Almost done hacking this old Gaggia

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Teus

#1: Post by Teus »

I think it's three years ago that I bought an old Gaggia. I still have no clue what exact model it is; it's probable the predecessor of the Baby Gaggia. It gives the impression of working well, yet being an obsolete piece of crap at the same time. It leaks water and steam from the showerhead and the steam valve. I didn't know a thing about espresso and had to learn everything by myself. Took forever. Kudos to the people on Freenode #coffee, especially Nebukadneza, for helping out frequently. I think I paid 150 for the grinder and 120 for the machine. The grinder is a Cunill. I got new burrs for it.

The thing is extremely quirky and there's something really strange going on with my grinder. Poor burr alignment or so, so I couldnt grind fine enough. I disassembled it and cleaned it thoroughly. Had to use a steel brush on a drill to get some things clean. Conditioned the seals with silicone spray, added one rubber ring on the steam valve attachment since there was none in place, added rubber rings to the part above the showerhead since corrosion ate away some parts. Plenty of corrosion all over. Aluminium snowflakes clogged a few of the nozzles above the showerhead. Since then I used filtered water. Took off the stupid attachment to the steam valve and lost it somewhere. I put in an adjustable overpressure valve and adjusted the maximal pressure with a pressure meter to about 8.5bar. Drilled a hole for the overflow line and added some fittings.

I Bought a few K-type thermocouples with low thermal mass. Temperature fluctuation between min and max was somewhere 20-30C. I Bought a Chinese Knockoff of an Auber PID temperature controller (YL-6SE) since hacking this thing was already expensive enough. It only samples twice per second and is overall pretty slow and not too smart, but that wasn't any surprise. Today I put together a cheap simple TRIAC dimmer to reduce the power of the heating element (1500W). After trying a few settings the PID has a fluctuation of less than 1 degree Celsius.

I ordered a bottomless portafilter that can hold a triple basket. With shipping included it cost a ludicrous 45 euro, but now I'll get to see some real espresso pornography. Right now my maximal dosing is 18 or 19, maybe 20 grams.

I really can't believe I'm getting carried away this much, nor that I got everything working as desired. I cursed this machine more than once for being crap. The final test will be evaluation of the crema with the naked portafilter.

Have some photos....
I still need to clean up the cabling.
Safety right now is a joke, but I dont have any children or pets to electrocute.












pizzaman383
Supporter ♡

#2: Post by pizzaman383 »

That's called the Gaggia Old White Coffee (OWC). There are threads on a site with coffee and geek in the name.
Curtis
LMWDP #551
“Taste every shot before adding milk!”

salsa

#3: Post by salsa »

Teus wrote:...Today I put together a cheap simple TRIAC dimmer to reduce the power of the heating element (1500W)...
Very cool, but I wonder: with the controller already handling the output, what does the TRIAC do?

Teus (original poster)

#4: Post by Teus (original poster) »

the PID controller only samples twice per second. when the boiler goes below the treshold, the controller enables the heating element for 0.5 or 1 second, it cannot switch faster. this causes the temperature to overshoot 3 degrees.

the TRIAC dimmer simply "chops" the sine wave so you get less voltage. this tunes down the power of the heating element. with a potentionmeter I can nicely adjust the power, this is way easier than buying a faster (more expensive) PID or finetuning the PID controller settings.
a simple TRIAC circuit is cheap and works well for a dumb heating element.
I'm also using a TRIAC dimmer to reduce the power of my popcorn popper for roasting