I was lucky that I caught the leaking NiCd battery in my 7A42 back in 2016, when
it was still in the early stages. Surprisingly, the only damage was to the nearby
jumper plugs, many of which had seized and became encrusted with blue crystalline
deposits. This damage was not immediately obvious -- one had to examine contacts
inside the black plastic plug housing.
Amphenol still makes identical jumper plugs today (Mini-Jump p/n 65474).
I should note that I had decided _not_ to replace the battery, as any new NiCd
battery will just cause more of the same damage if allowed to run empty.
(And, depending on the quality of the replacement battery, possibly much
sooner than the original part made by Saft.) This is not suitable for a unit that
only sees occasional use, and where the hope is to preserve it for many years
into the future.
If the battery is not replaced, then it is important to move the BE (Battery
Enable) jumper to the open position, to stop the plug-in from attempting to
initialize the front panel settings from invalid memory contents. With the BE
jumper in the closed position, and no battery, the plug-in can occasionally
lock-up during power-up.