Wireless Set No. 52 Canadian - Project

[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.