[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