I don't think the details are pertinent so I'll just get to it. I applied too much voltage to a diode bridge which I didn't build that was intended to withstand high heat. I am trying to replace the bridge and I realized my digital soldering iron won't melt the stuff at 850 *F. I know I can just clip it but I would like to remove all that build up, if possible. What could they have used and should I re-attach my diodes with the the same? Thanks.

 

Try applying a little flux. If you don't have flux, apply a bit of new solder to get things started. Has worked for me in the past.

 

If that's an ultrasonic transducer, it may be silver solder or some other high temperature "hard" alloy.

 

Thanks. I guess I posted too soon. Using a little solder on the tip with the temp all the way up did the trick. I was kind of wondering about a high temp solder though because every other electrical connection in the thing is crimp or rivet. Thanks again. What a great first post experience

 

Those are 1N4007 diodes rated at 1000 volts. I cringe to imagine how you got too much voltage on those!

 

Especially since they are soldered onto a small DC motor!

Maybe the diodes were killed by excessive current, those DC motors can draw 10A or more under conditions like stall and startup.

 

I have some doubt that they died of over-current. They often fracture when that happens, and those look perfect from the outside.

 

Especially since they are soldered onto a small DC motor!

Of course it's a motor. What was I thinking/seeing!

 

Okay I guess more details are in order...

The circuit originally took 110V from the wall and went through some heaters (dropping the voltage) before ending up at the rectifier bridge. I took those resistances out of the circuit and use 24 V from a transformer to power the motor. I accidentally applied the wall power across the circuit for just a instance (long enough to trip the breaker) so I guess that the amperage was in fact exceeded. The diodes have all lost their forward bias. I still applied too much voltage for the given circuit though, so that is why I made that statement. I guess I should be more careful in my wording.

 

Of course it's a motor. What was I thinking/seeing!

I was wondering when you will realize that ?

 

Now it makes sense. The diodes don't fracture in the time it takes a breaker to trip on a hard fault.

Try maxing out the load rheostat on an analog power supply that doesn't have current protection and you will see diodes fracture. I love the crackle of exploding thermoplastic in the morning.