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Old 08-05-22, 23:31
David Dunlop David Dunlop is offline
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Location: Winnipeg, MB
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Having now got the suspect circuits narrowed down from the first Sender Resistance Test, the next step was to trace those circuits out on the Sender Circuit Diagram in the Operators Manual and list out the components found on them. Each component can then be checked out individually to see if any faults show up.

While doing this over the weekend for the Pin 4 circuit of V7A (813), I ran across a couple of small symbols I had never noticed before on the Sender Circuit Diagram. They were basically small little circles with a ‘Dot’ in the middle. The circuit line ran up to the circle and stopped, and 180 degrees opposite, continued on its way. A small number was written to the upper right of each of these circles and I eventually found nine of them. All were located in the front section of the Sender, between the Master Oscillator Tuning and the Power Amplifier. Oddly, there were no Comments, or Notes, to be found anywhere on the Sender Circuit Diagram to explain what these symbols were. No references at all. In fact, the Sender was the only one of the four main components of the 52-Set to have these symbols.

In the past, I have run across similar types of markings on equipment circuit diagrams, but they have always been referenced and turn out to be test points to take Meter or Scope readings at, and the circuit documentation includes values, or images of the results to expect under various circumstances. I bounced the discovery off the 19-Set Group in the UK and they were just as puzzled and came up with similar test point suggestions.

Then last evening, while looking for the components along the Pin 4 circuit for Valve V7A (813), sitting in plain view, was a long thin Panel Strip with four Screw Terminals fitted to it. Stamped into the phenolic board beside each terminal were the numbers 9, 8, 7 and 6 in white paint. My first thought was how odd that they numbered this board backwards. It took a moment or two to sink in the highest number happened to match the highest numbered symbol I had found on the Sender circuit diagram,

So I pulled out the February, 1945 Issue 1 of the Illustrated Parts List and went through the Sender Section looking at all the panels. Eventually, there they were, three of them: 2-Terminal, 3-Terminal and 4-Terminal. All use ANC 8-32 x 5/16-inch binding head Screw Terminals. The challenge was then to find the two smaller ones. Which I eventually did this morning. I will cover them in sequence in separate posts shortly.

One other strong suggestion I have regarding the available 52-Set documentation if you need it to work on a set. Get both the original issue Parts List from 1945 and the revised issue from 1948. In the 1948 version, all the duplicate entries were deleted and the descriptions streamlined. That saved printing costs and reduced the size of the publication, but a lot of useful information was deleted in the process. The 1945 issue listed old and new CMC and ZA Part Numbers. Most old ones were dropped in the 1948 issue. Also, the 1945 version often gave the circuit reference number for parts, like R15A, or C32B, or detailed supporting hardware information. This is largely lost as well in the 1948 version of the Parts List. With this Wireless Set, the more research assets you have on hand, the better.


David
Attached Thumbnails
Sender Screw Terminal Panels.jpg  

Last edited by David Dunlop; 09-05-22 at 00:55.
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