Help with LGB jumbo… Funny smell

stevedenver

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I’ll try and keep this short I bought a second jumbo for a friend. I’m giving him an LGB set. The jumbo was off eBay and I hooked it up to track to test all the functions. It’s fine except the meters don’t work.

And, I also hooked up my own jumbo to the same test track to compare functions. I hooked up track leads from my jumbo.

Thus,
There were 2 units hooked up to the test track, but only one plugged into the mains at any given time.

. I did unplug eBay jumbo but left the track terminals attached to my jumbo .

long story short I noticed that in One Direction, the test loco did not go to full speed . For about 2-3 seconds. Then i raised the throttle, and, it went to full speed.

apparently I was back feeding jumbo number one and I began to smell something I had never smelled before!

This was a very short period maybe two or three seconds of a full 10 amp load. Yikes.

Having disconnected the ebay jumbo entirely, as it seems to work fine, sans meters.

On my jumbo, the one that emitted the smell, and now the only one hooked to track, Everything seems to be working fine. I left my jumbo plugged in for about 20 minutes to observe smoke, smells, etc. seems ok.
There’s no remaining smell and I imagine I fried some sort of insulation, nothing anywhere is discolored, including the VU meters. but I don’t know. I know there are those of you out there that can advise me

Having never done this before, it didn’t occur to me that the voltage would backfeed through the track clamps.

I assume i fried some coating or insulation, with the smell.

What did i do, and how bad is it, potentially. Did i ruin my old jumbo?
Again, its working fine, but that smell was freaky.

No need to tell me im a numpty,i know it, just wasnt thinking.
 
If you fried anything there would probably be a bit of visible smoke too. Insulation can take fair bit of punishment, but its wise to check its not started to shrink back from any joints. It may have been the motor windings, which would be more difficult to check
 
Back-feeding a controller with lower voltage has the ability to up-feed the power, thus the one not plugged in would be trying to up the voltage back to mains likely through some bits tgat may not like a high voltage wrong way. Some numpties have back-fed transformers wrong way with mains power that can multiply mains power many times. Moral of all this, if you have 2 transformers and controllers on one track ensure each section separated by in off switches preferably like ‘cab control’ with at worst just one wire being common. Though my preference is for all sections to be 2 pole so no controllers are connected.
 
Possibly almost melted the lacquer insulation on the transformer windings, but if it was for a short time period, you might be okay.

If it's still working after a week, you have got away with it

You should never connect 2 transformers to the same output, or the mains, as back feeding is very likely....
 
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