS, Twin, No. 53 ZA 2794 as the sole item used to hook up the 6 –Volt DC Chorehorse of the day to the Switchboards. This cable is listed as a 30-foot rubber covered item and its ZA-Number is very low.
So the mystery is whether or not ZA/CAN 4732 and ZA/CAN 9682 are one and the same cable? The latter ZA-Number suggests a post-war item; perhaps from the time 24-Volt Wireless Equipment was becoming common. Chorehorses by that time were largely 12-Volt Units. So maybe the wartime 52-Set cable was reintroduced with a new ZA-Number, based on the change in voltages in Chorehorses from 6 to 12 Volts.

In any event, I am thrilled to have this cable now, as it will truly be multifunctional with this project.


David

[David Dunlop]

While taking another look at the new Connector Cable this morning, I noticed a rubber grommet at the end of the loom on the lug side of the cable. This grommet does not exist on the wartime Connectors, Twin, 5-ft, No. C1 used with the Remote Supply. The battery terminals on this supply are located on the lower chassis, outside of the area enclosed by the Cover Assembly of the supply.

So maybe this later version of the Connector Cable had to pass through a cover/door/panel on whatever piece of equipment it was intended for, in order to reach the terminals it had to be hooked upon. Maybe it was the addition of this rubber grommet that prompted issuing a new ZA Number?


David

[Chris Suslowicz]

As I understand it, the length given is that of the wire/cable only - and the length you cut off the reel to make up the assembly.

The WS19 connectors started out as an immense range of 12-12 and 6-6 leads, with the connector faces in the correct orientation (crimped and soldered in place) for the application.

The next version (with bakelite connector inserts and repositionable connector shells (remove spring clip and rear cover, rotate front of connector to desired position, replace rear cover (which locked it in position) and spring clip) made things a lot simpler, reducing the range needing to be carried) was repairable, could be modified by the installer, and reduced the range to (approx.) 16 distinct variants (Connector, 12pt, No.50A - 50P)

Post-WW2 they were referred to by the cable length, so you didn't need a manual to find out which suffix letter was required for a particular job.

This also works for wire and rod aerials: the Aerial 100-ft No.5 is made from 100 feet of Wire, Electric, R3, and that includes the loops and straps around the insulators, so the aerial never has a physical length of 100-ft (unless someone screwed up while making it up - I have a Canadian 4-section aerial that is unusable because the first section is 10-ft too long!)

Sectional rod aerials are the same: the 14-ft folding rod for WS62 is made from 7 sections each 24-in long, and there is no allowance made for the 1-in or so lost in the joints.

Best regards,
Chris.

[David Dunlop]

Thanks for the input on wire lengths, Chis. Much appreciated.

My apologies if rumours of the death of either myself, or this project, had begun to circulate. Neither is true.

I have been sidetracked during the three sets of resistance tests I needed to complete on the 52-Set Sender. The main cause was some very odd readings I was getting. The initial assumption was a serious fault, or faults, lurking somewhere in the Sender, but as I pondered all the data; a more likely suspect for the high readings began to be my Digital Multimeter. It has performed very well whenever I needed to test a more modern, solid-state piece of electronics and never gave its reliability much thought. I began to have second thoughts when so many Sender tests started showing up where the DMM sampling rate simply would not stabilize, and would start a massive sweeping action, either in Full Auto Resistance Mode, or a narrower manual resistance range. In Auto, it invariably ended up reading at Infinity and stop working.

15 or so odd results showed up in the final data collection and I was suspicious enough to pull out my RCA VoltOhmyst VTVM (actually the recommended VTVM in the Canadian Army Test Instructions for the Wireless Set No. 19 and the 52-Set) and randomly sampled three of the odd tests. All three came back higher than I would have liked, but not even close to the ‘Infinity’ values the DMM was giving me.

So I started redoing the testing with the RCA Analog Meter for all the really odd values and from time to time rechecked a few of the tests that came back OK on the DMM. All was going well for a while and then the good test results started going off. A quick check of a couple of known resistance standards showed those results were now out and panic set in. After about a week, it dawned on me I had been watching the RCA Analog Meter warm up and was checking the Zero status of the needle in voltage mode while the meter warmed up, but had forgotten to also Zero the needle for Ohms. So I tried that and could not get it to Zero to save my Soul. I had put a brand new pair of D-Cells in the VTVM in January, so they were not on my radar, but should have been. When I finally realized they were worth a look, one tested 1.34 Volts and the other came in at 0.32 Volts. Popped a brand new set in and problem solved.

