Elektronik Incanto Deluxe (SUP021YDR) cannot start

[negrusti]

Need help, Incanto Deluxe (SUP021YDR) cannot start after I changed the settings for the off/on timer (but that might be a coincidence).
Now it only shows a single row of black rectangles on the LCD screen, no mechanical sounds.
mechanical and electronic knowledge available - yes
meter available - yes
Thanks
Gregory



Um dir schneller bei deinen Problem zu helfen, bitten wir dich folgende Angaben zu machen:
- Mechanik- und Elektronikkenntnisse vorhanden ?
- Messgerät vorhanden ?
- Genaue Bezeichnung der Maschine

 

[negrusti]

Output from LM2940CT is 4.95V, normal I guess?

 

[hmilbradt]

Hi,

The voltage is in the proper range. But the rectangles in the display tell you .... the microprocessor does not boot.
Check the temperature sensor und its associated signal circuit. A fault in this area prevents the CPU from booting.

regards
Harry

 

[negrusti]

The sensor resistance is ~2000 Ohm, in line what the service manual says it should be for my room temperature. I already replaced the voltage regulator and both electrolytic capacitors next to it. In fact machine started one more time, after many hours of being turned off, but then I switched it off and on, and machine does not boot again. How can I check the sensor signalling circuit?

 

[hmilbradt]

In fact machine started one more time, after many hours of being turned off, but then I switched it off and on, and machine does not boot again.

Hi,

Does the 5 VDC power supply contain a temperature sensitive part ? Is the creation of a stable 5 VDC voltage and the CPU reset pulse too slow ? Check the power supply using a suitable cooling spray.
I also suggest to replace the electrolytic capacitors on the CPU-board using types with a higher 105°C temperature limit.

How can I check the sensor signalling circuit?

X_Temperatur_P120CPUV03-Markup.jpg ...... the capacitor C14 is the weakest part.

regards
Harry

 

[negrusti]

Thank you, I will replace the electrolytes on the CPU board first and will post the results.

 

[negrusti]

Did not replace the electrolytes on the CPU board yet, but I kept the CPU board in a freezer for an hour and it starts OK after that.

 

[Grisu]

if changing capacitors doesn't help maybe the transformator is going to die, there are cheap replacements (e.g. Conrad).
Or remove 7805 and try with stabilized 5V power-suppy to see if the fault is belonging tu the supply.

Regards Grisu

 

[negrusti]

Wait a second... Now, when the whole machine has been off for many hours, if I just connect the CPU board to the power supply board with the ribbon cable, and nothing else is connected to the CPU board, it boots fine (showing "DREGDRAWER MISSING" as no sensors are connected).
If I try to power on the CPU board separately by supplying +5V from a lab power supply to the pins 1 and 2 of the ribbon cable (not using the internal power board), then it is not booting (showing the same "squares bar").
These are the repeatable results. That means that I am not supplying some signal / voltage over the ribbon cable. Does anyone have the functional pinout for the ribbon cable?

 

[negrusti]

Is the reset pulse generated on the CPU board or on the power board?

 

[hmilbradt]

Hi,

The reset pulse is generated by IC4 = TL7705A on the CPU board ...... http://www.ti.com/lit/ds/symlink/tl7705a.pdf

Does anyone have the functional pinout for the ribbon cable?

There is no official pinout listing of the ribbon cable. Usually the infos between power board and CPU board may be divided into three catagogies ..... 1. CPU 5 VDC power .... 2. triac gate signals CPU board to power board ..... 3. the CPU needs infos from the power board a.) about the power drawn from mains by the grinder (via ISO 10) and b.) infos about the actual state of mains versus time (via ISO 11) in oder to switch the triacs at zero voltage crossing of mains.
The power board creates the infos needed according 3.) with the parts shown in the attachments ......

regards
Harry

 

[negrusti]

The reset pulse is generated by IC4 = TL7705A on the CPU board

Aha!
And if I am guessing right, the capacitor C3 then controls the duration of the reset pulse, 4.7 uF should give ~ 120 milliseconds. And on my board this is a capacitor by CapXon, which is known to make bad capacitors...
Waiting for the electronics shops to re-open after NY...

 

[Grisu]

sorry, my fault, cant work with lab-power, as the CPU needs the sinus-waves from the 230V power-supply.

I think your machine has partly similar circuits than the standard incanto, maybe its a help to you (last page V10): Schaltungsunterlagen Incanto SUP 021Y

Regards Grisu

 

[negrusti]

Replacing electrolytic capacitors resolved the issue! I am tempted to believe that it was the faulty C3. Thank you very much hmilbradt!

 

[hmilbradt]

Hi,

Congratulation and thank you for the feedback.

regards
Harry