Gaggia Classic, Schematic diagrams, PID-ing

Equipment, technique, or just drinking the stuff

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Postby ben_edwards » Fri Aug 18, 2006 7:44 pm

Glad to hear you are healing Jon, and better still it hasn't put you off tinkering some more 8) (did you kill the old SSR when you shorted the circuit? or is this another project??!) I've been playing with the temperatures a bit but maybe I ned to better control some other factors too... its so hard when you are needing to grind finer due to age of beans etc. to actually know what is affecting what! I think we will need some time to find out for sure the best method! But I am impressed at the consistancy of the quality of the shots it has produced regardless of temp after some practice. I think some earlier naff shots may have been inexperience, or maybe some of those other factors... as I've had some great hotter shots too now. Since the PID I'd say 9/10 were good shots, with all the qualities people point out - the body, the taste, the crema, the flecking pattern in the crema; and most importantly I like the taste and experiance!

By the way I forgot to mention before, if anyone needs an SSR I have 2 spare, just PM me.
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Postby lukas » Sun Sep 03, 2006 9:41 pm

This thread is now 6 pages long, I just thought why not post a picture of the pid and thermocoupe. Yes, it arrived! And man, I thought it was 4 times as big as it is .. it's tiny!

See here (currently uploading). Will be fun installing it next week!
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Postby lukas » Wed Sep 06, 2006 10:13 am

Hm. I must have done something wrong. After reassembling (the PID is not yet in action, only testing places to put the thermocouple) the heating element just won't switch off. I guess it's a) a broken thermostat (unlikely) or b) me made a mistake while rewiring the thing (likely).
Well, that's the fun part of it, ain't it? :)
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Postby Captain_Crema » Wed Sep 06, 2006 1:23 pm

Have you reset the trigger temperature? It is set to 0800 degrees C by default (and the manual says that really means 80.0, but it's wrong). Set it to 0080. Also, don't use the fuzzy logic mode, it doesn't seem to work, and make sure the thermocouple is connected the right way round.
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Postby lukas » Thu Sep 07, 2006 7:48 am

Ah well, I have not yet connected the PID to the SSR to the heating elements. I just reassembled everything and somehow must have shorted the thermostat or sth like that ... perhaps I've got time at the weekend to dive deeper into it.
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Postby Captain_Crema » Thu Sep 07, 2006 8:57 am

Well, is it showing the correct temperature, then?

Also, the PID is set to trigger both the relay and the SSR output - you should turn the relay off (it will then stop clicking). It's (mostly) in the manual that is on the palmelectronics website (along with a wiring diagram for a coffee machine - handy..).
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Postby lukas » Thu Sep 07, 2006 5:10 pm

Nope, it's not, but that's because my tape didn't stand the temperatures ;). I'll try to find some time working on it on the weekend.
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Postby DavidEdge » Fri Sep 08, 2006 3:19 pm

Apologies if I missed it, but has anyone posted a description or photo of how to get the stud fixing off the end of the XMT7100 thermocouple?

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Postby lukas » Fri Sep 08, 2006 4:27 pm

Great question david, I was about to ask this as well :)
Seems a bit hard to get apart.
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Postby lukas » Fri Sep 08, 2006 4:32 pm

btw, does someone have a diagram of the electrical wiring of the classic? Of interest is especially the brew/steam-switch, because I think that's where I messed up things while reassembling the kit ... uargs.
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Postby lukas » Fri Sep 08, 2006 6:05 pm

Okay, the thermostat works I think. I put a bit of heat-conductive paste on the screw before screwing it in, but now my thermometer reads higher temperatures than before ... it switches the boiler on at about 100°C and off at about 120°C. I suspect it's somehow not well enough connected to the boiler?

The other thing is ... my boiler leaks now pretty badly, even though I didn't take it apart. Guess it was just that taking it out made the ooooold seals break. So, now I have to take it apart and replace the gaskets I think... i hope the gaskets of the new boilers will fit!
damnit.
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Postby Captain_Crema » Fri Sep 08, 2006 8:22 pm

DavidEdge wrote:Apologies if I missed it, but has anyone posted a description or photo of how to get the stud fixing off the end of the XMT7100 thermocouple?

David Edge


Piece of cake, but you have to be brave.

Note that the fixing is crimped to the braded steel shroud of the cable. Using a watchmaker's screwdriver, lever the crimps out, then carefully withdraw the cable from the stud fixing.

Sorry no pictures, but it's really simple, honest.
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Postby Captain_Crema » Fri Sep 08, 2006 8:23 pm

lukas wrote:btw, does someone have a diagram of the electrical wiring of the classic? Of interest is especially the brew/steam-switch, because I think that's where I messed up things while reassembling the kit ... uargs.


There are wiring diagrams on the link posted earlier on in the thread.
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Postby lukas » Fri Sep 08, 2006 8:36 pm

Thanks, I didn't notice that earlier. Have to wait a bit with the PID until the boiler is fixed ...
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Postby ben_edwards » Sun Sep 10, 2006 1:38 pm

lukas wrote:Okay, the thermostat works I think. I put a bit of heat-conductive paste on the screw before screwing it in, but now my thermometer reads higher temperatures than before ... it switches the boiler on at about 100°C and off at about 120°C. I suspect it's somehow not well enough connected to the boiler?

The other thing is ... my boiler leaks now pretty badly, even though I didn't take it apart. Guess it was just that taking it out made the ooooold seals break. So, now I have to take it apart and replace the gaskets I think... i hope the gaskets of the new boilers will fit!
damnit.


Lukas, those temperatures sounds about right. My thermostat has 107C 8C printed on the side, which - I believe - means that it switches on at 99C and off at 115C, perhaps your thermostat my have similar markings. I think the precise measurement is not important really, you may just set the target temp differently than others. O think though that using thermal paste the thermal contact will be much improved hence the higher readings.

I removed the thermocouple screw as Jon described, basically by uncrimping the crimp! I think I used pliers to squeeze the crmp open, but the small screwdriver idea sounds good if you have one to hand. I then soldered the end of the thermocouple to a screw that fit into the hole where the brew thermostat used to be, and helped the contact using some thermal paste. I am sure soldering directly to the boiler, or clamping it on somehopw will have similar effect. To check the pid is still seeing the real temperature I just tested the temperature of boiling water. The soldering/removal of screw etc had no effect on mine.

If possible, while you are still using your pid as a thermometer it may be useful to try and measure the temperature of the boiler, and the temperature of the outgoing water to see what sort of loss in temperature there is.

I hope you can easily repair your boiler. I would be interested to see what the inside looks like wiht all this talk of corroding aluminium!
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