H
henjo
Teetrinker
- Dabei seit
- 07.08.2011
- Beiträge
- 2
Hi,
I have a Saeco Vienna which unfortunately is broken after the the microcontroller was fried during at the end of the grinding phase with the electromagnet that releases the grounds into the brewing group.
I ordered 2 new microcontroller replacementboards. Since I couldn't see any damages or burnt components I tried one of the controllers.
But unfortunately whatever killed the old microcontroller killed the new
one. It was good I ordered two of them, but before trying the next one
I want to be sure what is killing it.
What happened was that it started all fine and made the cleaning cycle
of the brewing group and I tried the water purge program by pressing
and holding the steam button and it worked fine. But when I started a
normal brewing the grinder started and ground for some time and then
it stopped. The electromagnet that controls the release of the
coffeegrounds into the brewing group was never activated.
And when I measured on the broken controller I got a new 1ohm short
between pin 28 and 14. But the protection diodes on the other inputs
of the circuit seemed to be ok. So I suspect that it was a surge on
the supply that killed it.
The problem is that all triacs and everything else seem to work. I
took the advice in the instruction to replace the electrolytic caps at
the input of the voltage regulator. I even measured the ripple at the
input of the 7805 before and after the new cap but it was the same,
about 1.7V p-p so I doubt this will help.
I have also tried to activate the grinder and the electromagnet
manually without microcontroller and measured on all 28 pins of the microcontroller with an
oscilloscope and it was a high frequency disturbance about 0.5V
peak on some of the pins and especially the 5V when running both the electromagnet and grinder.
I have discussed the topic with dicofema and they forwarded the questions to hmilbradt.
And he was kind to answer and suggested this:
> "The CPU was lynched after a short time during milling. My guess is a
> rollover on the JP14-signal lines under the 4Ohm7 resistance."
>
> Try to search for this Problem.
When I looked under the 4.7ohm resistor it looked like burnt varnish under the inductor and I had some resistance between the inductor and JP14 but it was about 5Mohm which shouldn't be that dangerous. But after removing the burnt varnish I didn't have that megaohm contact anymore at least.
I cannot think of anything more I can try to be sure my last microcontroller will share the same fate as the rest.
Best regards,
Henrik
I have a Saeco Vienna which unfortunately is broken after the the microcontroller was fried during at the end of the grinding phase with the electromagnet that releases the grounds into the brewing group.
I ordered 2 new microcontroller replacementboards. Since I couldn't see any damages or burnt components I tried one of the controllers.
But unfortunately whatever killed the old microcontroller killed the new
one. It was good I ordered two of them, but before trying the next one
I want to be sure what is killing it.
What happened was that it started all fine and made the cleaning cycle
of the brewing group and I tried the water purge program by pressing
and holding the steam button and it worked fine. But when I started a
normal brewing the grinder started and ground for some time and then
it stopped. The electromagnet that controls the release of the
coffeegrounds into the brewing group was never activated.
And when I measured on the broken controller I got a new 1ohm short
between pin 28 and 14. But the protection diodes on the other inputs
of the circuit seemed to be ok. So I suspect that it was a surge on
the supply that killed it.
The problem is that all triacs and everything else seem to work. I
took the advice in the instruction to replace the electrolytic caps at
the input of the voltage regulator. I even measured the ripple at the
input of the 7805 before and after the new cap but it was the same,
about 1.7V p-p so I doubt this will help.
I have also tried to activate the grinder and the electromagnet
manually without microcontroller and measured on all 28 pins of the microcontroller with an
oscilloscope and it was a high frequency disturbance about 0.5V
peak on some of the pins and especially the 5V when running both the electromagnet and grinder.
I have discussed the topic with dicofema and they forwarded the questions to hmilbradt.
And he was kind to answer and suggested this:
> "The CPU was lynched after a short time during milling. My guess is a
> rollover on the JP14-signal lines under the 4Ohm7 resistance."
>
> Try to search for this Problem.
When I looked under the 4.7ohm resistor it looked like burnt varnish under the inductor and I had some resistance between the inductor and JP14 but it was about 5Mohm which shouldn't be that dangerous. But after removing the burnt varnish I didn't have that megaohm contact anymore at least.
I cannot think of anything more I can try to be sure my last microcontroller will share the same fate as the rest.
Best regards,
Henrik
. 
