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Old January 10th, 2019, 05:16 AM   #1
Greg7683
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Lit match smell coming from the control box

Yup it tends to smell like sulfur smell in one or two of our control boxes been doing it for years but was never able to figure out where it was coming from. Any Ideas as to what parts can be emitting the smell. It has servo amps PLC modals in it as well as other stuff in the box.
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Old January 10th, 2019, 05:51 AM   #2
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Some components on circuit boards give off different smells when burning. You would have to tear down each one and look for burnt components.


You could remove items one by one, power them up on the bench under a load, and see if the smell is coming from that one. Since it is more than one panel I would look for components that are common to them.
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Old January 10th, 2019, 05:54 AM   #3
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It may not even be anything burning. A lot of times electronics give off certain smells when they warm up, and it really varies. *MOST* electronics that generate a nice bit of heat have an odor if you get close.
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Old January 10th, 2019, 06:04 AM   #4
Greg7683
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Yeah it is two boxes that I know of and it is strong enough to make my nose kinda burn when I smell it.
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Old January 10th, 2019, 06:12 AM   #5
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I've smelled that from toasted MOVs.
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Old January 10th, 2019, 06:21 AM   #6
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Whats a MOV
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Old January 10th, 2019, 06:51 AM   #7
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Metal Oxide Varistor. A common use is as a surge supressor for AC voltage.

We used to use them on induction heaters, and when they failed it was usually in spectacular fashion. Typically you'd find a big skidmark on the back panel where they were bolted down and a loose wire with the remnants of the connector attached to it, and shrapnel in the bottom of the cabinet.
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Old January 10th, 2019, 07:09 AM   #8
A_G
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Quote:
Originally Posted by sparkie View Post
It may not even be anything burning. A lot of times electronics give off certain smells when they warm up, and it really varies. *MOST* electronics that generate a nice bit of heat have an odor if you get close.
My laptop has been smelling for the past few months and I was worried at first but it's been running fine other than that. If the panel has been smelling for two years it's probably fine. You can try to isolate the device it's coming from by powering everything down/turning all the breakers off etc then slowly powering devices on, one by one (turning circuit breakers on, one by one).
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Old January 10th, 2019, 08:06 AM   #9
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A sulphur- like smell could be a selenium rectifier. It would have to be a pretty old panel, but possible.
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Old January 10th, 2019, 08:28 AM   #10
LoganB
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Always a bad day when sulfur smells are coming out of your rectifier.
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Old January 10th, 2019, 08:55 AM   #11
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Any chance that you're near a sewer or drain?

Years ago I was in a plant that was getting water in one of there panels from a leak in the roof. The fix was to punch a hole in the bottom of the cab. and run a hose to a drain. Whomever did this really didn't want the hose coming out of the drain so he pushed it down passed the trap, thus letting the sewer gas up into the control panel.
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Old January 10th, 2019, 09:51 AM   #12
Greg7683
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Any chance that you're near a sewer or drain?

Years ago I was in a plant that was getting water in one of there panels from a leak in the roof. The fix was to punch a hole in the bottom of the cab. and run a hose to a drain. Whomever did this really didn't want the hose coming out of the drain so he pushed it down passed the trap, thus letting the sewer gas up into the control panel.
Nope no drains anywhere near that area.
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Old January 10th, 2019, 12:11 PM   #13
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Always a bad day when sulfur smells are coming out of your rectifier.
I personally try and avoid venting my rectifier while inside a small office space, I find that helps save face.
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Old January 10th, 2019, 12:20 PM   #14
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A sulphur- like smell could be a selenium rectifier. It would have to be a pretty old panel, but possible.
They really do give off an eggy sulphurous smell in their way out
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Old January 10th, 2019, 05:17 PM   #15
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If there is a UPS in the panel with a lead-acid battery, that could be the battery venting hydrogen-sulfide gas. You should not have a lead-acid battery in a panel that is not ventilated, bad things can happen.

If not, a selenium rectifier would have had to have been in a 1960's vintage component, like an old linear power supply or something. When you get that smell, it meant the rectifier was failing, to where the forward voltage would be increasing, typically resulting in other parts getting fried. So if it's been going on for a while and nothing has died, that scenario is unlikely. A selenium rectifier always looked like a stack of plates, like fins on a radiator.

Last edited by jraef; January 10th, 2019 at 05:21 PM.
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