SB2209 PT1000 5-20K Temp. difference and MAX31865 related components

Hi,

I have quite the temperature difference when running a pt1000 on the sb2209. For example, on idle it measures 14°C but it is actually 10°C, similary when the hotend is heated to 210°C, the actual temperature value is around 190°C. A difference of 1-2° would be acceptable but 5 or even 20?

Currently the pt1000 is connected to TH0 with the switch S2 pushed to the ntc side, and the klipper config I'm using is like this:
```
pullup_resistor: 2200.0
sensor_type: PT1000
sensor_pin: EBB:gpio26
```

First I thought it is the pt1000, that is defect, ordered a different one, same issue. Then, maybe it needs the amplifier, before I order the components, I tested the pt1000 on the octopus pro, since it already has the MAX318665 chip, there the same pt1000 reads the correct temperature values, well only the idle/ambient temperature, since the cable is no longer long enough to reach to the hotend.

Also I have a question related to the components, I could source all but the inductor L1 and S1. In the schematics it says 120R, but I can't figure out what value it should have, I think it is the blind resistance, but then i'm still missing the frequency, like it is for L9 to L12. S1 is not a big deal, since I could simply bridge it with a wire.

Start by reviewing the SB2209 schematic around TH0, S2, L1, and S1, then compare the reported configuration with the Octopus Pro and MAX31865 setup. Reproduce or analyze the PT1000 temperature discrepancy and determine the correct component specifications; done means the cause and sourcing details are documented or the issue is otherwise resolved.

Written by the indexing model from the issue text.