In the meantime, checking my two digital multimeters showed both were quite accurate and the RCA gave me results that were so close to correct resistance values I was a happy camper. However, my only backup analog multimeter, a cheap modern one about 15 years old, was consistently 25% off values for resistance, It’s manual claimed +/= 5% when new. So I was short a reliable analog backup.

I have now found a very nice, very accurate Simpson Model 303 VTVM, and being a give away, I am a happy camper and can now get these tests finished on the Sender.

David

[Bob Carriere]

Batteries do fail....even new from the package.

Digital is fine to a point...... when it goes South there is no fixing....

and how quick we get used to instant results........ old radios were famous for taking it time to warm up....anything with tubes need patience.....which years ago did not seem to bother us...... You are one of the few left who exudes of patience, persistence and problem solving skills with the old electronic radios....

My old tube tester instructs in bold character to allow the instrument to reach room temperature than 10 minutes for proper warm up....... and then to proceed with an item of known value before testing components.

Always enjoy reading your trials and tribulations........

Bob C

[David Dunlop]

Thanks, Bob.

This project certainly generates them.


David

[David Dunlop]

When I recently got the Simpson VTVM, the other half of the equipment ‘give away’ it came with was an older bench Frequency Counter rated to 80 MHz. I haven’t a clue if it will ever be useful in working on either the 19-Sets, or the 52-Set Project, but what the heck...it was free.

It is all solid state, probably late 60’s or 70’s in design, utilizing a probe to connect to the equipment being tested. Currently hunting for documentation to figure out how to use it. From the little reading I have done on these things, direct hookup between the counter and the item being checked would seem to be an advantage because of the ever growing amount of RF pollution these days.

Last weekends rain/snowstorm here, which finally said goodbye last night with a cm dusting of snow, halted 52-Set work. Water got into our basement with enough enthusiasm to get ahead of the sump pump. We had a 2-inch deep 9-foot diameter pool of water that just wicked onto two area rugs and a couple of floor mats before the pump evened the odds. 20 minutes of stability and the pump finally got ahead of the incoming water. Everything is about 90% dry again and back to normal, but we certainly didn’t need the excitement.

David

[James D Teel II]

Our house flooded three times while I was growing up in SW Oklahoma. I can empathize with what you're dealing. I'm glad to see you back on and I pray the damage wasn't too severe.

By the way, I appreciate all the help you've given me with my radio. Check your email for the results.

[David Dunlop]

I am happy to help whenever I can, James.

I was able to get the first set of Sender Resistance Tests reviewed today with my now nicely calibrated RCA VoltOhmyst VTVM, after letting it warm up and stabilize for half an hour.

On the first go back on 10 April 2022, 18 of the 72 tests in this set came back noticeably off specifications and/or ‘odd’. Of those 18 reviewed today, five now came back on specification and the others were noticeably lower in value, or unchanged. So roughly 30% of those 18 readings are now resolved and the rest will need to be investigated.

The Socket for Valve V1J (an ARP-3) has half of its terminals hidden behind the Microphone Transformer T2A, which forms part of the V1J Grid Circuit. For the 10 April 2022 testing, I had chosen to test the V1J Socket terminals from the top, and the probe pins felt a bit too sloppy in the holes, so this time, I decided to remove the T2A Transformer from the lower rear chassis wall of the Sender. This is easily done, as it turns out, by simply removing the two sets of hex nuts and lock washers, as shown in the attached photos. I just let it hang carefully on its leads until the tests were completed from the bottom side of the V1J Socket and then reattached the T2A Transformer to the chassis.

Now onto rechecking the suspicious results for the second test.


David

[David Dunlop]

It was a stressful, but productive evening yesterday. I ended up spending it with my ears tuned to the sump pump in the furnace room, listening to hear if it would kick in, while my eyes were on my VTVM, getting the testing completed for the second Sender Resistance Tests.

