Canon A-1, exposure memory and exposure preview switches

[Nikos72]

It seems that after years of not using it I have either forgotten using my A-1 properly, or there is something going wrong with it.
I have an FD 50mm 1.8 S.C. (breech lock) mounted on it and when in Av, or Tv mode it seems that the exposure memory switch does not lock the exposure. I press it, and while recomposing the frame the exposure changes while I still hold it pressed.
Also, when trying to preview he DOF, I shift the aperture from A, to say f/16, press the exposure preview switch, but the lens does not stop down.
Am I doing things wrong? Is my A-1 and/or the lens damaged?

[icebear]

Use a fresh battery and consult the manual.

[Nikos72]

I did so, but either I don't understand what the manual says, or I am doing it the wrong way.
Is the exposure memory actually the exposure lock on the A-1? Or is it just to hold and alter the shutter/aperture from the dial? Does anyone know how it is being used?
Also, for the other switch, the exposure preview one, there are not many words other in the map of the camera in the user's manual.

--- Edit ---
Upon more carefully reading the manual I have discovered that:
1. The exposure memory locks the EV of the exposure and not just the shutter/aperture pair.
2. The exposure preview switch just makes a reading of the exposure in the viewfinder.

Read the damn manual. The million dollar advice that me not follows every single time!