Basetech BT-305 missing resistor

I just modded my Basetech BT-305 laboratory power supply to become an IoT device.

Everything works as planned, except the volt display in the multimeter-part of the supply, which is directly shown below. I disassembled the display part and saw a missing resistor, but am unable to find out how many ohms it had, as I am not an electrical engineer, so I hoped you guys could help me.

This is the problematic part:

I also found the circuit diagram PDF on the page I bought this device

I bought the above from Basetech BT-305 Labornetzgerät, einstellbar 0 – 30 V/DC 0 – 5 A 150 W Anzahl Ausgänge 1 x

In case anyone has the same device and has a picture of this part, that would solve the problem of searching for the right resistor immediately.

EDIT:

A high-enough resistor that would fit in there is 0.5 kilo Ohms. This was measured by using a very high potentiometer and slowly decreasing the resistance until it worked as it should. Thanks to William for the idea in the comments below.

EDIT 2:

As there seems to be interest in how i modded this device for iot in the comments.

the goal is to switch the output on/off over the internet (app/http requests)

In short: disassembled the device, added a second AC power plug (female) into the bt-305, so that a 5v wallcharger could be powered in the case. The 5v charger is used to power a “Sonoff SV” which is an esp-based smart switch from itead. The sonoff sv supports a so called “isolated mode”, which means it input is 5v, and the 2 output pins just short each other when getting the command to switch, acting like a normal switch on 2 cables. Those output pins are soldered to the pins of the “output” button of bt-305, so sonoff is just simulating a button press. Sonoff has an app to communicate with the switch, or you can connect it to IFTTT and send http requests to a rest-url via web-hooks to set the state of the switch. I generally use the app, as it supports “inching mode” which means the switch-output gets shorted for just 0.5 seconds, which is necessary to simulate a button press.