I should take the time here to clarify a few points. All three resistance tests require the valves to be removed from the Sender chassis. The first test was a basic pin by pin check from each valve socket to ground, with, from time to time, the Mode of Operation Switch and the Power Switch in specific positions. This second set of resistance tests is taken from each of the terminals on the two 8-pin Connectors on the upper rear of the Sender, and the 7 terminals on T3A, the Modulation Transformer for the V5D Plate. Again, all readings are to ground and from time to time, the Mode of Operation Switch, Power Switch (and this time) Sender Meter Switch must be in specific positions. A total of 52 tests are involved in this set.

On the first work through, I found 21 results that were suspicious, so last evening, I focused solely on redoing all of these with the VTVM and randomly spot checking a few of the others to see if they were reliable. When all was said and done, two of the 21 tests reexamined now produced good, normal results and are now off the ‘Red Flag List’. For the remainder, all of the ‘Infinity’ readings disappeared and I got good solid resistance values back for my efforts. These are all higher than they should be, and a few are alarmingly so, but it is all data I can work with now.

It is still too early to know exactly what is going on in this Sender, but one interesting observation so far is that when the Mode of Operation Switch is in RT Mode, this seems to produce more than its share of very high readings, when compared to CW, M.C.W. and BREAK IN Modes.

In the meantime, I will try and get the last Sender resistance Test redone today.


David

[David Dunlop]

I finished rechecking the third and final Sender Resistance test this morning. All is now quiet on the Low Pressure Front.

This set of tests involves testing resistance from selected pins on the seven Sender valve sockets to just three terminals on either of the two 8-pin connectors on the back of the Sender. Some of these tests might require specific settings for the Band Selector Switch, Mode of Operation Switch or Power Switch.

22 tests make up this set and in the initial work through, I had 7 suspect results. Of those, three now came out spot on and the remaining four read excessively high, but not as bad as the first round. Interestingly, these four readings all come from the V1J socket for the Voltage Amplifier.

So now that I have believable data, the next step is to look at the actual circuits on the schematics to see what components relate to each test in the three sets of results, and start looking at those parts on an individual basis.


David

[David Dunlop]

I had my fingers crossed there was logic behind the layout of the three sets of resistance tests (there are no guarantees with electronics design) and I was happy to discover the testing sequences in each test indeed follow the Sender Block Diagram, starting at the front end with the Master Oscillator Tuning Circuit built around V5A, a 6V6G. They then added in V6A (the VR 150 Voltage Regulator) following into the Amplifiers V5B and V5C and arriving at V7A (the impressive 813 Power Amplifier). Testing then moved to the Audio Input Circuit V1J (ARP-3) and V5D, which ultimately end up at V7A as well.

Starting with the first test set, the first thing I noticed was I had good results through the first four blocks of the Sender (V5A, V6A, V5B and V5C) with the exception of Pin 1 on V5A, V5B and V5C.

A quick look at results on the third test set showed good results across all these valves as well. The problem showing up with the results on Pin 1 was that each test to ground should have produced a reading of 1 meg worth of Ohms. My readings were 1.50 meg taken from the top of the sockets; a little too high for my liking. From the bottom side of the chassis, access to the V5A socket is completely blocked and parts of the other three are tricky to get at as well. The real annoyance, however, was that Pin 1 on all of these valves is an open pin, never used by the valves and the designers take advantage of this feature to use the Pin 1 terminal on the socket as a connection tag to solder leads and wires from other components to, in order to complete other, often unrelated circuits. The issue with this is that when you look at the circuit schematics for any one of these valves, connections to Pin 1 do not show up. They are blank. The only way to find out what is connected to them is to actually look very carefully at the actual terminals on the sockets and hope the connections can be easily traced to identifiable components.

So before being able to dig any deeper into the resistance test results, I needed to get a better look at what was going on underneath the V5A socket. The attached photo shows what this section of the chassis looks like from the bottom, covered with a heavy metal plate with the Modification Card Holder mounted to it.

David

[David Dunlop]

I tend to be very careful when taking on something new, that I know nothing about and gaining access to the metal box hiding this circuit is a prime example of that action. I had no idea at all what was inside, or where and how it was mounted. I could see an access hole in the lower rear chassis wall for purposes of tuning the coil, the V5A Holder (socket) on top of the lower chassis and that was about it There also had to be a switch lurking inside somewhere for purposes of selecting Crystals.

