Equipment Oddities Make Repair a Challenge

By Robert Swink, Lab Manager

I’ve dealt with a lot of different types of test equipment over the years, but I’m still amazed sometimes at what lands on my bench. The only way to explain this is it’s just plain odd. As if dealing with all the sophisticated circuitry in modern test equipment isn’t tough enough, I’ve had to deal with odd modifications, strange setups, and confusing control panels.

Odd modifications

I cringe when I open up equipment and find odd modifications. Sometimes there are components missing from boards, circuit board traces that have been cut, or wires soldered to components on the board and or control knobs. Many times these modifications are not documented on the schematics that I have.

Manufacturers tell me that these are just engineering changes, but these mods make it very difficult for the service technician, especially when these changes have been applied in a sloppy way. It’s hard to tell what’s going on, and you begin to doubt what you’re really troubleshooting.

For example, I recently worked on some equipment that was blowing fuses. When I opened the box, I saw so many modifications that I was distractedaway from my basic troubleshooting approach of using your senses when troubleshooting test equipment that I just shared on my last posting! I was so focused on these modifications, that I forgot to do a smell check and missed the fact that one of the boards had a burnt component. I finally got past all the mods and did find the bad component, but it took a lot longer than if the boards had been clean.

 Strange setups

Setups can be odd, too. For example, some of the older travelling wave tube amplifiers (TWTAs) require that you load their inputs and outputs before operating the amplifier. Failure to do this can damage the TWTA.

Some equipment requires even stranger setups. One piece of equipment that I worked on needed to have the proper buttons pushed on the front panel prior to turning on the power.  The manual stated that, should the proper buttons not be pushed in and or pushed out, the equipment will fail and may even enter a complete inoperative state. How odd is that?

Confusing control panels

Often, a manual will warn you not to turn off a piece of equipment until the internal calibration is complete.  They never tell you what happens if the power goes out or if the power gets turned off inadvertently. When I see that kind of instruction I wonder if anyone has actually done this and what happened when they did? If that’s you, what happened?

Some control panels are so unusual that they’re almost impossible to use, and the manuals are often not much help. I’ve had customers call me and say, “I’ve read the manual several times, and I still can’t figure out how to do it.”

Other panels are so bizarre that I find myself wasting hours just figuring out how to use it, let alone determining if the equipment works. I wonder what the engineers were thinking when they designed this unusual interface? Don’t they realize that the harder something is to use, the less inclined people will be to use it?

 Well, that’s my tale of woe. Now it’s your turn, what equipment oddities have you come across? Share your experiences here so we can all learn.

At Axiom Test Equipment, our job is to ensure that you get the most out of your test equipment. If you have any questions about test equipment repair or preventive maintenance, please feel free to contact us at or 760.806.6600 and ask for Robert our lab manager.


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