Saeco Stratos problem

[alexallex]

Hi,

I have a little problem that I'm dealing with. I have a bricked Saeco Stratos, similar problem like here : stratos problem . It is unclear for me if that person succeeded to fix his coffee machine (via Google translate). I do not speak or understand German so I cannot search the forum for more information about this problem I have. Is it possible to fix this issue without changing the circuit board?

Thank you!
Alex V.

 

[Grisu]

He changed the electronic board as his was dark and no function.
Then display got lighted but not visible, so he had to change display too.
At the end it was working, only he asked one more question about resetting, but he shouldn't do so.

 

[alexallex]

I found this solution but I cant understand the google translation. -> Elektronik - Siemens TC55, Display-Beleuchtung geht, sonst nichts

Can you help me please?

 

[Gastroharry]

Dein Problem gehört ins Stratosforum!
Und dort solltest Du die Eingangsfragen beantworten.
Wenn nichts mehr leuchtet kann der Trafo defekt sein.
Auf der Lötseite kann man messen.
Primärwicklung ca. 2,1 kOhm ---- Sekundärwicklung ca. 15 Ohm.

 

[ksb]

Hello AlexAllex,

in the the first link stratos problem the problem was a dark display - the issue could be solved by buying a new electronic and display board. Later he tried to repair his old defective board - here we don't know what happened.

In the second link Elektronik - Siemens TC55, Display-Beleuchtung geht, sonst nichts the display was lit but the electronic supply voltage was too low (4.6 instead of 5.0V). After replacing the electrolytic capacitor (470µF / 35V / 105°C) the problem was solved at the end.

Please notice that at least the temperature sensor must be connected for testing - otherwise the display would show black squares only.

Best regards
KSB

 

[alexallex]

I have replaced all the capacitors. Still I have the same error. Could it be the converter?

 

[ksb]

What kind of error do you have exactly? Did you measure input- and output-voltage of the voltage regulator? What are your results?

 

[alexallex]

The display is lighted but that's all. No command works, no text appear. Sometimes when I power up the machine from the switch some blocks appear but disappear immediately. I don't know how to test the voltage regulator. I saw some videos on youtube but I'm still not sure. Do I have do dispatch it from the board?

 

[ksb]

You have to measure the DC input- and output-voltage of the voltage-regulater IC3 (LM2940) which is located near to the 470µF electrolytic capacitor. There is no need to unsolder the component for measurement.

The input is on the left side, GND is in the middle and the output is on the right side (if you look on the top of the component).

 

[Gastroharry]

Messe den Widerstand an Kabel Grün/Grün.
Thermosensor am Boiler.
Sollte ca. 1900 Ohm haben.

 

[ksb]

Additional hint from Gastroharry:

measure the resistance between both green wires of the temperature-sensor: target value 1900 Ohm @ 20°C (for this measurement do not power the machine)

 

[alexallex]

Voltage regulator: IN 14,00 - 14,22V alternating between this values; OUT: 4,97V constant;
Temperature sensor:1912 Ohm at ~22°C

 

[ksb]

This measurement result looks good. Now you have to measure the reset-pulse at pin 5 of the 7705 voltage supervisor near to the CPU. Target value: 5V stable

Best regards
KSB

 

[alexallex]

Need a little more help please. How to measure it, what do I connect?

 

[ksb]

Connect the black terminal of your meter (range for example 20VDC) to GND (for example the heatsink of the voltage regulator) and the red terminal to pin 5 of the voltage-supervisor. The target value is stable 5V.

 

[alexallex]

result: 4.97V

 

[ksb]

Do you own some more measurement equipment (isolating transformer, scope)?

 

[alexallex]

Unfortunately no. Only the multimeter. What do you suspect is the problem?

 

[ksb]

Hello Alexallex,
a) It would be helpful to know that the supply voltage and the reset-signal is really stable without any glitches and spikes.
b) Maybe there is an issue withe the temperature-measurement circuit which can only be detected with a scope.
c) Another problem could be the zero-crossing-signal.
Best regards
KSB

 

[alexallex]

Hi. I have remeasured TL7702
ref - 2.5v
resin- 4.97v constant
pin 5 every 1 second jumps between 2.5 and 4.9

From the datasheet of TMP87PM40AN on reset pin connected to pin 5 of TL7702 shoul be constant ~5v
After unsolder pin 5 of TL7702 from CB and connect directly pin reset of TMP87PM40AN to 5v, pump, boiler and coffee valve opens / run continuously , the display is not displaying anything just blocks at start.