Wireless Set No. 52 Canadian - Project

[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

[David Dunlop]

Hmmm.

There is also the possibility I get 200 VAC both sides under a no load condition with the OZ4 out of the system, but add it back and something upstream suddenly cannot handle it.


David

[David Dunlop]

This project is an interesting one on a number of levels, not the least of which is making it work with a limited budget. To that end, at the very beginning, I decided to put together a list of what was required to make the project possible. It became evident very quickly that some items were more important than others, so an A-List and a B-List of required items were developed.

Obviously, the A-List had to include the five basic components of the Main 52-Set Assembly: Receiver, PSU, Sender, Carriers No.4 and ATU. In addition, a Remote Receiver, Remote Supply and relevant Connector Cable were added to this list at critical items.

The B-List became essentially the three Cases/Boxes used for tools, spare parts and the items for the Remote Receiver System. All the accessories common to the 19-Set, and the specialty cables and connectors were added to this list as well as the necessary tools and spares.

Restoration work has been focusing up until now on getting the Remote Supply up and running in order to facilitate getting the two receivers in the complete basic 52-Set up and running. That has been going relatively smoothly but work has reached a point where a lot of little fiddly things need attention, and in most cases, purchases of items to continue with the Remote Supply restoration. A point has been reached, however, where continuing to chase parts for this portion of the project can negatively influence the critical focus of obtaining the A-List items.

They say exceptions prove the rule. Well, I think that is true. I received an email from Jordan Baker a couple of weeks ago telling me he had spotted an interesting box at a location he had recently visited and upon closer inspection, it turned out to be the wooden tool box for the main 52-Set, so he purchased it and got in touch with me. Something had made me set aside the Remote Supply work for the time being just a few days prior to Jordan’s email. True, the box is not on the A-List, but it was one of the three critical, high priority items on my B-List, so I purchased it from Jordan.

It arrived in the mail Monday afternoon and is in very nice condition. A wooden partition on the left hand side has been removed (with considerable care) and will be an easy piece to replicate and replace. I even have a supply of the correct sized finishing nails needed. A metal bracket has been removed from the right rear inner wall, just below the right hinge. Looks like a single piece of hardware held it in place. Form and function remain a mystery for the time being.

Finish is the same OD Green Marconi used on the WS-No. 9 equipment and the Crystal Calibrator for the 19-Set. The two latches are identical to the ones used to secure the cover on the ZE-11 and ZE-12 Remote Supplies and the metal handle on the lid of the box is identical to the two Marconi used on the sides of the Remote Receiver Case. Post War NATO Green paint has been applied to the outside of this box at some point in time, but I can see traces of white markings showing through on the front of the box that will get a closer look shortly.

The photos are courtesy of Jordan, by the way.

David