Sure, Eric, here is a picture of the water level sensor. It sits above the tank and has two copper probes that extend down into the pour-over tank and once the water level gets to a certain point, they short out and should tell the microcontroller there is water.


There is a La Cimbali dealer in Des Moines. I had previously contacted them about refurbishing the machine and they were going to replace all the valves + the heating element in addition to tear down and descaling at a cost of about $1,000. I was going to have them do it until 1) I joined HB and 2) I had to take unpaid time off from work (furlough) due to the economic situation.

I can always take it to them, however, if there is a problem with the board, all they're going to do is replace the board, and I hear the board for these machines is very pricey... so if Cecil or my friend Jason (the EE) could fix the board, that would probably be much less expensive to pay one of those guys for a board repair than to purchase a new board.

I may call them Monday and see what they say about the problem.

Then the test would be whether there exists continuinty in the individual wires between the end which connects to the probe and wherever the wires connect to, i.e. are the wires themselves OK ?

Yes, wires are OK. I ran continuity tests.

Shorting the wires, while that seems like an obvious test, may NOT be the proper trigger with your machine. I would think the board is looking for a "reasonable" resistance - something other than zero.

When I first tested it, I had water in the tank and the probes down in the water and the same thing happened. I can try it again by dipping the probes in a cup of water or something. I'll do that just to double check.

I am NOT suggesting you take the machine to the Cimbali dealer. I am suggesting you become "best buds" with them as they have SURELY seen this problem before and, like all (most) machinery repair facilities, have a "gold locker" containing just the parts you MAY need.

That sounds like a good idea. I'm sure they'd be happy to sell me parts if I need them. And you're right, most repair organizations keep a cache of old parts around. I do computer work and I know I do. I'll give them a call.

Jason was suggesting that I try to measure voltage at the analog inputs of the microcontroller and see what I was getting when the water tank probe circuit was open vs. closed. It will be a little difficult to do that but I think I can manage. Based on the information I have on the microcontroller I have it narrowed down to about 8 pins. I'll have to use a magnifying glass to try to follow the traces and attempt to figure out which pin I should be checking. Maybe a continuity check could help find it. I know the pin from the tank probes goes to resistor #26 on the board -- I verified this with a continuity check last night. I should be able to check continuity from the other side of R26 to the pins on the 74HC14, and then from the info I have on the HC14, the output of that to the microcontroller and find the appropriate pin.

Just a silly question, you are not using RO or distilled water for testing are you?

-Cecil

PS I still say your controller is fine.

Just to follow myself up, the mess on C3 looks like it was caused by water at some time, should be fine for that part.

One other thing, that diagram that Eric posted says that J1 did not do what I thought it did. One way labeled Caffe and the other way labeled Cappachino... Could this jumper adjust the board for tank vs line pluming configuration instead?

-Cecil

I tried switching the jumper and no difference. Would have been nice!!

I've been taking readings off the legs of the microcontroller. Got more to do.

One thing I noticed tonight was that the tank and boiler probes have a voltage of .4 volts A/C. Initially I tried D/C and got nothing. (Fortunately the meter seems to be designed to survive this.) Why use A/C for that? That seemed odd to me.

I have to ask this again, what is your local water type. If you have RO that could be the problem.

-C

No water filtration or reverse osmosis here. Not using deionized water either -- just straight tap water (the machine has an in-tank water softener.)

OK lets be a bit more clear here, you traced the circuit and you are looking at a relay output right? I think you lost a couple of us with that 25vac reading. When that circuit you are reading is off there is 0v and infinite resistance. Right?


-C