Nuts and Volts - October 2015

popular and their cost was quite reasonable. Today, like I mentioned, the prices have sky-rocketed, probably from lack of sales. As an interesting side note to this, about 10 years ago I had a design project that needed a high powered resistive substitution box. I found one for sale that was somewhat beat up but in working condition. It covered six decades in one ohm steps with a tolerance of

1%, and was rated at 250 watts on any range. I haggled and got it for $75. A month or so ago, I happened to see a new one advertised for almost $2,000 (and I thought I overpaid at $75!).

Next on the list should be a frequency counter. Actually, a step up from this would be a universal counter. This is a traditional frequency counter but also a period counter (reciprocal of frequency). Plus, there are other frequency related functions that extend its usefulness.

Here is a branch-off point, depending on where your primary interests lie. I think an RF generator — even a low grade one — would be an asset no matter which way you go from here. Of course, I have already mentioned the ultimate piece of equipment (the oscilloscope) which I consider to be mandatory. If I was only allowed to own one piece of TE, it would be a good scope. I consider this as necessary as my right hand.

From this point on, the equipment needed will be determined by the direction you desire to go: radio frequency, logic circuitry, digital devices, robotics, and the list goes on and on. Each discipline will have its own specialized requirements for the TE needed.

As we acquire more skills and get deeper into any specific area of electronics, the TE will also follow suit and probably get more expensive. In one’s career span, the birth of new technologies will spawn a need for specialized TE that eventually will become useless many years later when that technology is superceded by even newer technology (analog TV and CRTs knocked out by digital TV and flat screens, for example). The few essential pieces of TE I have mentioned here will probably be around for a long time, however, as they basically measure the electrical properties of the science of electronics, and that is law.

Although hand tools are not TE, they are an integral part of the test bench, so I guess I should touch upon this subject. There are a myriad of tools out there for old and new technologies, with additional ones developed all the time. As to surface-mount, the tweezer style test probes are great, as are the tweezer soldering pencils. Beyond that, everyone has their own favorite gadgets to get the job done easier — even using tools that have no bearing for SMD.

I use a set of old aluminum spring-loaded heatsink clips to hold many of these devices in position for soldering. In more conventional circuitry and through hole, I generally only have a half dozen tools on the bench: a pair of 3” needle nose pliers; a quality flush cutter; a good pair of wire strippers; a few dental picks;

and, last but not least, a good surgical hemostat. I use a fine-tip 35 watt solder iron for just about everything and a bulb type solder sucker from RadioShack, which is the most efficient type of sucker I have ever used (and it was dirt cheap).

In closing out this particular discussion, I have to say that the new “green” solder cannot even come close to the good old Kester 37/63, which just flows and grabs so much better. A good supply of random length clip leads and a few cables terminated in various connectors (BNC, SMA, F, etc.) are also mandatory items. These items will just naturally accumulate as time goes by.

Purchasing Commercial Test Equipment

When it comes to TE, there is just no substitute for quality brand name equipment, and there are dozens of top manufacturers out there. The only piece of TE I would recommend buying as new would be a moderate quality handheld DMM. All other top-of-the-line TE is just way too expensive and out of reach for most of us. So, that leaves us with buying used equipment; the go-to place here is eBay. There are various other websites on the Internet that handle used TE, so don’t neglect those. Also, if you are fortunate to live near periodic government auction sales, some incredible bargains can be had — sometimes as low as $1 per pound if buying by the pallet. eBay does seem to have a corner on the market as to TE sales, so I will dwell mainly on purchases through them. Before I get into specific equipment, I will walk you through a few general guidelines for buying.

First thing I would recommend you do is to not buy any equipment that is newer than vintage 1985. This may sound strange to you, but there are good reasons not to. From the late ‘60s through the mid ‘80s, there were big design changes in transitioning from vacuum tube to solid-state equipment which rapidly improved over these years. For sure, the ‘70s and ‘80s saw some marvelous TE equipment produced by the big name manufacturers, and a lot of it can still compete with newer equipment.

Then, enter the digital age from the late ‘80s and onward. Older technology was now being replaced with more up-to-date digital designs. Knobs and switches were being replaced by buttons and membrane switch pads. Features and accuracies were scaling upward at an accelerated rate. This was all fine and good — to a point — but had a lot of drawbacks for the home laboratory style of electronics.

Along with all the improvements going sky high, so were the prices. The cost alone for a lot of this TE even on the used market is enough to drive you away. Also, the operation of all this equipment was becoming more complex due to the multitude of features now included. If you do end up purchasing a lot of the newer TE, you will probably end up paying for a lot of features you will never use and/or never understand their use to begin with.