can a techmarine use terminator armour ? (assuming he has the renown and requsition) or is there something about techies which means they cant (get fitting a servo arm or harness) I dont think there are any examples of a techmarine using terminator armour in the TT fluff but could be wrong

So far as I know there is no rule against it. it is easier for them to get artificier armour, which might dissuade them from it. The servo arm is unlike other cybernetics in that it is attached to the armour, and is fairly detachable compared to other cybernetics. personally I would rule that it could be attached to terminator armour instead by expert tech priests before the mission, however I could see why other GM's might rule that if a techy wants termy armour he has to leave his servo arm behind.

So to sum up, it is definitely possible imho, but it might require the techmarine to give up his servo arm in exchange

Personal opinion is no a techy shouldnt be able to use termy armour. The servo arm and harness functions through a special back pack attached to the techys coil and armour. There is no room on termy armour for this. besides the flesh is weak talent should more than make up for the armour points. Give em artificer armour instead!

The Emperor protects

I see no reason why a techmarine couldn't wear terminator armor. Of course a techmarine in terminator armor will not have his servo arm. The rules for terminator armor limit what equipment may be loaded on them. A servo-arm is not in that list. And honestly, what self respecting space marine would disrespect such an ancient and revered relic like a suit of terminator armor by cutting it all apart just to add a servo-arm for a single mission or two?

Victris said:

Well, I think he is able to use it. A MOTF can remove his servo-harness and mount a Conversion Beamer according to the codex, so temporary removal is possible. It's just more frequent that a Techmarine wears Artificer armour (again going by 5E Codex). I can see why: you get very good protection and can use your servo-arm (or even better servo-harness).

Alex

maybe make a relic that he can take to combine a special suit of terminator armor with a servo-arm/ harness. This would make him work harder for it and would be more of a reward. Just my opinion on the matter

Shouldn't Techmarines be especially eager to hop into a suit of Terminator armor due to their appreciation for the technological marvel it is?

I know in the tabletop you could field Terminator Techmarines in a Terminator command squad. Any given chapter probably has at least one Techmarine attached to the 1st company who is so equipped.