Hi Bob.
Thanks for your kind words.
Generally, I start by looking at the circuit diagrams top ID electrolytic caps first. After prolonged inactivity, they lose these ability to hold a charge and become “resistors” shutting down the circuits they are in. If I find any such circuits in the diagrams, a resistance test will show an abnormally high reading and voltage flow will be limited. Might even got no continuity.
Then I try a Variable DC Power Supply on the circuit and monitor milliamp responses to a slow series of voltage increases to see if the electrolytic cap can be reformed and get the circuit back to normal. I will then check the resistors to see what ones might be off tolerances enough to be impacting function. Replacing these today usually means going up in value. a 300 Ohm resistor with 10% tolerance may mean having to use a 330 Ohm modern replacement, which would be at the upper working limits of the original. That is OK. Also might have to move from a 1/2-Watt rating to a 1-Watt rating only to keep the replacement looking close in size to the originals in the set.
I have not done much cap replacement yet, but it is coming. I hope to “stuff” the original carbord sleeves with modern equivalent axial caps, again, so the originl look of the chassis guts stays the same. Seems to be several ways of doing this out there right now that I need to explore more closely.
A common big problem today is overall axial length, end to end of leads, for both caps and resistors. They have all gotten a lot shorter. Tag Board terminals in the 52-Set are 2.5 inches or 3.0 inches apart. Wartime components had overall lengths of 4.0 inches. The leads were fitted to the Tag Board terminals, (either threaded in, or wrapped), soldered in place, and then excess leads trimmed. This line work usually took place on the Tag Boards alone. Any required wiring loo,s would then be added and the finished items would later be fitted to the chassis down the line. A lot more accessible to work on than the finished products todays. However, most of these Tag Boards can be carefully unmounted from their chassis locations and made more accessible to work on.
Modern components seem to be just 2.75 inches overall length. Not good.
I have never worried about heat sinks. Solder has an effective working temperature range. I set my iron to the midpoint and have never had a problem with the quality of the finished solder work. If original leads have factory spaggetti, I always transfer it to replacement parts. The factory team at Canadian Marconi Company knew more about putting these sets together than I ever will, so I just follow their lead in that regard.
Also, I rarely use modern test equipment. Most is 80 to 50 year old tube driven equipment, consistent with the technical era of the wireless sets I work on. That test equipment told the designers of these sets they worked very well, and they did. That is good enough for me and I have no interest in chasing “faults” modern test equipment might identify.
I also have a number of friends across the country with far more electronics and amateur radio experience that I will ever be able to achieve. Whenever I hit a wall working on this equipment, I reach out to consult, and that help is always very much appreciated.
Anyway, Bob, I natter. Hope this helps a bit with your questions.
Cheers,
David
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