I posted on this at CG, but got few responses. https://www.coffeegeek.com/forums/espre ... nes/293071

Chris helped me test some things and in so doing, I discovered the problem. Have a look at this:





Now the question is, what to do next? The machine powers on and will pump water through the group head if I push a button on the panel. However, it does not heat and there is no power to the heater or pstat. I wonder if the power relay component of the board if damaged or another part of the board. I can get a new control board, but worry that another component may have caused this. Is that possible?

Thanks for any advice you can offer.

And a follow up question: how do I remove the control box from the front of the machine?

I can't help you specifically with the Expobar, but yes, I would say that evidence of a burn like that indicates an unexpectedly large current flow, and it's likely that just dropping another control board in will simply toast the new board as well.

I would suggest that there's been a short-circuit somewhere in the path, either due to problematic wiring (less likely), or failure of a major component (more likely), causing it to short.

I don't know whether you've seen a schematic for your machine, I think most consumer HXs are pretty standard in how they're designed. If you ignore the extra temperature management bits and brew boiler element of the brewtus, for which there's a schematic at:

The brewtus compendium

Then I think you have a reasonable generic wiring diagram for an HX

The control board relay drives:

1. The Heater (via the pressurestat and over-temp protection thermostat)
2. The Pump
3. The autofill solenoid
4. The steam boiler neon

I'd be looking to apply general electrical fault-finding principles to check that each of these components is not the culprit. First step would be to disconnect the wiring from each one at a time, and check for short-circuit across the terminals using an resistance meter. For the pressurestat, you'd expect a short across the common and the other wired connection, with no pressure applied from the cold boiler. The pressurestat overall state is harder to check because it needs pressure to switch it and you'll only get that with heat in the boiler.

I'd also be looking for further evidence of burned wiring or connectors throughout these areas of the circuit that might localise the fault.

Given that the pump still works from the brew switch, it would seem that the pump itself is OK.

Whilst it's possible to do all this yourself, it very much depends on your ability, and how far you're prepared to go with it. If you've been dealing with Chris, then I would continue to do so, as it seems like this is your best (and safest) bet to getting it resolved.

Jon

[Disclaimer: Advice offered in good faith. I will not be held responsible for loss or damage caused by any of the above]

Woz wrote:And a follow up question: how do I remove the control box from the front of the machine?

There should be two hex standoffs on the back, one on each side. Disconnect all the wiring, unscrew the standoffs and the control board will come out the front.

Thanks Jon, I have been through the rest of the components fairly closely already and have not seen any wiring anomolies. I tested resistance on the heater and it is fine. I'll test the pstat and solenoid later.

old442 wrote:There should be two hex standoffs on the back, one on each side. Disconnect all the wiring, unscrew the standoffs and the control board will come out the front.

Thanks, I didn't think those were actually it!

Do these control boards have a built-in relay to handle the heating element amperage passing through? Does a relay failure produce overheating that could give the charring from the picture?
Just a guess.

I'm just guessing here cause I'm not familiar with the Expobar either BUT the item you are referring to as the "control board" is simply(?) a series of membrane switches. The real action takes place in the Gicar controller to which that wiring harness from the "control board" goes to.

Certainly I think the Brewtus wiring diagram that Jon referred to is better than nutin but I would give WLL (WholeLatteLove) a call and see just how much "love" they have available in sending you an electrical wiring diagram for your machine. Given the fact that I have a wiring diagram for my $500 Sears refrigerator, I don't think its too much to ask that you get a wiring diagram for your $1000 espresso machine. Seriously, good luck.

A couple thoughts I have on this are:

1) I wonder if that connector has gotten wet (it looks like it may have). If it has then the terminals inside could/would begin to corrode, or conduct between the terminals, and will result in electrical resistance which, in turn, creates heat and over time would result in a burn like that.

2) If you want to test the pressurestat operation by creating pressure in the boiler but don't have the ability to heat the boiler this works well and will put enough pressure in the boiler to activiate the pstat. However, I would highly doubt that the pstat would cause this type of thing because it is simply a switch and not a resistive load on the circuit. Also, I believe the pstat would be a "normally closed" switch. This means it would be in the "on" position without pressure in the boiler, and adding pressure would turn it "off."

erics wrote:I'm just guessing here cause I'm not familar with the Expobar either BUT the item you are referring to as the "control board" is simply(?) a series of membrane switches. The real action takes place in the Gicar controller to which that wiring harness from the "control board" goes to.

Certainly I think the Brewtus wiring diagram that Jon referred to is better than nutin but I would give WLL (WholeLatteLove) a call and see just how much "love" they have available in sending you an electrical wiring diagram for your machine. Given the fact that I have a wiring diagram for my $500 Sears refrigerator, I don't think its too much to ask that you get a wiring diagram for your $1000 espresso machine. Seriously, good luck.

The main board and the front panel switches are housed together in a control box at the front of the machine. That wiring harness pictured is the main connector. There are a couple of smaller ones too.