Wireless Set No. 52 Canadian - Project

[Bruce Parker (RIP)]

I'm not sure khaki is inconsistent. Radio colours matched truck colours to a degree, the big differences being that early radio equipment had a dark green that wasn't matched on vehicles, and I'm pretty certain no radio gear was ever painted 'light stone' from the factory. A good deal of mid war radio ancillary parts (spares and parts boxes, splitters, signal lamp battery boxes come to mind) were khaki, as were trucks prior to 1943.

Originally Posted by David Dunlop

With the assistance of Jacques Fortin, I was able to find an original replacement C25A/B capacitor for the Remote Supply. It should arrive next week and it will be great to get that portion of the project back on track.

In the meantime, I have been reading through the 2” binder of 52-Set manuals I have accumulated, and realizing I should have purchased a 3” binder, as more documentation keeps popping up.

In the process, a mystery has surfaced in the Master Parts Identification List for the 52-Set, that I want to put out to everyone for review. I will preface that comment by stating whoever did the proofreading for this document back in 1944-1945 did a great job. Quite a few corrections are noted in the descriptions. As an example, the canvas cover that rolls down over the front of the Carrier Assembly should be correctly identified on the front of it as a ‘COVER’, but some early production of the item marked it as a ‘CURTAIN’ and that term is to be disregarded.

Now to the mystery. My understanding of the 52-Set production run from CMC, is that the early sets were finished in the same wrinkle olive green as the preceding Wireless Set No. 9 Mk I Cdn. This was then switched to No. 2 Brown wrinkle finish, which covered the bulk of the production run. Finally, there is the possibility that the colour switched back to wrinkle olive green close to the end of the production run.

Where it gets interesting in the Illustrated Parts List is that the colour ‘Khaki’ is mentioned for the finish on the three spare parts and tool boxes and once for the case used on the Remote Receiver. In another location the Remote Receiver Case is referenced as being ‘Brown’ . The Main Set Carrier is always referenced as ‘Brown’.
The canvas carrier cover previously mentioned is always referred to as ‘Brown’.

The Serial Numbers of the parts I have found run from the high 7,000 range to the high 8,000 range. The interior of the ATU I received from Bruce Parker is finished in No. 2 Brown, and it has the SN 8963, so I am confident that if all relevant parts are eventually finished in wrinkle, or flat, No. 2 Brown, I will be OK. And a brown canvas for the cover should be easy enough to track down. But the reference to ‘Khaki’ puzzles me. I do not recall ever seeing it as a reference colour before on anything vehicle or signals equipment related, other than canvas goods. No. 2 Brown is so distinctly brown it seems hard to think it would be called anything else, so I am thinking ‘Khaki’ must be an error.


David

[David Dunlop]

This little gem arrived earlier in the week from Jacques Fortin and I would like to thank him on two counts. First, for the presence of mind a number of years ago to carefully disassemble a surplus remote supply unit and save the parts, rather than simply tossing the entire item. And secondly, for taking the time to search his parts to locate it and make it available to me.

Factory rated for 20uF on both sides when new, it currently checks out at 21uF and 27uF. I can now desolder the suspect capacitor in my ZE-11 Remote Supply and test it against this one to see which one is healthier. I was reluctant to pull the existing cap until I knew I had a suitable replacement, so that all potential work could be done in one sitting. A necessary consideration when dealing with an electronics work bench that is not cat proof.

David

[David Dunlop]

Well, long story short, I was able to successfully reform the wonky capacitor pair on the weekend and everything in the circuit downstream of the OZ4 rectifier is now in good working order.

That being said, however, a new problem has now been revealed. The input voltage to the OZ4 is not balanced for some reason. 50V too low on one side. More investigations ahead I fear. Sigh!

David

[Chris Suslowicz]

Originally Posted by David Dunlop

Well, long story short, I was able to successfully reform the wonky capacitor pair on the weekend and everything in the circuit downstream of the OZ4 rectifier is now in good working order.

That being said, however, a new problem has now been revealed. The input voltage to the OZ4 is not balanced for some reason. 50V too low on one side. More investigations ahead I fear. Sigh!

David

Is the correct vibrator fitted? If it's a series type (as used in the WS19 Supply Unit No.2) then the coil will drop some of the voltage to one half of the transformer primary - and the centre-tap is not in the centre on that supply unit to account for this. You probably need to fit a shunt vibrator (he said, without looking at the circuit diagram).

