worst test equipment fail? - Page 1
Forum section: electronics / general

author: CopperCone
author_rank: Super Contributor
timestamp: September 08, 2017, 12:20:07 am
content: Mine is leaving a function generator on the roof of a car. I drove down a big hill and the thing must have tumbled down like 100 feet of steep incline. An HP3310B. The transformer is rivited to a back plate, and it got loose, and the cards which are inserted into card slots broke the edges of the card slots. I just redid the transformer and realigned everything, but for some reason the rails are being pulled low. The g-forcres must have been massive on it, it was airborne for half of its fall. It went all the way into the bushes across the street, good thing there was no car driving by or it would have probably gone through the side window of the car and hit the driver!I think that if there was two more screws and 1 bracket in the unit, it would have survived with only a loose transformer. I have no idea how an electrical fault came about because of the fall though.. bond wire in a transistor perhaps.

author: eugenenine
author_rank: Frequent Contributor
timestamp: September 08, 2017, 01:01:43 am
content: Mine was leaving my tool bag in the truck and my tektronix 212. It was stolen. I used to see them every now and then on ebay but haven't seen one in a long time, I still intend to buy a replacement should I ever find it again.

author: Gregg
author_rank: Super Contributor
timestamp: September 08, 2017, 04:51:48 am
content: A long time ago I had a digital multimeter blow up on me. I was visiting a friend with a machine shop and his overhead hoist had stopped working. It was an old school type with two ropes hanging form a bell crank switch; one rope for up and the other for down; spring loaded center off. He asked me if I would take a look at it and I borrowed his Radio Shack Micronta 22-198U meter. The shop power was 480 volt 3 phase that often ran 500 volts. Even back then I was fairly cautious and tried the meter on a 120 volt outlet to make sure it worked before testing anything on higher voltage. I did notice that the dial went to 2000 but the fine print said 1000VDC or 500VAC and I should have stopped right there. I turned off the power and removed the switch cover then turned the power back on. I used a wooden ladder and made sure I wasn't grounded and held the two probes on switch terminals with one hand and pulled a rope with the other.It let out much more than the smoke, it let out the fireworks. The probe tips vaporized into the handles and later I took apart the meter to find most of the circuit board traces vaporized. The meter case held and I somehow escaped injury; I did have a plastic face shield on which may have saved eye damage. The short circuit blew 20 amp fuses in the disconnect for the hoist, 150 amp fuses in a sub panel and 250 amp fuses in the main disconnect for his shop. I learned a valuable lesson that I'll never forget. The cost of that lesson could have been much greater. Enclosed is a picture of the type of meter.

author: Ampera
author_rank: Super Contributor
timestamp: September 08, 2017, 08:40:37 am
content: In a fit of stupidity using a multimeter to measure a POTS line inside my house. The meter was fine, but it was a VoIP system with a box that generated all the POTS stuff in the basement. I managed to break every single POTS connection in that box except for the RJ test jack (for hooking up a phone just to test the box) which was eventually jury rigged into the rest of the house by means of a long phone cable.

author: noidea
author_rank: Unknown
timestamp: September 08, 2017, 01:09:46 pm
content: Quote from: Gregg on September 08, 2017, 04:51:48 amSounds like the meter was on something other than volts to create that much havoc.

author: schmitt trigger
author_rank: Super Contributor
timestamp: September 08, 2017, 01:20:06 pm
content: Gregg;you are one lucky individual. And I'm pretty sure that is an understatement!In a factory I worked for many moons ago. a similar accident happened.The poor guy was killed not by the shock, but by the fall from the stairs. He was startled by the loud bang and lost its footing.On his way down his neck hit a machine's metal bracket, severing his spinal cord.I'm glad that I did not personally witness the gruesome scene.

author: Gregg
author_rank: Super Contributor
timestamp: September 08, 2017, 05:58:58 pm
content: I think it may have been an inductive spike since it happened on the motor winding side of the switch as I turned it on. The spike was enough to start an arc within the meter and it cascaded into a major short. It was in a machine shop with lots of metal dust floating about that may have found its way into the meter landing on the circuit board making a shorter path for an arc to start.The other possibility is that the rotary switch may have been bumped as I climbed the ladder.No more cheap meters for voltages over 50V.

author: David Hess
author_rank: Super Contributor
timestamp: September 08, 2017, 08:02:36 pm
content: Quote from: noidea on September 08, 2017, 01:09:46 pmI suspect this is what happened. A couple of my old bench multimeters just like that Radio Shack Micronta use the same terminals for amps and volts so turning the function switch the wrong way while connected to a voltage source can be bad. One of my meters came to me with the 2 amp contacts in the cam switch welded together. At some point multimeter designers figured out that the current terminal should be segregated for safety.Worst test equipment fail? Hmm ...I watched the ground lead of an oscilloscope probe turn white hot and melt when it accidentally touched the wrong point. Luckily only the ground lead was destroyed.When I was like 8 years old, I took my father's analog volts-ohm meter and used it to measure the wall socket voltage. It was 120 volts AC just like it was suppose to be. Then I measured the current ...I left the first multimeter that I bought with my own money, a Beckman TECH 310, on the dash of my car and the sun turned the LCD black. I regret now not getting a replacement LCD from Beckman since I would still be using it.