I did a full descale on my Giotto Classic. I overfilled the boiler, let it sit for about 8 hours, drained it, refilled w/ fresh water, drained it.. Then ran about 2 tanks full of water through the hx and boiler. As I was nearing the bottom of the 2nd tank thinking I was almost finished.... I hear a 'POP' (like the sound you can make your lips make by putting your lips in your mouth).. Then immediately I smell something burning (smells like fireworks).. I immediately turned it off and unplugged.. I figured I would easily be able to tell where the burning was coming from since I had both side panels off, but I couldn't find it anywhere.

Can someone please help? Has anyone had this problem before? Is it the pressurestat?

I don't know if this matters, but it happened right after I drained about 8 oz of water through the hot water arm, while the pump was running to refill the boiler.

I appreciate any input.

Thanks Jim, I guess if I have no idea how to check the ohms on the heater, I should probably take it in somewhere to have it checked, right? Or is it a simple procedure? What part do you think burned/shorted out? thx

Thanks Jim. Regarding that thermal fuse connected to the boiler, does it have 2 wires connected to it with a red dot/button in between? That seems to be the area where the smell is coming from, but not certain.

The red button didn't pop out. Actually the machine still seemed to be working (finished refilling boiler) after the pop and burning smell. So if the problem is what you think it is, what type of repair bills am I looking at? Thanks so much for your help.

I didn't mean it was really working...not sure.. but the power light was still on after the pop and smell.. But I turned it off/unplugged it immediately to prevent further possible damage.

A.D., with Jim staying up until the wee hours of the morning to help you, the least you could have done is stay up with him!

I don't know nearly as much about espresso machines as Jim does, but I do know a bit about electronics and the loud pop you heard suggests that the failed device is something with sufficient mass to make a loud pop when it shorts. The heating element is the #1 guess, and Jim has already told you how to check that.

You can buy for as little as $10-$15 a digital multimeter, or borrow one from a neighbour. One of its functions will be for testing resistance, and will be indicated on the function selector switch with the sign for "ohm"... it's kind of an arch with feet... look it up on the internet.

UNPLUG YOUR MACHINE BEFORE TESTING

With the meter turned on, if you touch the two probes together, the meter will show 0 ohms (a "short", no resistance). If you then do what Jim suggested - remove the wires going to your boiler's heater, and hold a probe against each of the two connectors on the boiler (doesn't matter which is which) then the meter will give you a basic report on it's health. 1. If it shows some resistance - Jim says it should show about 10-15 ohms - then it's probably OK, you have to look elsewhere. 2. If it shows 0 ohms, just like when you held the two probes together, then the element is shorted out and you've found at least part of your problem. 3. If it shows the same as it does when the probes aren't contacting anything, then it has infinite resistance and has blown itself apart. Based on your "pop" description, the bets would be on #3.

If the element tests OK, then check the thermal fuse the same way, making sure to remove the wires first. This time, you WANT to see #2, 0 ohms, a short, showing that electricity can pass right through it.

You can work through parts of your machine like this, checking the path for the electrical energy all the way from the plug, and possibly find what's wrong yourself. Then, if you don't want to make the repair yourself, you'll at least have a leg up when you take it to the repair place.

Good luck.