Breadboarding.The noun and verb "breadboard" go back to the earliest days of radio when many things were different. One thing was that most households baked their own bread. It was baked in loaves which had to be cut with a large sharp knife. To avoid cutting up the tops of tables and counters the bread was placed on a wooden board for cutting. These bread cutting boards became the platform for building radio receivers and transmitters. We would call it primitive today, small nails were driven into the board and wires wrapped around them. I don't know if they were soldered or not. I may be old but not that old. Anyway as years passed and construction techniques improved the style of building in which all components were visible and accessible on top of the construction base took on the name breadboarding.
What method of breadboarding should you use? That depends on what you have.
- You could do it the old fashioned way and mount tube sockets on standoffs, so you could get to the terminal lugs, and drive nails into a piece of wood. Hardwood would hold the small nails better than plywood. I can't vouch for the quality of the electrical connections you would get with this method.
- The breadboard shown in the photograph was made by the DeVry Technical Institute back in the sixties. It, the institute, has been taken over and renamed several times since then. This breadboard has been modified for integrated circuits and then partially unmodified so I could use it with vacuum tubes again. The edge connector is for testing the modules that plug into my audio preamplifier. But that's another story. If you don't have one of these the chances are slim you could ever buy one even on eBay. Anyone who had one and lost interest in using it either threw it away or gave it away. Someone like me who still has a use for it wouldn't sell it for any amount of money; well, maybe a million dollars. It comfortably holds two tubes although you can get 4 miniature tubes on it.
The white blocks are called Modular Connectors. They can be placed anywhere on the red panel. They have a spring bronze clip inside which grips and holds wires which are inserted into one of the 5 holes in the connector. All 5 holes are electrically connected together.
- The idea for the "Practical Breadboard for Vacuum Tube Circuits" came to me as I was preparing these pages for uploading. It occurred to me that two of those IC breadboarding sockets (which are available from many sources) could be placed parallel to each other with tube sockets mounted upside down between them. The chassis would have to be deep enough to allow the tubes to be plugged in underneath. Wires could be soldered to the tube socket terminals to run over to the breadboarding sockets. I have constructed such a device and you can see how to duplicate it by clicking here.
After using this breadboard for several months I have found that it is not as practical as I had first thought. For one thing it is hard to get a good ground. But the main problem is that the IC socket is just too dense for tube circuits. The parts are so large that you can only use about 10% of the socket holes. The other main problem is stray capacitance. Each contact point has about 20 pf of capacitance to chassis and about the same to the adjacent contact. That's not a whole lot in low impedance transistor and IC circuits but it's a lot for tubes. It's enough to totally de-tune an IF transformer or throw an oscillator way off frequency.
- The vacuum tube electronics labs at the University of Florida used a bunch of terminal strips and tube sockets mounted on top of an aluminum chassis. Circuits were built by soldering components in place. Don't wrap the wires around just stick them through the eyes, bend the wire 90 degrees and tack it to the terminal with a small amount of solder. As in the method above the tube sockets would be mounted upside down.
If you would rather build smaller you can reconstruct the not so practical breadboard to make it into a terminal strip board.
Remember there is no law which says that you have to do exactly what I did. Being creative is a lot of the fun of building things. Construct what ever you believe will be most useful to you. In the final analysis YOU are the only one who has to be pleased with the result.
Method 1 is clunky and seems unreliable. Method 2 is unlikely unless you just happen to have a DeVry breadboard. Method 3 seems better than it really is. Method 4 may appear to be slow and arduous especially for those inexperienced in soldering but it doesn't take much experience before it gets easy and it doesn't take that much longer than solderless breadboarding systems.
NeatnessIn 33 years of teaching electronics I must have tried every kind of breadboard there is. If I had a nickel for every time I said or wrote "wire your circuit neatly" I would be pretty well off. I am forced to the inevitable conclusion that the neatness of a circuit is a function of the person not the breadboard. If you are a neat freak your circuits will look like they came out of a Hewlett Packard or Tektronics factory. If you are messy your circuits will look like an explosion in a spaghetti factory. There is nothing I can say and definitely nothing I can do to change that.
Does it have to be breadboarded?Not actually. I construct each circuit, play with it for a few days, take pictures and write it up for this web site and then take it apart. You may not want to do this. It's only natural to be proud of something you have built especially if it works well. I know this is so because I feel it myself. As I write this I have a three tube superhet radio on the breadboard which I feel reluctant to disassemble. It works as well as any all American 5 ever worked and at night I can hear stations from all over the eastern half of the United States. But I need the breadboard for the next project so I have to.
You, on the other hand, may want to build a tube radio like this and keep it. Fine. Build it on a chassis which is not too small and not too large. Fix it up so it looks nice and show it off to your friends. You might even want to put it in a transparent plastic case so the tubes and wiring under the chassis are visible. You would want to include a power supply to run it so it would be completely self contained. For permanent construction of tube circuits terminal strips are the only way to go. Wrap the wires around the lugs and crimp them tight to make a mechanically secure connection before you solder. How ever you decide to build your circuits, have fun.
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This site begun March 14, 2001
This page last updated September 16, 2002