Bezzera BZ02 automatic and Pasquini Livia 90 - issue with membrane switch and programming

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
Jed

#1: Post by Jed »

I own a Pasquini Livia 90 semi-auto and a couple of weeks ago purchased a Bezzera BZ02 automatic made in 2007 to give to my parents as a gift. The Ebay seller claimed the machine was working flawlessly, and it is in really nice physical condition, but it came to me with a couple of problems that I have been working to diagnose. The problems may have been caused in shipping as the machine was not packed as well as it should have been, nor was the boiler drained. I think water leaked from the vacuum breaker valve as the machine was wet all over when it arrived. I dried it inside and out and let it dry for three more days before turning it on.
(In fairness to the seller, they have offered to make things right, which is much appreciated.)

The Bezzera is operating as expected except for issues related to the membrane switch / keypad and the GICAR controller:

1) The Single Shot button does not work. The led above the button is fine (flashes on turn on and if there is no ground connection with the water supply) but there is no response from the button under any conditions. I pulled the wiring harness and measured resistance between all the buttons and the wiring ground. I could see changes in resistance for the Double Shot and Program buttons show up at various pins on the wiring harness when the buttons were pressed but there was no change in resistance seen when pressing the Single Short button across any of the pins on the harness.

-->I suspect the Single Shot button has failed open but would love to know if I am overlooking something about how these machines work.

2) The Double Shot button can be used to start and stop a shot if pressed twice but will not automatically stop a shot if only pressed once (it will instead just run continuously and after a period of time the led above the button will start to flash).

3) The Program button can start and stop a shot as expected. The machine will enter Programming Mode but a shot cannot be programmed for the Double Shot button (or the Single Shot button since it is unresponsive). The machine acts like a shot has been programmed but upon trying the Double Shot button after programming it just runs continuously.

-->I suspect there is something wrong with the GICAR board (a 30uZ). I *think* we can rule out a number of potential issues because the machine is mostly operating as expected: power is fine, relays will close...but not reopen...so that tells me I am looking for the portion of the circuit that is responsible for controlling the re-opening of the relays, not the relays themselves...maybe.

---->I measured the resistance of the relays. The coils show the expected value from the data sheet. The switching side of the relays was a little more confusing and I'm not sure that I know enough about the circuit to know what to expect.

---->On each of the double pole relays, one pole showed resistance (around 1k as I recall) and one pole showed no connection. I would think that both should show no connection across either pole when they aren't energized.

---->On the single pole relay (which controls the heater) I measure resistance rather than no connection.

---->These measurements weren't exactly what I was expecting so I'm wondering if someone can confirm if this is normal? Are the relays in fact the problem rather than something else in the circuit? If it's the relay's I can change those out myself. If it is on the controller side I'll send it off to Boyt Enterprises and move on with life (I'm not set up to repair SMD and microcontrollers).[/list]

Thanks for any help you all can provide!

User avatar
hankbates

#2: Post by hankbates »

The problem could also be in the gicar flow measurement device, but usually it is in the gicar control box or the ribbon cable itself.
Pat Boyt did a great job fixing one of these boxes for me when I had a Livia 90 auto.
As you have probably seen, the simpler control box and now flow meter on the semi auto version is much less prone to issues.
I am currently looking for a semi auto setup (box and front panel) to convert the nearly new, but purchased by original owner in 2004 Livia 90 which I just purchased for my son in law, just for insurance....

Jed (original poster)

#3: Post by Jed (original poster) »

Thanks, Hank.

I didn't think to try and test the ribbon cable itself. That's a good idea.

I had ruled out the flow meter because I figured that if it wasn't working it would register 0 pulses and then the Double Shot button would basically stop working rather than run forever. That logic may not be right but that was my thinking.

Jed (original poster)

#4: Post by Jed (original poster) »

Hank, as usual you are a gentleman and a scholar.

The ribbon cable had a bad connection. That was a pain in the neck to fix. Upon that fix the buttons worked but the programmer still wasn't working so I moved on to the flow sensor... which was installed backwards from how the arrows on the housing indicate. Seemed odd. I pulled it apart. It was clean as a whistle. I reinstalled it right way round and now the programming works!

I pulled a couple shots and everything appeared to be working fine. But when I went to backflush at the end the pressure didn't release from the three way valve into the drip tray as it should.

The solenoid is measuring ~440 ohms across the coil and there is voltage present. Pulling the valve apart it also looks really clean and the spring appears strong.

The part that is making me scratch my head is that nothing passes through the three way valve into the drip tray until I relieve the pressure by removing the portafilter, regardless of whether the machine is on or off. Then I can see water coming out the bottom of the three way valve. That seems odd to me. Why would it be stuck until the pressure is released?

Jed (original poster)

#5: Post by Jed (original poster) »

Thinking this through further: the spring is sticking. Releasing water through the group is pulling the spring back open, then a little water can pass through the valve.

Solution: new nucleus or three way valve.

JRising
Team HB

#6: Post by JRising »

A new nucleus might solve it, or just lower your brew pressure. The only thing trying to return the nucleus to normal position with the drain open is that tiny spring, if the pressure in the brew-head is at or above the valve's rating, pressure will be holding the valve against the drain port. I see it in the Lucifer valves with the huge drain ports while back-flushing.

Jed (original poster)

#7: Post by Jed (original poster) »

A new three way valve took care of the issue and now the machine is working great.

Many thanks for the help!

Now comparing this machine to my semi-auto Pasquini I can say there are really only two things to like about the Bezzera:

1) It is significantly quieter. I'm not sure why, but the Pasquini is just way noisier, even though I've tried to make it quieter by replacing the pump standoffs and wrapping things in ceramic blankets. I suspect it is the metal case. I truly dislike the Bezzera case because it is a giant pain to take on and off.

2) The auto feature does make things a little simpler to stream milk when pulling a shot.

But that's it. Working on the Bezzera was way more of a pain than the Pasquini. Let's hope the controller unit lasts for many more years (knocking on wood as I type).

Thanks again for the spot on suggestions on the ribbon cable and flow valve.