If anyone else worries about how hot R&S runs their unobtainium ADCs, here's how to run the fans a little faster and thereby obtain 10°C cooler running temperatures. If common knowledge is to be trusted, this should ~double the lifetime.
1. File > Maintenance > Service, enter "16052008f" into the Password field, and press the enter key. If successful, the text should disappear from the "Password" box.
2. File > Service 2 > Frontend Temps. Tick "GetHwTemperatures." Write down "FAN1 adjust" and "FAN2 adjust" (91 and 89 on mine). You can observe the thermal regulation by waiting for an ADC to wander above 100°C, watch "FAN1 adjust" briefly increase, followed by the ADC wandering back below 100°C.
3. Edit C:\ProgramData\Rohde-Schwarz\RTO\EEPROM\Frontend\Config.ini, changing ADCTEMP_OFFSET_CH* from -41 to -31.
4. File > Maintenance > Frontend. This is where shit gets real and I must pause for a moment to remind you that I am describing a procedure that worked on *my* scope, not selling you a free insurance policy for modifying *your* scope. Once you decide to accept the risk, press "Flash frontend EEPROM" and "OK." A dialog should pop up "Flashing device in progress, please wait. Do not turn off the device!" In about 5 seconds, the dialog should disappear and you should see "Flashing successfully finished." in the upper right corner.
5. File > Exit
6. Wait for a few seconds and restart RTx.exe. If you did not wait long enough, it will launch/exit, and you should wait a bit longer before trying again.
7. Once the scope app has started, the new settings should be active.
Verification 1: in a quiet room, you should be able to hear difference in fan speed.
Verification 2: File > Maintenance > Frontend > (scroll to bottom) > ADC temp offset should be the new value -31 instead of the old value -41.
Verification 3: File > Maintenance > Service > Password: 16052008f, (press enter, text disappears), File > Service 2 > Frontend Temps, (tick GetHwTemperatures), FAN1 adjust should now be consistently higher than the value you wrote down in step 2. On my RTO, under the ambient temperatures of my bench, the steady state FAN1 adjust increases from ~91 to ~115 after applying this change.
General background information: the EEPROM gets read from the frontend and written to C:\ProgramData\Rohde-Schwarz\RTO\EEPROM\Frontend every time RTX.exe starts. When you modify a ini or dat file in that folder and choose "Flash frontend EEPROM," the files in C:\ProgramData\Rohde-Schwarz\RTO\EEPROM\Frontend get written to EEPROM. Same goes for the mainboard etc.
Happy hacking!