Wireless Set No. 52 Canadian - Project

[David Dunlop]

Thanks for posting that link, Bruce.

Looks like I will be able to do some more research reading this weekend.


David

[David Dunlop]

Earlier this evening, I finally found the last component I needed to investigate related to the abnormal test results I was getting for the V1J Speech Amp circuits in the Sender.

The component was resistor R49A, related to the V1J Plate Load and I had to remove the T2A Transformer, once again, from the rear skirt of the Sender chassis to reveal its location. I had suspected it was hiding back there at the very start of this quest, and had actually looked with a small, flexible mirror behind T2A, to no avail, so I went on to track down all the ‘easy’ stuff first. More on that later.

In any event, to save anyone else hunting for this resistor down the road, here is a photo of what it looks like and where it hides. It is rated at 100 KOhms, with a +/- 20% tolerance at 1/2-Watt. This one tests out at 126.4 KOhms, so is now on my “To Be Replaced” List.


David

[David Dunlop]

All of the required resistors have now been tested and I have just started looking into the capacitors. To complete that portion, I will need to remove the circuit board mounted on the rear chassis skirt, shown in the second photo in Post #949, and I will have to study that setup a bit first, before removing the three mounting screws holding it in place.

I also discovered that it is possible to carefully spin the cardboard sleeves on those four capacitors around their metal cores, so I was able to wipe all the dust and dirt off them all and expose the sides showing their PC-Numbers and Stats. In addition, as Chris had suggested, I was able to ID two of these capacitors by cross reference to the 19-Set Documentation. So now all four of them are identified

I will sort the resistor results shortly and post them


David

[David Dunlop]

Here are the 10 Resistors in the V1J and V5D Circuits I have been looking into. The data is in order of Circuit Reference, Rating, Tolerance, Circuit and Test Result.

R12A, 250-1/2, 20, T2A Primary Feedback Voltage Div, Tested 8 Ohms *
R16A, 400-1, 20, V5D Cathode Bias, Tested 560 Ohms *
R27D, 5,000-1/4, 20, V1J Cathode Bias, Tested 5,480 Ohms *
R31D, 10,000-1/4, 20, T3A Tertiary Feedback Voltage Div, Tested 8 Ohms *
R37A, 10,000-20, 20, V5A Screen Voltage Dropping, Tested 10,000 Ohms
R41B, 20,000-1/2, 20, V1J Plate Decoupling, Tested 23,070 Ohms *
R46A, 40,000-1, 15, V5D Screen Voltage Dropping, Tested 40,000 Ohms
R49A, 100,000-1/2, 20, V1J Plate Load, Tested 126,400 Ohms *
R56E, 500,000-1/4, 15, V1J Screen Decoupling, Tested 590,000 Ohms *
R61A, 1 Meg-1/4, 20, V5D Grid Leak, Tested 1.178 Meg Ohms *


* To be sourced for replacement.

And the Saga continues.


David

[David Dunlop]

I sent a copy of my testing results to Jacques Fortin the other day and he provided me with some very useful feedback.

First, he pointed out I had missed a couple of resistors in the V1J and V5D circuits I was looking at (R29B and R47C). I am on the hunt for them now and will report back on what I find.

The second issue he brought to my attention was regarding the results for R12A and R31D. Both of these resistors were quite different from one another but both tested 8 Ohms. I thought that was odd at the time…end of story. However, Jacques brought to my attention something I had missed in the Circuit Diagrams.

These two resistors are both serving as Feedback Voltage Dividers: R12A on the Primary of Transformer T2A and R31D on the Tertiary of Transformer T3A. As such, they are wired in parallel in these two circuits, so it is not possible to get an isolated Ohms reading from them just by putting your VTVM probes either side of the resistor body. In doing so, the meter reading is biased by the transformer. You need to disconnect one end of the resistor from the circuit involved to get a pure reading of the resistor. Both of these resistors are a bear to get at, so I have decided I will simply replace both resistors outright. Do tricky work once and be done.

The other really nice bit of information from Jacques, was that he took the time to document the best current resistor equivalents that I could use to replace each of these older components. This was something unexpected, but invaluable for me. I simply do not do enough regular electronics work to be comfortable substituting modern resistors for older ones. Bumping up the wattage rating to get a resistor of correct Ohms is one thing and I have done that just fine in the past with 1/4-watt resistors. Modern ones look way too small in a piece of vintage electronics and the leads are always far too short to cover the distance between Panel Tags in a 52-Set in any event. But I am just not comfortable going to higher Ohms ratings for any given circuit. I worry too much I am going to buggar things somewhere down circuit.

Other than that, so far so good.


David

[David Dunlop]

I was able to find the two remaining resistors Jacques had mentioned to me, fairly easily. I must be getting used to tracing the components finally.

R39B is located on the rear end of the Sender Tag Panel AS, which is located on the inner right skirt of the sender chassis. R47C sits right at the end of the Microphone Jack assembly. Photos attached. The test results for both are as follows, following the same convention as my earlier posting for the first 10 resistors:



R37B, 15,000-2, 20, V5D Plate feedback Limiter, Tested 15,960 Ohms
R47C, 50,000-1/4, 20, V1J Grid Voltage Dropping, Tested 58,200 Ohms


Both of these will be replaced.


While I think of it, Sender Tag Panel AS, in the Illustrated Parts List for the 52-Set is actually, PANELS, Phenolic, 12-Tag ZA/CAN 4224.


David

[David Dunlop]

I now have a list of current suitable carbon composite resistors to replace the ones I have found so far needing such attention in the Sender. Finding ones I can actually use in restoring the Sender is shaping up to be a very big challenge, and the fact it jogs me back to the same issue I had when replacing resistors in the two receivers is not helping.

Working on any of the smaller Tag Strips, or the valve sockets, is not a problem. Even the smaller Tag Panels can be worked with, but it is the larger Tag Panels which are a problem. The tag spacings on these panels are either 2.25 inch for the smaller ones or 2.5 inch for the larger ones. When you start looking at replacement, new production, carbon composite resistors, you quickly find the sum of the lengths of the resistor bodies and the two axial leads seems to give a modern standard length of 2.38 inches. So with a lot of careful dicking about with an easily accessible Tag Panel, you can just fit a new resistor across the smaller panel, but are SOL doing so with the larger Tag Panel. Most of the resistors currently needing attention are, of course, on a large Tag Panel. I am a bit of a way from getting the capacitors sorted, but suspect I am going to run up against the very same 2.38 inch overall length limit with them.

There are a few companies out there dealing with fairly extensive NOS supplies of carbon composite resistors but none (rightly so) guarantee the specs of the components anymore, and using them for jewellery purposes seems a common theme.

About half of the resistors I am looking for are also used in the receiver so I could hunt them down for testing and reuse, but if they are not installed in Tag Panels currently, it is very likely their leads have been trimmed too short to be of use, even if solidly on specifications.

So the Sender sits on the bench while I ponder the situation.



David