Wireless Set No. 52 Canadian - Project

[David Dunlop]

With an even mix of curiosity and trepidation, I decided on a simple test of the 52-Set this evening.

I warmed up the Receiver and Sender Heater circuits for nine minutes, took a deep breath and switched on the Netting circuit for the Sender. This activates only the MG1A (300 Volt Dynamotor).

A constant sniffing of the air at the Sender Blower Door showed no sign of a smoke smell and a nice subtle ozone smell from the Supply Unit Blower was evident. After two minutes running, all was still well.

This at least tells me the problem is somewhere in the 1200 Volt circuits of the Sender.

Every little bit of information helps.

David

[David Dunlop]

I pulled the Sender out of the Carriers No. 4 this afternoon and got it on the bench. 20 minutes later, after a careful visual examination, I could see, or smell, no trace anywhere of recent overheating.

Next step will be removal of all the valves and a complete redo of the three resistance tests for the Sender using the same VTVM I did the original tests with earlier this year. This was something I had planned to do anyway after carefully cycling the 300 and 1200 Volt power feeds from the Supply Unit though the Sender over a period of time.

There were a cluster of unusually high resistance readings in the first tests I am curious to see any possible changes in. Also, I may now find an earlier, normal resistance value that has suddenly gone south, which might point to the potential new problem. It will take a few days to complete, since access to a few of the test points required temporary unfastening and moving of some components.

David

[David Dunlop]

A rather nice parcel arrived in the mail today from Alberta.

This particular Curtain, Waterproof is a replica, made over 20 years ago by an Edmonton tentmaker, copied from a borrowed, surviving original at that time. They could not get a perfect match to the original colour of green canvas from available stocks and the weight is slightly lighter than the original as well. What I liked, however, is they matched to the nickel plated hardware on the original.

I do not know where the original Curtain, Waterproof came from, or ever ended up, but at least we know it was still surviving a while ago.

While installing it to warm up and hang, I discovered the rightmost Lift The Dot post riveted to the top of my Carriers No. 4 has been bend slightly to the right. Surprisingly, the post itself seems to be OK. The bend had taken place in the upper sheet steel of the Carriers No. 4. With a little TLC down the road, I might be able to dolly the sheet metal back level. Added to the ‘To Do’ List in any event.


David

[David Dunlop]

Thought I had better show a photo of the Curtain, Waterproof rolled up in the stored position on top of the Carriers No. 4, while I have the Sender out for testing. Notice how it forms a smooth, cylindrical tube when fastened down.

Anyone with an original Curtain, Waterproof can probably confirm this, but the smooth look of this curtain in the stowed position is very likely due to the fact it is a replica made from a bolt of canvas that has not been treated with the usual paraffin and wax solution to actually waterproof it. You will notice in the first photo of my previous post, when in the deployed position, the weight of the steel bar in the bottom edge also holds the canvas in a smooth tight sheet.

I noticed these effects last evening and checked the waterproof covers on my Mk II 19-Set and Variometer and my Mk III mounted on the Carriers No. 23. All three of these canvas items are very stiff, you can still smell the waterproofing when they get warm and they only ever really 'relax' when they get warm.

I don't think I will ever bother to apply any traditional waterproofing to this replica, but I might give it a spray of silica boot waterproofing, just to validate the name of the curtain, if nothing else.


David

[David Dunlop]

The 3rd set of resistance tests for the Sender were completed yesterday and overall, the results were very consistent with the two sets of tests run last Spring.

Of none electrical note, the rust on my VTVM Testing Procedures is now shedding in huge chunks. Most of the red flag readings I took earlier that were ‘Infinity’ in nature produced excessively high, but real values this time around. This was primarily due to me focusing on taking advantage of the different testing ranges on the meter to see if and where I might actually get a useful reading. It is amazing what one can forget when being an infrequent user of helpful equipment.

The majority of the good readings were either identical to the earlier ones, or +/- very, very close, so that was nice to see as well. The red flags are all clustered in the same circuits as earlier and the other big plus was nothing new showed up that might have been related to the overheating event that happened a few weeks back, so I have inflicted no new damage…so far.

The dark side of all this, however, is my next step in the process. I now have to go back to the Sender Circuit Diagram and methodically trace out each red flag circuit to identify all the related components. There are likely a few resistors that have dropped off in value, but most of the problems are probably going to be with the PIO Capacitors that have transformed themselves into resistors. The problem now though is the 52-Set Circuit Diagram for the Sender is very compact for easy reading/tracing. One sooner or later has to resort to using a magnifying glass, or lamp, which narrows down your field of view, compounding the problem. A whole different experience from working with 19-Set diagrams.

