I had a TL Electro, totally mechanical with built in meter.
Being Brian says the Aperture has no electrical connection then its as I initially suspected, a mechanical issue where the aperture lever in the body or the shutter release linkage has come loose.
In post 3 you state the shutter works fine without a lens attached so when a lens is attached and set to minimum aperture the lever blocks the operation of other levers.
To fix this you will need to peel back the leatherette on both sides of the lens mount, remove the lens mount and possibly the mirror box itself, not an easy job.