Wireless Set No. 52 Canadian - Project

[David Dunlop]

Thanks for the input on wire lengths, Chis. Much appreciated.

My apologies if rumours of the death of either myself, or this project, had begun to circulate. Neither is true.

I have been sidetracked during the three sets of resistance tests I needed to complete on the 52-Set Sender. The main cause was some very odd readings I was getting. The initial assumption was a serious fault, or faults, lurking somewhere in the Sender, but as I pondered all the data; a more likely suspect for the high readings began to be my Digital Multimeter. It has performed very well whenever I needed to test a more modern, solid-state piece of electronics and never gave its reliability much thought. I began to have second thoughts when so many Sender tests started showing up where the DMM sampling rate simply would not stabilize, and would start a massive sweeping action, either in Full Auto Resistance Mode, or a narrower manual resistance range. In Auto, it invariably ended up reading at Infinity and stop working.

15 or so odd results showed up in the final data collection and I was suspicious enough to pull out my RCA VoltOhmyst VTVM (actually the recommended VTVM in the Canadian Army Test Instructions for the Wireless Set No. 19 and the 52-Set) and randomly sampled three of the odd tests. All three came back higher than I would have liked, but not even close to the ‘Infinity’ values the DMM was giving me.

So I started redoing the testing with the RCA Analog Meter for all the really odd values and from time to time rechecked a few of the tests that came back OK on the DMM. All was going well for a while and then the good test results started going off. A quick check of a couple of known resistance standards showed those results were now out and panic set in. After about a week, it dawned on me I had been watching the RCA Analog Meter warm up and was checking the Zero status of the needle in voltage mode while the meter warmed up, but had forgotten to also Zero the needle for Ohms. So I tried that and could not get it to Zero to save my Soul. I had put a brand new pair of D-Cells in the VTVM in January, so they were not on my radar, but should have been. When I finally realized they were worth a look, one tested 1.34 Volts and the other came in at 0.32 Volts. Popped a brand new set in and problem solved.

In the meantime, checking my two digital multimeters showed both were quite accurate and the RCA gave me results that were so close to correct resistance values I was a happy camper. However, my only backup analog multimeter, a cheap modern one about 15 years old, was consistently 25% off values for resistance, It’s manual claimed +/= 5% when new. So I was short a reliable analog backup.

I have now found a very nice, very accurate Simpson Model 303 VTVM, and being a give away, I am a happy camper and can now get these tests finished on the Sender.

David

[Bob Carriere]

Batteries do fail....even new from the package.

Digital is fine to a point...... when it goes South there is no fixing....

and how quick we get used to instant results........ old radios were famous for taking it time to warm up....anything with tubes need patience.....which years ago did not seem to bother us...... You are one of the few left who exudes of patience, persistence and problem solving skills with the old electronic radios....

My old tube tester instructs in bold character to allow the instrument to reach room temperature than 10 minutes for proper warm up....... and then to proceed with an item of known value before testing components.

Always enjoy reading your trials and tribulations........

Bob C

[David Dunlop]

Thanks, Bob.

This project certainly generates them.


David

[David Dunlop]

When I recently got the Simpson VTVM, the other half of the equipment ‘give away’ it came with was an older bench Frequency Counter rated to 80 MHz. I haven’t a clue if it will ever be useful in working on either the 19-Sets, or the 52-Set Project, but what the heck...it was free.

It is all solid state, probably late 60’s or 70’s in design, utilizing a probe to connect to the equipment being tested. Currently hunting for documentation to figure out how to use it. From the little reading I have done on these things, direct hookup between the counter and the item being checked would seem to be an advantage because of the ever growing amount of RF pollution these days.

Last weekends rain/snowstorm here, which finally said goodbye last night with a cm dusting of snow, halted 52-Set work. Water got into our basement with enough enthusiasm to get ahead of the sump pump. We had a 2-inch deep 9-foot diameter pool of water that just wicked onto two area rugs and a couple of floor mats before the pump evened the odds. 20 minutes of stability and the pump finally got ahead of the incoming water. Everything is about 90% dry again and back to normal, but we certainly didn’t need the excitement.

David

[James D Teel II]

Our house flooded three times while I was growing up in SW Oklahoma. I can empathize with what you're dealing. I'm glad to see you back on and I pray the damage wasn't too severe.

By the way, I appreciate all the help you've given me with my radio. Check your email for the results.

[David Dunlop]

I am happy to help whenever I can, James.

I was able to get the first set of Sender Resistance Tests reviewed today with my now nicely calibrated RCA VoltOhmyst VTVM, after letting it warm up and stabilize for half an hour.

On the first go back on 10 April 2022, 18 of the 72 tests in this set came back noticeably off specifications and/or ‘odd’. Of those 18 reviewed today, five now came back on specification and the others were noticeably lower in value, or unchanged. So roughly 30% of those 18 readings are now resolved and the rest will need to be investigated.

The Socket for Valve V1J (an ARP-3) has half of its terminals hidden behind the Microphone Transformer T2A, which forms part of the V1J Grid Circuit. For the 10 April 2022 testing, I had chosen to test the V1J Socket terminals from the top, and the probe pins felt a bit too sloppy in the holes, so this time, I decided to remove the T2A Transformer from the lower rear chassis wall of the Sender. This is easily done, as it turns out, by simply removing the two sets of hex nuts and lock washers, as shown in the attached photos. I just let it hang carefully on its leads until the tests were completed from the bottom side of the V1J Socket and then reattached the T2A Transformer to the chassis.

Now onto rechecking the suspicious results for the second test.


David

[David Dunlop]

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