In the 128/512/Classic/Classic II, yes. PSU and CRT circuitry are all intertwined, and separating them completely is very difficult I would think.
The SE and SE/30 have separate PSUs, however, so it would be trivial to isolate whatever wires serve the LB and cut off/reroute the rest.
How do you plan to get video out? A PDS video card?
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