V+ and V- from 24v dc

[loop123]

The  data sheet says an absolute maximum of ±18V, so it should be fine.
https://www.ti.com/lit/ds/symlink/iso122.pdf

But remember a pcb contains all other components. Usually what components can't survive past 18V (+, -)?  Transistor? diodes? capacitors? resistors? ordinary ic? etc?

[Zero999]

The  data sheet says an absolute maximum of ±18V, so it should be fine.
https://www.ti.com/lit/ds/symlink/iso122.pdf

But remember a pcb contains all other components. Usually what components can't survive past 18V (+, -)?  Transistor? diodes? capacitors? resistors? ordinary ic? etc?

It's impossible to answer that question without reverse engineering it to some degree.

There are parts on the board which might be damaged by 18V, but it depends on how they're connected. For example there are parts which are only rated to 5V, but there appears to be a voltage regulator: VRx, the TO-92 part, on the left hand side of the board, near the red, yellow and brown wires cabled tied together.

[brucehoult]

It's a type of package. Many different parts come in this package style.

https://en.wikipedia.org/wiki/TO-92

Looks like LM336, a 2.5V "reference diode".

[loop123]

Guys. While you still remember a bit the circuit and before you forget them. I want to know if any noises can couple to the main unit and is it better to have a separate power supply for an isolation head that connects beween main units and electrodes? I'm fixing the connectors of the isolation head and need to decide whether to create separate dc pack for this instead of getting it from the main circuit shown earlier. Thank you.