The first discovery was this piece of metal did not exist in the Illustrated Parts List at all, first or second Issue. It was not a cover, a plate or a shield. Not an encouraging start. I then thought about the existence of the Modification Card Holder fitted to the bottom and wondered if the installation instruction for the holder might shed some light on things. It did. It was called a ‘Plate’, four screws held it in place (2 top and bottom in the photo in the previous Post), and the Plate was to be removed carefully.

After looking closely at how the Plate was installed in the Sender chassis, I could see the outside end was slipped in behind the lower left rear side of the Sender chassis rail, in behind the heavy reinforced rail the Sender slides in and out of the Carriers No. 4 on. The inside end of the Plate just slipped in beside an adjoining chassis compartment wall. So, with the Sender resting on its right side, putting the heavy rail at the top, I removed the four retaining screws and lock washers. The plate was a snug fit. I had to very carefully insert a slot head screw driver blade just into the open slot either side of the Plate at each lower side and ease the Plate out enough to be able to grab the lower edge with my fingers and pull it free, but not out. While holding it in place, I then slid the screwdriver blade carefully up the slot to the top of the Plate to keep it flush with the chassis rail. If this end of the Plate slipped inwards, it hung up on something unknown. Once you can clear the inside end of the Plate from the partition wall it attaches to, you can move the lip of the Plate inwards enough to allow the upper end tucked behind the chassis rail to drop free, and remove the Plate.

The four photos here illustrate the location of the four screws the Plate is mounted to the Sender Chassis with, what the bottom of the Plate looks like once removed and what the inner (top) of the Plate looks like, full of dirt and dust bunnies.

The real surprise in this exercise was the discovery of the hole, roughly centered in the Plate, which is effectively blocked by the Modification Card Holder. My initial though was it being another access hole for tuning something. NOPE! Turns out it is a ‘finger hole’ thoughtfully designed into this Plate by Canadian Marconi to make removing and installing this Plate an easy task to accomplish. My guess is that any surviving Senders in the UK will still have an easy time working with this Plate. Canadian owners, not so much.

David

[David Dunlop]

Finally, my first look inside this section of the Sender chassis. What struck me was how clean everything was, with little or no dirt and most important, no sign if heat discolouration or burnt smells lingering about.

The most notable thing was the pristine looking L31A COILS, RF sitting front and centre, complete with its CMC Part Number stamped on the side of it – CMC 119-209. I am not sure what prompted me to do it, but I decided to run that number against the Parts List at the back of the Operators Manual. Did that ever turn up the excitement!

According to said Parts List, L31A had Part Number CMC 119-107. The number stamped on the assembly in my Sender was nowhere to be found. So next stop was the 1945 Illustrated Parts List. It showed L31A as being, COILS, RF, 1.75-4-mc, MO, No. C1. It had a 1-1/32 inch diameter with two riveted 6-32 mounting screws at one end and no sign of a central, adjustable core. The ZA-Number reference given was ZA/CAN 4355.

A pail of tea later, I decided to check the 1948 Issue of the Illustrated Parts List for a possible explanation. Bingo! The same reference for ZA/CAN 4355 was found, but this time, directly below it was a second item, ZA/CAN 4221. It was a stink smaller diameter and was fitted to its mounting Bracket, that also held the central, adjustable iron dust core. So this complete assembly bears the CMC 119-209 Part Number.

My thought is the original design, in theory, allowed for replacement of either the coil, or the core, but the amount of work required to do either, was more than making the Coil and Bracket a single item replacement. Interestingly, the Bracket itself does not show up at all in either the 1945 or 1948 Illustrated Parts Lists. Having confirmed at this point that all the components in the Master Oscillator Tuning Circuit were replaced during the Senders last overhaul when in service, I then traced the connections to Pin 1 on the V5A Holder (socket) and found nothing worth a red flag. To be on the safe side, I retested the resistance of this Pin circuit to ground after getting a good clean contact point on the pin and now found the reading to be a steady 1.25 meg. I liked that reading and took the time to recheck Pin 1 on V5B and V5C in the same way. They both now showed 1.25 meg as well. So I was glad in the end to have opened up the shielding plate for this circuit and had a closer look.

The surprises were not quite over, however.

David

[David Dunlop]

While rechecking the Pin 1 terminal on the underside of the V5A Socket, I had noticed the two rivets securing the retaining ring on the socket to the Sender chassis floor. There was something odd about that, so I decided to look up what the Illustrated Parts List had to say. It would be an easy item to find because the Holders (sockets) for the 813 and this particular 6V6G are the only Holders in the entire 52-Set that are made of porcelain (Steatite).

