Rigol DS1052E repair question

[Vytautas]

Hello,
could anybody help me with repairing my DS1052E scope? Some time ago, it started going crazy. At first it started showing signs of working normally in long memory mode only. In normal mode, the waveform was not possible to contract in the horizontal scale, as it would freeze when trying to see more of the waveform on the screen, and had to be expanded to start sampling again. Then, after a few minutes of work, when it warms up, it goes crazy (shows whatever) or freezes totally. I tried to blow cold air on the FPGA and when it cools down, it would start working again. I tried resoldering the FPGA a few times, the problems did not go away. Now, I ordered and soldered a new FPGA, but the problems are not gone, even though I monitored the process very carefully (preheated the board, used leaded balls, and a careful temperature control, it never exceeded 220 Celsius, and the FPGA nicely sat in place). Is the FPGA still the culprit, or should I look somewhere else? Got tired already with this stubborn thing. Could anybody help me, please? Going to sleep today, its late, and I am frustrated.

[lowimpedance]

 As it appears thermal I assume you have checked the fan is running at the correct speed? etc. And (not being familiar with the main PCB) is there any local voltage regulators etc  that are playing up due to dodgy bypass caps !.

 I also have a faint recolection that some reversed enginneered schematics are some where on the forum too, might be useful.

see here:
https://www.eevblog.com/forum/blog/rigol-ds1052e-nasty-surprise!/msg56070/#msg56070

[Vytautas]

Hello again.
Thanks for reply. I tried to check some things.
First, I checked the voltage supply for the EL1881 video sync separator (marked 102). According to the reverse engineered schematics supplied online, this supply should be +5V. It reads 3.3V there though.
Another thing. When soldering the Altera FPGA, the "DEE" component, marked "1" was moved out of place by accident. I soldered it back the way shown in the picture, which I downloaded from a teardown. But now I noticed that the "DEE" marked "2" is upside down in my scope compared to this image! How could this be, if I had never touched it and the scope was bought new?! And what is the DEE? Could not google it out.
Thank you.

[PA0PBZ]

As far as I can see 102 is a resistor array , not the EL1881, so what the voltage at the pin should be remains uncertain.
The parts marked DEE are also resistor arrays, probably 4 resistors across, so the orientation makes no difference.