Maker Pro
Maker Pro

While trying to fix a pinball machine, I had a big scare

edhalsim

Nov 8, 2017
3
Joined
Nov 8, 2017
Messages
3
All the components in the machine run off AC power, in this particular case 50V. I was trying to measure AC voltage using my multimeter. Holding one probe in each hand I connected two points and the thing nearly blew up on me; it started sparking with even a little smoke before I could get the machine powered off.

While I feel OK, I'm wondering if any of the current flowed through my arms across my chest since I was holding one lead in each hand, or was the path of least resistance through the multimeter itself? Am I OK or should I be worried?
What's a bit odd is the house fuse didn't blow and my multimeter seems undamaged (though I can't say the same for the machine).

What other precautions can I take in the future? I was wearing thick soled leather boots at the time, but I don't think that would help me in this circumstance. Maybe getting leads with grippers on them so I don't have to use one arm?

Thanks.
 

dorke

Jun 20, 2015
2,342
Joined
Jun 20, 2015
Messages
2,342
Welcome to EP.

If the current would have flown trough you ,you would have felt it.
The leads are insulated and would stand 230VAC easily.
I guess you are mentally shocked ,but physically fine.

I also guess that while probing ,you accidentally shorted something in the machine.

Why do you think that the fuse on the multi-meter should blow on ACV?
Is the multi-meter a DMM or a needle type one?
Does it still work on DCV,ACV,Ohm ?
What is your experience with electricity/electronics?
Please post photos of your meter it's probes and their tips ,and the fault/smoked parts in the equipment
 

edhalsim

Nov 8, 2017
3
Joined
Nov 8, 2017
Messages
3
It's US 120V AC. Coming out of the transformer it's 50V AC.
It's a DMM. Measuring both AC and DC voltage still works fine. The tips seem fine.
IMG_3363.JPG

Here's the area (bottom part on the right side of the transformer) where the small amount of smoke was coming from. I can't see exactly where, or what possible damage was done.
IMG_3365.JPG

I have some experience with electronics, but I'm no expert obviously. I can't figure out what happened. I didn't think I could fry a circuit if the DMM is on AC voltage, which it was because I had just measured a different connection right before and it read 50V.
 

dorke

Jun 20, 2015
2,342
Joined
Jun 20, 2015
Messages
2,342
Can't see anything wrong.
This machine looks old,very old,40's-50's,earlier?

The insulation needs to be inspected visualy.
Could be you pushed something with a probe and accidentally shorted something.
Check the solder as well.
 

edhalsim

Nov 8, 2017
3
Joined
Nov 8, 2017
Messages
3
Yes. 1962 to be exact. All I can figure is since my meter leads are so long maybe I shorted something with the lead itself, which would be good as then there's no way the electricity went through me thank goodness. Next time I'll try using electrical tape or an alligator clip to attach the ground lead, then touch the other lead with only one hand.

I'll check the insulation and solder joints as best I can.
 
Top