EEVblog #1152 - 240V-120V=Magic Smoke

[floobydust]

I was a kid, figured it out while soldering a neon lamp in a some old gear.
It flashed every time I toggled the trigger 

The solenoid-style transformer has high leakage inductance as well, to make it worse.

I told my mechanic buddy to never use a soldering gun on cars and trucks, it could damage the electronics. It's pretty much the only place you need so much heat to solder.

[Dundarave]

I was a kid, figured it out while soldering a neon lamp in a some old gear.
It flashed every time I toggled the trigger

Thanks.  I can certainly understand how the electromagnetic pulse would flash a nearby neon, and I’m sure I’ve had the same thing happen to me back in the day, but I didn’t understand how a spark could actually be generated at the tip from back EMF, especially when my experience indicated otherwise.

But between the large e-mag pulse, and Ian.M’s explanation, I can see how today’s sensitive chips wouldn’t likely stand a chance.

Not that I was ever likely to use a Weller gun again for my electronics work, lol.

[mcovington]

I discovered that my old Weller EC2000 soldering station likewise had no fuse upstream from the transformer primary, so I opened it up to add one... and found that it had been built with live and neutral interchanged.  The published diagram is correct and what I actually found obviously has them backward.  Neutral was connected to the switch.

So now I have even less confidence in Weller than I did after watching the videos!

(Disclaimer: It is conceivable the swap was done by someone repairing it later.  In any case, I have replaced the power cord.)

[floobydust]

your blog adding primary fuse, nice pics 

I don't see a primary fuse in the Weller EC2000 manual, only the secondary 2A 24VAC circuit breaker EC212 which is useless. It could only deal with a shorted cable/connector to the handle - but does that even happen? It's there only to meet antique UL (soldering iron) standard UL499.
I'd guess the EC2000 uses the Tyco power transformer that may be UL/CSA Class II rated.

[noJunk]

That's nothing.
Around year 1995-2000 most industrial\home equipment had the 120/240 switch nearby the POWER ON\OFF.
The 120/240 switch on 600Watt ++ would also trigger the sound and remove a certain quantity of O2 in the adjacent room.