I decided to take the whole thing apart. This was one of my better decisions as you will soon see. I was expecting the machine would have been washed very rarely, but this was unfortunately too optimistic.

he apparently used the machine as a salt and pepper combo grinder ...

I started simply mapping the electrical connections (the paper and the multimeter) but like all projects it quickly expanded to become an entire rebuild.

The stainless steel boiler and the brass arm to the steam wand and 3-way solenoid. The nut connecting the steam wand is counter-threaded, meaning to loosen it you need to go clockwise. This took me far longer to realize than it should have .


Here's the inside of the boiler, absolutely coated in scale. Thankfully there appears to be little to no corrosion, which is a reported problem on these machines.
Hard water contains minerals which are soluble in water. These minerals, principally Ca(CO3)2 and to a lesser extent Mg(CO3)2 are quite soluble at lower temps but when the temperature increases in the boiler, one of the carbonate (CO3) groups breaks off, forming CaCO3 and MgCO3 which are less soluble than the original Ca(CO3)2 and Mg(CO3)2. These (the CaCO3 and MgCO3) then precipitate out of the solution and into crystals known as limescale, or more commonly scale. The large amount of scale indicates the person I bought it from had hard water, which is actually a blessing.
In soft water (tends to be slightly acidic) the two different metals in the boiler (stainless steal) and the group head (brass) of the Gaggia Classic forms a galvanic couple, which is like a battery, resulting in a quicker corroding of the anode (the boiler). Between a messy clean up and replacing the boiler, I'll take the former any day.

Heres the connection between the solenoid and the boiler, which clear signs of clogging, though it doesn't appear white like scale. Any thoughts?

The same buildup is present on the connection between the boiler and the OPV


More pics of the OPV. After this is all cleaned up, would I make adjustments to the OPV pressure with the nut on the top?

This pic really doesn't do justice to how filthy the steam wand was. This was an older model Gaggia classic with the metal steam wand (it took a TON of force to get it off) and it looked like no one ever had cleaned the inside. This was taken after I removed the resin-like substance of a decade worth of lattes. I'm planning on removing the wand entirely and replacing it with a Rancilio Silvia steam wand (it is compatible thankfully so no coupling necessary)

I can now immerse the head in some heavy duty cleaner (brass safe of course). It is a wonderfully solid feeling piece - the thermal capacity of it is great as well.

Good luck getting it back together. Should be a solid machine.

I wouldn't worry about preheating water, small boiler etc...I've always been a little skeptical of the idea that brew temp has to remain stable through an entire pull. How many chefs, for example, cook food at exactly the same temperature throughout the process.

What is worth doing is finding a routine that works. For my tastes, which are cooler brew temps, I do this by flushing several ounces of water through the group to cool it just before brewing. For warmer temps one can flush, then wait just until the boiler cycles off, etc.

PC

peacecup wrote:I've always been a little skeptical of the idea that brew temp has to remain stable through an entire pull. How many chefs, for example, cook food at exactly the same temperature throughout the process.

To be fair, nowadays few claim that absolute temperature stability is important, but everyone agrees that the repeatability of the brew temperature profile is important.

I just pulled a great shot off of the machine - the first since fixing it up. I was having an issue with weak shots that pulled in 15 seconds for a doppio, and after adjusting the grind several times (hand grinder so it took a while), I got a 25 second pull that tasted great.

Very nice Robert, good job getting it back together again