The challenges don’t stop there either. Once I have identified all the components that need further investigation, I have to find them on the chassis and test each. The ones tied to valve socket terminals are the easy ones. It is the remote ones tied to a terminal panel, tucked behind another component, six inches away that create the nightmares.

Good thing it is a long Winter in these parts.


David

[David Dunlop]

As expected, and not withstanding current seasonal activities, the analytical work involved in tracking down problems identified in testing electronics is moving painfully slow for me. The price I pay, I suppose for not doing enough of it over the last few decades. In any event, progress is actually being made.

The initial point of interest was that across all three resistance tests, the problem results were nearly all of excessively high values, and most were directly related to tests in which the Mode of Operation Switch on the Sender was set to the R.T. Mode. A number of these results, of course, showed up with Pin to Ground readings for the 813, which was a little scary initially. Then I finally realized the Speech Circuit would be the common factor across all these problem results.

The Speech Amplifier in the Sender is V1J, an ARP-3 Valve, and in close relation to it is V5D, the Modulator, the position of which is taken up by a 6V6G Valve.

In the tests result, V5D, showed no real problems and it shares some of the circuit components of V1J. V1J, on the other hand showed good results until tests involved it be active in the RT Mode and then results went off the charts. So V1J now has my undivided attention.

The two problem circuits for V1J include 3 capacitors, one of which is electrolytic, and 5 resistors. One of those resistors shows normal values off RT Mode and three of the others are shared when required by V5D, so may be OK. The stage of my work now, is finding where all eight of these components are located on the actual chassis and testing each individually. An interesting challenge in its own right.

In the two photos today, the first shows the V1J socket at the bottom, partially hidden by the T2A transformer (easily removable), with the V5D socket directly above it. I suspect all of the components needing examination will be either tied directly to the pins of these two sockets or hiding somewhere along the board in the second photo which is fastened to the lower rear edge of the Sender chassis with three screws.

Hard to do, I know, but it would have been nice if the capacitors could have been mounted on the boards with the useful specs data showing. I have found more than enough in 19-Sets and other equipment, including this 52-Set, where the only readable information is the capacitor makers name or “MADE IN CANADA” and the side with the critical specs is securely fixed against the circuit board.

The journey continues.


David

[Chris Suslowicz]

Originally Posted by David Dunlop

As expected, and not withstanding current seasonal activities, the analytical work involved in tracking down problems identified in testing electronics is moving painfully slow for me. The price I pay, I suppose for not doing enough of it over the last few decades. In any event, progress is actually being made.

The initial point of interest was that across all three resistance tests, the problem results were nearly all of excessively high values, and most were directly related to tests in which the Mode of Operation Switch on the Sender was set to the R.T. Mode. A number of these results, of course, showed up with Pin to Ground readings for the 813, which was a little scary initially. Then I finally realized the Speech Circuit would be the common factor across all these problem results.

(Snipped a bit.)

The two problem circuits for V1J include 3 capacitors, one of which is electrolytic, and 5 resistors. One of those resistors shows normal values off RT Mode and three of the others are shared when required by V5D, so may be OK. The stage of my work now, is finding where all eight of these components are located on the actual chassis and testing each individually. An interesting challenge in its own right.

High values in the resistance tests will not be caused by faulty capacitors - they should have infinite resistance (waxed paper/paper in oil/ceramic/silver mica types) or a low resistance that increases rapidly as they charge up (electrolytics). Capacitor failures are usually low resistance (electrolytics where the oxide dielectric layer has dissolved), moisture entry (waxed paper), or short circuits (silver mica), or else open circuit failures. High resistances are more likely due to resistor ageing or dirt/corrosion on switch and relay contacts - so it's worth using switch cleaner on those if the results of the testing are "off" in one position.

Capacitors should be checked for low resistances (may need to lift the wire at one end so you're only testing the capacitor and not any associated resistors), and reformed (electrolytic types) or replaced (all types) if leaky.

Hard to do, I know, but it would have been nice if the capacitors could have been mounted on the boards with the useful specs data showing. I have found more than enough in 19-Sets and other equipment, including this 52-Set, where the only readable information is the capacitor makers name or “MADE IN CANADA” and the side with the critical specs is securely fixed against the circuit board.

The "PC" number is visible on a lot of them though, so if you've got the actual parts list that will tell you the value and rating. PC = Procurement Catalog(ue), and it's common to all equipment so you can use the numbers from the WS19 if they're in that manual.

It might be worth making a list of PC numbers and the specification as you work through the restoration - looking up visible numbers is a lot easier than dismantling the set to get at the hidden side (though you may need to do that anyway if it's faulty and has to be replaced).

Best regards,
Chris.