Zenith 146HP movement servicing

I found a local watchmaker who has worked in Omega center before and he just finished servicing my 1969 Speedmaster. This is good news for me because in Estonia there are no other watchmakers who want to work on old chronographs.
Anyway, I asked him if he would replace the mainspring on my LeGant Zenith AH2711.
He asked me if there are any service technical info about this movement.
I have searched everywhere and couldn't find any.
Does anyone have info?

For example like these for Omega cal 861: http://www.chronomaddox.com/omega/manuals/service/861/1600w/

I can’t remember which exact site but I think I saw the movements listed on a parts supplier website like Ofrei.

I also asked from Zenith, but they won't share this information 😀

You have to ask/search for the right thing 😉
The Zenith 146HP is an Martel 14```:
https://www.watchuseek.com/threads/...rtel-watch-co-and-zenith-chronographs.660565/

It started as Martel 749 than it was Universal 285 and then Zenith 146.

Thank you!

Maybe this helps:
https://www.cousinsuk.com/PDF/categories/1647_Universal Chronograph 281, 285, 289.pdf
https://www.cousinsuk.com/PDF/categories/1646_Universal Chronograph.pdf