As expected, it was easily found but the one in my Sender was now clearly confirmed to be a replacement item as well during the 1966 Overhaul. The attached illustration from the 1948 Issue of the Parts List shows this Holder as being of the Ring Retained style, not the riveted retaining plate as per mine. So perhaps the originals were discontinued for some reason, or got too expensive by 1966.

The last photo in this Post is of the Plate after all the dirt and dust bunnies were cleaned off the inside face.

To reinstall this Plate, at least on a Canadian Sender with the Modification Card Holder fitted, the best way is to let gravity help you.

Turn the Sender onto its left side so the heavy side rail of the chassis is on your bench. Slip the end of the Plate with the two tabs carefully down behind the rail and tip the other end in towards the bottom of the chassis. Then press down gently on the long tab at this end until it slips past the partition it fastens to and push it home until you can see the screw holes in the partition holes. Use a small nail, or similar item to centre the two screw holes and install the two screws half way home. Flip the Sender to its right side to put the two chassis rail holed to the top, do the same centering trick and install these two screws carefully home. Make certain, however, that the left hand screw in Photo 1 of Post #854, just clears the chassis rail lip it near. if not, it will hang up on the lip and dig into your bench top when you least expect it. don't ask how I know. You can then tighten the other two all the way.

If you are lucky enough to have a UK Service 52-Set Sender, you will have much better control of the Plate with a finger in the hole intended for this purpose.

Next step will be a close look at what is going on with V7A, the 813, where some seriously high resistance results were showing up.

David

[David Dunlop]

I have been looking at the test results for Valve V7A (the 813) this morning. It is quite a comprehensive set of tests in its own right for this valve. Everything gets checked twice, in each of the Power Settings, LOW, MEDIUM and HIGH and the Mode of Operation Switch set to RT. Then you repeat the tests with the Mode of Operation Switch at any of its other settings, M.C.W., CW or BREAK IN.

What I finally noticed was that the vast majority of the extremely excessive readings I got took place in the RT Mode. By excessive, I mean results that should have been 10,000 Ohms, or between 1 and 2 Megs, were coming back 25, 200, 500 Megs or Infinity.

Something definitely is not right. The test indications of an excess load lurking somewhere match up with the observation of the Supply Unit being hit with a massive load with both Dynamotors running in SEND Mode in order to check proper operation of the Receiver Isolation Relay. That prompted a quick shut down of the set as soon as proper function of the relay was heard. A careful visual examination of the Sender shows no heat discolouration anywhere. Nor are there any burnt smells anywhere, and the Supply Unit continues to function nicely with the Sender out of the Carriers No. 4 circuit and on the bench alone.

I do wonder if the Mode of Operation Switch may have a buildup of oxidation on its terminal wafer connections that I missed, so to rule that out, I am going to give that switch a couple of cleanings with Dioxit today and then repeat the set of tests for V7A. Nothing may change, but at least I can rule the possibility out and know the Mode of Operation Switch will now be nice and clean.


David

[David Dunlop]

I was able to give the Mode of Operation switch a couple of good cleanings with Deoxit the other day, which produced some positive results regarding the resistance tests for the V7A (813) Socket Pins.

First, the suspect results on Pin 3 all dropped by nearly 250,000 Ohms and are all now in a quite acceptable range. There was also an improvement in a couple of the readings for Pin 4. One reading should be 40,000 Ohms and I was getting ‘Infinity’ initially. I now get 60,000 Ohms. The second reading is supposed to be 11,000 Ohms and it was also initially giving me ‘Infinity’. It now reads 700,000 Ohms. Neither is acceptable yet, but at least I have hard numbers to work with. Every little improvement helps.

In the course of doing all this work, I stumbled across a mystery on the Circuit Diagram for the Sender, as published by Canadian Marconi on Page 203 of the Operators Manual. Still have not got it all sorted out yet (maybe never will) but I will document it all shortly.

By the way, with regards to Circuit Diagrams for the 52-Set, should you ever need them, trust only those published by Canadian Marconi Company in the Operators Manual for the 52-Set. There is another set out there redrawn and included in an evaluation document for the 52-Set. These ‘copies’ have a lot of missing information and mistakes in them. Not at all reliable for serious repairs or servicing.


