It was a stressful, but productive evening yesterday. I ended up spending it with my ears tuned to the sump pump in the furnace room, listening to hear if it would kick in, while my eyes were on my VTVM, getting the testing completed for the second Sender Resistance Tests.
I should take the time here to clarify a few points. All three resistance tests require the valves to be removed from the Sender chassis. The first test was a basic pin by pin check from each valve socket to ground, with, from time to time, the Mode of Operation Switch and the Power Switch in specific positions. This second set of resistance tests is taken from each of the terminals on the two 8-pin Connectors on the upper rear of the Sender, and the 7 terminals on T3A, the Modulation Transformer for the V5D Plate. Again, all readings are to ground and from time to time, the Mode of Operation Switch, Power Switch (and this time) Sender Meter Switch must be in specific positions. A total of 52 tests are involved in this set.
On the first work through, I found 21 results that were suspicious, so last evening, I focused solely on redoing all of these with the VTVM and randomly spot checking a few of the others to see if they were reliable. When all was said and done, two of the 21 tests reexamined now produced good, normal results and are now off the ‘Red Flag List’. For the remainder, all of the ‘Infinity’ readings disappeared and I got good solid resistance values back for my efforts. These are all higher than they should be, and a few are alarmingly so, but it is all data I can work with now.
It is still too early to know exactly what is going on in this Sender, but one interesting observation so far is that when the Mode of Operation Switch is in RT Mode, this seems to produce more than its share of very high readings, when compared to CW, M.C.W. and BREAK IN Modes.
In the meantime, I will try and get the last Sender resistance Test redone today.
David
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