The solid-state rectifier in the reissue bassman... like the urethane finishes and 3-bolt necks of 70s Fenders... is the easiest thing to identify about those amps that's different from original.
And perhaps because it's such an obvious difference, it usually gets most of the blame.
But you know what? In my opinion the solid-state rectifier was one of the more minor issues with that first bassman RI.
Right off the bat, the 12AX7 input stage (rather than 12AY7, as on an original 5F6-A) was a deal-breaker. Wrong gain structure for that amp, wrong sound from the front end. A 12AY7 is a very different tube from a 12AX7, even though one will "work" in the other's spot, to some degree. Yes, the AX7 offers roughly twice the voltage gain, but it also has a somewhat different transfer characteristic and audibly different character. Big miss. No new production 12AY7s when it was introduced, so they had to do something, but... it just didn't work.
Then, of course, while the Eminence speakers were actually decent for their time period and price point... they were no P10Q, that's for sure. So that was another BIG one, along with the overall quality of available parts.
But another HUGE one was the cabinet construction. Original narrow-panel tweed Fender cabinets were PART of the instrument. Not just "a box to hold the speakers." 1990s Fender missed it, big time. They apparently saw the cabinet as a good place to cut corners, perhaps wrongly assuming it wouldn't impact the sound much.
They were wrong.
A narrow-panel tweed cabinet is solid finger-jointed yellow pine with a plywood baffle. The baffle is skinnier ply than it rightly SHOULD be-- 3/8" on the bassman (1/4" on the Princeton and Champ!), and is hung by four screws-- two on the top of the cabinet, and two on the bottom.
As a result of the ply being SO skinny, and being TOTALLY free on the sides... it vibrates WITH the speakers almost like the top of a giant plywood double-bass, or enormous guitarron or something. The baffle itself is almost like a fifth "speaker" in a way. This motion, in addition to producing sound all its own, also influences the sound of the speakers that are mounted to it.
The rest of the cab, being solid pine, is also pretty damn resonant. You can crank one of those bassmans (bassmen?) up and almost bounce it off a chair, it shakes so much. This is part of the amp's characteristic sound.
The reissue had a thick MDF cabinet and thick baffle made of who-knows-what. It exhibited none of those behaviors.
Yeah, and I guess it had a solid-state rectifier, too. I mean, not that the 5AR4 "sags" that much anyway. It's not exactly a 5Y3. The 5AR4 was a damn stout rectifier, top state-of-the-art until tubes themselves fell by the wayside. It was chosen precisely to AVOID sag, and I never personally felt an original Bassman "sag" too much (sure as hell not with a guitar through it, anyway).
But the input stage and the cab were deal-breakers for that amp being anything like an original.