David

[David Dunlop]

Having now got the suspect circuits narrowed down from the first Sender Resistance Test, the next step was to trace those circuits out on the Sender Circuit Diagram in the Operators Manual and list out the components found on them. Each component can then be checked out individually to see if any faults show up.

While doing this over the weekend for the Pin 4 circuit of V7A (813), I ran across a couple of small symbols I had never noticed before on the Sender Circuit Diagram. They were basically small little circles with a ‘Dot’ in the middle. The circuit line ran up to the circle and stopped, and 180 degrees opposite, continued on its way. A small number was written to the upper right of each of these circles and I eventually found nine of them. All were located in the front section of the Sender, between the Master Oscillator Tuning and the Power Amplifier. Oddly, there were no Comments, or Notes, to be found anywhere on the Sender Circuit Diagram to explain what these symbols were. No references at all. In fact, the Sender was the only one of the four main components of the 52-Set to have these symbols.

In the past, I have run across similar types of markings on equipment circuit diagrams, but they have always been referenced and turn out to be test points to take Meter or Scope readings at, and the circuit documentation includes values, or images of the results to expect under various circumstances. I bounced the discovery off the 19-Set Group in the UK and they were just as puzzled and came up with similar test point suggestions.

Then last evening, while looking for the components along the Pin 4 circuit for Valve V7A (813), sitting in plain view, was a long thin Panel Strip with four Screw Terminals fitted to it. Stamped into the phenolic board beside each terminal were the numbers 9, 8, 7 and 6 in white paint. My first thought was how odd that they numbered this board backwards. It took a moment or two to sink in the highest number happened to match the highest numbered symbol I had found on the Sender circuit diagram,

So I pulled out the February, 1945 Issue 1 of the Illustrated Parts List and went through the Sender Section looking at all the panels. Eventually, there they were, three of them: 2-Terminal, 3-Terminal and 4-Terminal. All use ANC 8-32 x 5/16-inch binding head Screw Terminals. The challenge was then to find the two smaller ones. Which I eventually did this morning. I will cover them in sequence in separate posts shortly.

One other strong suggestion I have regarding the available 52-Set documentation if you need it to work on a set. Get both the original issue Parts List from 1945 and the revised issue from 1948. In the 1948 version, all the duplicate entries were deleted and the descriptions streamlined. That saved printing costs and reduced the size of the publication, but a lot of useful information was deleted in the process. The 1945 issue listed old and new CMC and ZA Part Numbers. Most old ones were dropped in the 1948 issue. Also, the 1945 version often gave the circuit reference number for parts, like R15A, or C32B, or detailed supporting hardware information. This is largely lost as well in the 1948 version of the Parts List. With this Wireless Set, the more research assets you have on hand, the better.


David

[Bruce Parker (RIP)]

Frikin' amazing Dave.

[David Dunlop]

Of the three of these particular PANELS, this one is the second best hidden on the Sender chassis and I found it when hunting for the components related to Terminal 2. Circuits from V5A, the Master Oscillator/Doubler and V5B, the Amplifier/Doubler are tied into this PANEL. Both of these valves are 6V6G’s.

The three terminals on this panel have their numbers stamped into the phenolic panel and painted white. Terminal 1 is in the upper centre. Terminal 2 is on the lower left and Terminal 3 on the lower right. L33A blocks a good clear view of what is connected to Terminal 1. The CMC Circuit Diagram indicates C27D, the Coupling Capacitor for the V5A Plate, and L32A, the RF Choke for the V5A Plate tie into Terminal 1. Based on the fact the connections for Terminals 2 and 3 on the Circuit Diagram do indeed match what is showing up on these terminals on the actual panel, and that V5A and V5B are giving me no signs of problems so far, I am comfortable assuming all is as it should be with Terminal 1.

Terminal 2 has C11C, the Coupling Capacitor for the V5B Grid, R10A the Parasitic Suppressor for the V5B Grid and L32B the RF Choke for the V5B Grid connected to it.

Terminal 3 is a busy one, being tied to C6C, a Variable Capacitor serving as the V5A Plate Trimmer, C9C, another Variable Capacitor serving for the tuning of the V5A Plate for this valves work as a Doubler. L33A, the 3.5 – 8 MC Tank Coil for the V5A Plate and C28A, the Padder Capacitor, are also associated with this terminal.

