---- Micro-controller kaputt -----

[haguedick]

Hallo,

During march 2009, I got a Saeco Vienna which was faulty.
With your help, i have repared it, the micro-controller was kaputt, it has been removed and an other one has been placed on a support.
All was ok during 6 months until last week it became faulty.
I found the Bruhgruppe in high position, cafe was done but i can't say if cafe was finished.
My investigations shows that micro-controller is kaputt (200mA!/5V on external power supply pin 14 and 28).

I have checked printed circuit board, all seems ok.

Before placing an other controller I 'd like to know if you have some ideas on what happened and what could be faulty.
No triac seems to be in short circuit.
I wonder if overvoltage could cause same damage, in this case 5.6V zener could be faulty: lot of questions!

If i have to place a micro controller every 6 months the cafe could become bitter!

Danke
Dom

 

[ksb]

Hi dom,

did you replace the zener-diode too ?

regards KSB

 

[haguedick]

Hello KSB

Yes, I think because in march due to a fault when mesuring voltage with oscilloscope zener became
in short circuit. I have replaced 5V regulator, zener-diode and 470uF capacitor.
I don't remember if the zener was...new, i hope!

Regards
Dom

 

[ksb]

before replacing the controller make sure that there is no higher voltage than 5V at all pins of the empty ic-socket (with all plugs connected). Take care that even the mains-synchronization (R10, R9, D13, C2) is in good condition.

 

[haguedick]

OK i will check the is no higher voltage than 5V and control mains-synchronization.
I think i will replace zener 4.7V and 5.6V, i will have no doubt with them in the futur.
Now, i have to buy a new micro-controller.
I will give news in few weeks

Thanks a lot
Dom

 

[haguedick]

Hallo,

Some news about Vienna.
I have replaced controller, 5.6V and 4.7V zener diode.
After removing zeners i have checked them: they were in good working condition.
Since 2 weeks ago Vienna is making good coffe.
It works but i'm not very satisfed, i think there is a component which sometimes become faulty.

Have a good week-end
Bye