Chris.

[David Dunlop]

Hello Chris.

Interesting you should comment on the vibrator.

When I first took a look at the circuit diagram for the ZE-11 Supply, I assumed the two options for input (12V DC Battery, or, 115/230 V AC Mains) were fully exclusive of one another based on placement of the 6-pin Plug and the spring loaded switch setup. The current vibrator could very well be the factory original one. It is completely generic in look, with only “12 V” and the Canadian Marconi Part Number stencilled on the end of it in black block letters. It is also dead.

I did not worry too much about the vibrator status as I reasoned that since it was isolated by choosing the AC Mode of operation, and my sole intent was to be using the ZE-11 as a Mains based supply for the Remote Receiver, all would be OK.

Having solved the C25A/B capacitor problem and knowing I now had a good working OZ4 in the system, everything checked out OK downstream of the OZ4 socket. But when connected to the AC Mains, I now discovered the input voltages to pins 3 and 5 of the OZ4 are not matched. I am getting 200V AC on one side and 150V AC on the other. Should be 200V each. The end result is just 7 V DC at the HT pin on the Jones Socket, instead of the expected 150 V. I am also getting strange, intermittent voltage spikes ranging randomly from 10 to 51 volts, with an immediate return to the baseline 7 volts.

The first two things that came to mind were that the secondary windings on the transformer for the AC side had gone, but it was also possible that one of the RF Choke pairing L13A, L13B had shorted. The only way I can see to test which option is correct is to dismount the RF Choke can on the side of the chassis to exposed the two terminals feeding from the transformer. If the two feeds from the transformer are feeding 200 volts AC, then one of the chokes has failed. Worst case scenario, the secondary on the transformer is shot.

Then it crossed my mind the dead vibrator might be a factor, if it is still active in some way even when the supply is in AC Mode. Still trying to sort that out in my head. The price I am paying from being away from electronics for 30 years. I do know that if the vibrator is in the socket, or removed, there is no change in the results I am getting at the Jones Socket. A good working order vibrator could clarify that for me. The manual specs it out as follows:

VIBRATORS, Non-Sync. 12V, 4-Amp 1-1/2 inch diam, 3-1/4 inch long.

Not sure off the top of my head if that is a match for the one used in the 19-Set Supply, but it is a convenient point to take some time to mull over, with a stiff drink.

David

[Bruce MacMillan]

Looking at the xfmr secondary the centre tap goes to ground. Unplug the OZ4 and measure resistance from pins 3 & 5 to ground. This will include the resistance of the chokes. I wouldn't think there should be a lot of difference. If there is then disconnect the chokes and measure the voltage on the xfmr secondary to see if different. Hopefully not a shorted winding.

The DC side is separate from the AC side with the exception of R35A and R35B loading the vibrator winding to ground. The schematic shows each is 300R 5%. A good vibrator has no effect when running with AC and that is why it can be left in situ.

The primary side of this psu is almost identical to the VP-3 psu used with the Marconi CSR5 receiver. Vibrator used is nonsynchronous 115 cycle p/n 111-131.

[David Dunlop]

Thanks for clarifying the status of the vibrator in the overall system, Bruce. I will ignore it for the time being.

I pulled the OZ4 and checked the input to it on pins 3 and 5. Pin 3 was 200 VAC. Pin 5 was 150 VAC. As I reached under the supply to switch it off, I caught a bit of movement under some of the wiring. Loose bits wreaking havoc perhaps? When I turned the supply upright and gave it a careful shake over the bench, a small, oxidized blob of solder, along with several blobs of what looked like molten graphite fell out. I then blew the chassis with the air gun to make sure nothing else was still hiding.

When I then repeated the aforementioned test, I got 200 VAC on both Pin 3 and Pin 5. With the OZ4 still out, and the supply turned off I decided to double check the output from Pin 8 on the OZ4 to the HT terminal on the Jones Plug. A DC Voltage sweep from 10 to 150 Volts fed into Pin 8 was mirrored perfectly at the Jones Plug.

Next step was to reinstall all three OZ4s I have, fire up the supply and see what HT outputs arrived at the Jones Plug for each of them. Two had a ‘Nil’ result, the third gave me 7 VDC.

Looks like checked and matched OZ4s and OZ4As are readily available on eBay. Will have to pick a few up and try them out. From what I can now see with this ZE-11, a good OZ4/A should bring the AC Side of the supply to life just fine.

David