The attached photo shows how this PANEL is tucked in behind L33A in the Sender chassis.

My apologies for all the electronic banter in this set of posts. Not knowing yet, how much information is still around in the 52-Set documentation, I thought it might be prudent to put as much information about these three panels down here, while I can, just in case.

One down. Two to go.



David

[Bruce MacMillan]

Originally Posted by David Dunlop

My apologies for all the electronic banter in this set of posts. Not knowing yet, how much information is still around in the 52-Set documentation, I thought it might be prudent to put as much information about these three panels down here, while I can, just in case.

One down. Two to go.
David

Keep it up, more is better than less. I assume all this info will be in the definitive 52 set restoration guide when you publish it!

[David Dunlop]

Thanks for your comments Bruce. This project has some alarmingly slow moments so I am not certain if the publication you suggest will be doable once this 52-Set is finished and back on the air. Even factoring in the philosophical question as to whether or not any project is ever truly finished.

Not only is this the smallest of these three PANELS, it is the most miserably hidden on the Sender Chassis.

As noted in my earlier post of the illustrations of the three PANELS, if looked at right side up, the left side Screw Terminal has a white ‘5’ stamped into the panel to the upper right of the terminal. The right side Screw Terminal has the white ‘4’ stamped into the panel at the lower left of the terminal. Are you confused yet?

This small panel is located in the bottom front left corner of the Sender Chassis, just above the bank of three coils, L35A, L33B and L36A. You will first notice the wafers of the R.F. Driver Band Change Switch, S13A, and then catch sight of this panel tucked well in behind it.

According to the Sender Circuit Diagram, Terminal 4 links between C27E, the V5B Plate Coupling Capacitor and Switch S13A. In turn, Terminal 5 joins Switch S13A to C8E, the V5C Grid Coupling Capacitor, R10B the V5C Grid Parasitic Suppressor and Pin 5 Grid 1 Circuit of V5C (6V6G) the Intermediate Power Amplifier. I can make out R10B coming off Pin 5 of the V5C socket and going to Pin 1, which is being used as a connection tag, and that is pretty much it for certain, without a major disassembly being undertaken. Once again, I am assuming all is correct and OK with these circuits as I am getting good, normal test results from V5B and V5C so far.

The attached photo gives you an idea of how nicely hidden this panel is on the Sender chassis. You can see the screw of Terminal 5 to the left, the two smaller, round head mounting screws, one above the other in the middle of the panel and just make out part of the Terminal 4 screw peeking out on the right.

One left to go.


David

[David Dunlop]

As I noted back in Post #859, it took a little while to ‘connect the dots’ between the strange set of nine numbered symbols I had first noticed on the Sender Circuit Diagram on Page 203 of the 52-Set Operators Manual, and the actual hardware mounted in the Sender chassis. It was this particular panel, hiding in plain sight, that I finally saw for the first time and allowed me to understand the symbols. The attached photo clearly shows how obvious this panel actually is, if ones eyes are truly open.

I still do not know why these four terminals had to be numbered in reverse order, but they were. This photo also shows the stamped numbers in the phenolic panel very well (common to all three such panels) as well as how the ring terminals and sleeves are set up on the wires connected to the terminals. This feature is also common to all three panels.

Terminal 6 is set up between S13A and C8D, the Grid Coupling Capacitor for V7A (813), L34B, the V7A Grid RF Choke, C26G, the V7A Grid RF Bypass Capacitor and S16A, the Mode of Operation Switch. Also tied into it is R8A, the Parasitic Suppressor feeding to Pin 4 (Grid No. 1) on V7A. This all caught my attention since the Pin 4 circuits are giving me the bulk of the bad readings for V7A at the moment.

Terminal 7 is between S13A and C27F on Pin 3 of V5C, the Plate Coupling Capacitor, L43A, the V5C Grid 7 – 16 MC Tank Coil, and C17A, the variable V5C Plate Tuning Capacitor.

Terminal 8 is between S13A and L34C, the V5C Grid RF Choke, C27F on Pin 3 of V5C, the Plate Coupling Capacitor, and R39C, the V5C Screen Voltage Dropping Resister, and R7E, the V5C Screen Parasitic Suppressor on Pin 4 of V5C.

