As a kid I tried to learn about electronics the old fashioned way – tear something apart and try to put it back together. Unfortunately I did not have someone overseeing my explorations, and so very little was actually learned! If amateur and shortwave radio itself is an attempt to recapture something I really enjoyed when I was young, tinkering with electronics is even more so a fulfillment of something I sought as a child.
Electronics, as it applies to the radio hobby, is almost as magical as the signals these radios receive. Antennas grab signals as they course through the air, and a radio figures out what to do with them. Have you ever thought about how amazing it is we can distinguish one signal from another? Oh I know we all think about tuning and filtering and selectivity, but I find it amazing we can tune a radio at all. Maybe I am still the child in my way of thinking, but it is not as though radio signals are all lined up in a neat little row waiting to be picked off one at a time like soldiers marching in formation during ancient battles.
When one considers all of the signals bouncing around — and I mean literally thousands of signals at any one time — it is an absolute wonder we can hear anything at all. The harmonic combinations alone must be staggering, not to mention reflections and just the general noise of all those electrons vying for attention. And yet someone figured out things like oscillators, mixing stages, intermediate frequencies and superheterodynes. Amazing! And we take all of this for granted most of the time as we push a button or turn a dial — it all seems so easy.
Learning how things work does not remove the magic for me, in fact it only increases my appreciation for the part we play and the part played by this incredible Creation in which we operate according to the laws of physics. That we live in an ordered world of predictable results makes all of our radio explorations and inventions possible. And because I seem to have an insatiable curiosity about how things work, particularly old radios, I have taken the first steps toward my goal of being able to restore these marvels of history.
Recently I have acquired some equipment, both old and new, for testing parts and circuits, as well as gathering some of the multitude of little tools and accessories one needs to disassemble and reassemble equipment. I have also built an old fashioned, yet highly effective current limiting device for protecting circuits under test from overload.
The idea here is to provide protection when powering up old equipment in the event a component fails, suddenly drawing large amounts of current, such as in a short circuit. When this current limiter is functioning normally, the power is passed right through to the device under test. When the device suddenly draws a high load the 250W bulb begins to glow depending on the level of current draw. Even if the draw is extremely high, only the bulb will glow and very little current will be passed on to the device, thus protecting the other circuits, tubes, etc.
The bulb is wired so that only the hot wire is connected to the bulb creating a circuit path. The higher the current draw, the brighter the bulb, and thus an easy way to tell if something has gone wrong without damaging the radio. I still plan to use a Variactor to apply power slowly when initially testing so as not to overwhelm the old radio or piece of ancient test equipment.
The NRI Capacity Tester pictured at top is my first real restoration project. It is an eBay purchase and the unit is in excellent condition cosmetically. Almost nothing needs to be done in that department. The real work will be discovering what needs to be replaced inside. Certainly most if not all of the capacitors will need replacing. Hopefully the tubes are in good shape, and especially the “eye” tube which is used to indicate capacitor fitness under load. The unit will also test for leakage which is really important for older rigs. If the transformer is usable and the tubes work, most everything else can be replaced easily. The seller claimed the unit powered on, but if not done properly, that might have caused some parts to blow. We’ll see!
I purchased this after watching an interesting set of videos on You Tube describing the restoration and use of this same model tester. The maker of the videos was obviously very knowledgeable about the unit, and sang its praises once restored. I had just added the unit to my watchlist in eBay when I did a Google search for information and the You Tube videos came up in the search. I went back and made an offer which was accepted, and the seller shipped right away.
Once this unit is working I will then be able to use it to help with other pieces of equipment, one being a vintage Hickok Signal Generator. It is crystal-controlled, which means it can be used for very accurate testing, as well as working with harmonics. This of course will lead to further restorations, and so on, and so on.
Well at least I hope so! Along the way I hope to learn a great deal about these vintage pieces of older equipment, as well as gain experience working on boat anchors, my real goal. Once again I ask, “Is this a great hobby or what?!!” – 73, Robert