DeLonghi ESAM5500 shows general error

Hi all
,have a problem with my ESAM550 Cappucino.
At some point came "General error" and the brewing unit stopped at the top.
Have the machine then brought to the repair. There, a defective thermoblock was diagnosed and also replaced.
But the error is still there. The dealer thinks that it would be due to the display board.
I can not understand.
Can someone help me?
The machine is an heirloom and I am very attached to it.

Thanks for your helpGregor

In test mode times test all functions. If he has enough parts and can test another display then it would be ok, but to start replacing on suspicion will be expensive.
Was only the heater renewed or the complete thermoblock including temperature sensor?

Have today checked the functions via the self-test.
With the "2-cup button" the brew group goes up. After that, it only hums. The brew group seems to be at the stop.
But does not go down anymore.
Everything Andre seems to work

It is best to open the machine. Unscrew the back, side parts and top.
For the upper part you must loosen the screw in the Verstellhgebel of the grinding degree.
Then see if the upper limit switch is actuated.

Was the drive down when you started the test mode? Or does it move to the home position when you unplug the machine and plug it back in?

The upper limit switch is not actuated. The TB is corroded and the housing around the piston no longer moves.
However, I was told that the TB was changed and the general error still comes.
I will order the TB again.
Is the limit switch on the TB the cut off for the brew group?
What should I replace first, the power board or the control board, or the reed contact board?

The switch on the thermoblock is the upper limit switch. When the is reached, the motor switches off.

The question is what the drive looks like. Whether it is defective and the brew group does not come up far enough.

The thermoblock you have to replace probably definitely. But why he does not go down in test mode should be explored first.

If you unplug it from the mains and plug it back in, does the drive run or run in the home position?

The TB I will have to order new in any case.
Have times in test mode checked the BG.
The limit switch works. In test mode, the brew group goes up, if I manually trigger the limit switch above, the BG also goes down again.
The display also shows both limit switches.

After a restart, the general error occurs again.

The BG definitely goes up, but there is no movement at the piston, so the limit switch is not activated.

What else can be tested, or what should I replace?

Replace thermoblock. After that let's see how the machine behaves.
Would perhaps still take the reed board. The cost is not much and is often broken. The measures the path of the drive and if the does not fit also comes a fault.