Terminal 9 is the last of this series of screw terminals. It is situated between S13A and R57A and R57B, a series set of 600,000 Ohm HT Metering Resisters, and C26H, the V7A Screen RF Bypass Capacitor connected to Pin 3 (Grid No. 2) on V7A. This circuit is now also of interest since the meter reading for the Sender HT Circuit was only giving me 110 Volts DC (+/-) when the Supply Unit was running, and the actual readings should be either 300, or 600 Volts DC, dependant on whether one, or both of the Supply Unit Dynamotors are running.
So it looks like the time it took to trace out what these nine terminals are doing in the Sender was a worthwhile effort as it gave me a better focus on where two of the major problems with the Sender circuits might be located.

David

[David Dunlop]

This last photo of the underside of the Sender chassis actually covers where all three of the just discussed screw terminal panels are located.

As you can see, the 4-Terminal panel jumps right out at you when you know what you are looking for, but the 2-Terminal panel in the section just below it is a lot harder to find and recognize. And in between these two in terms of ease of recognition, is the 3-Terminal panel tucked down in the lower right corner, behind the L33A coil.

Why Canadian Marconi Company used these three panels where they did, I still do not understand. I like the idea Chris put forward that it may have provided advantages on various parts of the assembly line for subcomponent assembly and testing, before these items were delivered to the main assembly line for actual installation into the Sender chassis units. There does not seem to be much advantage to them for subsequent maintenance or servicing at the moment. As Jacques Fortin said when I brought them to his attention, if no further information turns up, they shall be added to the CMC List of Secrets for the 52-Set.


David

[David Dunlop]

Before I plod along any further, I just want to correct an error on my part in terminology.

Over the last few posts on the three screw terminal panels, I had been referring to the fittings attached to these panels as ‘Ring Terminals’. I became suspect of that identification this morning and decided to confirm what they are more closely.

As per the attached photo, these fittings are actually ‘Fork Connectors’, but of a type I cannot recall ever seeing a modern equivalent of in any electronic supply shops today. Note that the inner throat of the fork is designed to also serve as an integral lock washer.


David

[David Dunlop]

A short and good week so far.

I received a phone call from Anything Custom, a local machine shop, on Tuesday advising two small items I had asked them to fabricate for this project, were ready for pickup.

This particular item used to be a 3.5-inch long piece of ½-inch copper water pipe. I needed it to be pressed flat to form a small copper buss bar that will serve as the key part to a Ground Terminal for my wireless equipment.


David

[David Dunlop]

Going all the way back to the 1970’s, I have never bothered hooking my two Wireless Sets No. 19 to a Ground Terminal when operating them, in spite of recommendations to do so in the various 19-Set manuals. My excuse was always that it was too much work to run a proper Ground Line into the part of the basement the wireless equipment was set up in.

That changed a couple of years back when the bathroom next door was renovated. I actually took the time to take advantage of opened walls and ceilings to run a continuous transmission cable in from the aerial in the back yard to the wireless equipment, and also a proper ground line. As far as I got at the time with the Ground Line was a foot long lead of copper wire poking through the wall under my wireless bench and a running idea of how I wanted two related terminals set up.

With the 52-Set being the powerhouse it is, I finally caved and decided to get this Ground Terminal completed and ensure all future operation of either the 19-Sets, or the 52-Set will be done with the equipment properly grounded.

So, in addition to the piece of water pipe that has now been flattened, the attached brass hardware and 4-inch square, plastic electrical box have been added to the parts to complete this Ground Terminals sub-project.


David

[David Dunlop]

This was the second small item I had fabricated at Anything Custom.

It is a replica of the bracket removed from the right rear wall of the tool box and it would have supported the right hand end of the wooden Hydrometer Storage Case.

Once I have drilled the mounting hole and given the bracket an aged patina I will install it.

I you want to recap the story of this tool box, I starts with its discovery and arrival back in May, 2018 (Posts #65 - 69), refabrication of the missing wooden partition (Posts #321 - 323), in 2020 and a test fit of the Irons, Soldering in Post #403.


David

[David Dunlop]

This morning was spent marking out and drilling the three holes in the copper bar, for my Ground Terminal Project. The hardware is all ¼-inch brass, but I went to 17/64-inch for the hole size, just to make assembly a little easier.

Once the holes were in the copper bar, I used the bar as a template for getting the two terminal post holes properly centered on the cover of the electrical box.


David