93 740i - Instrument cluster voltage varies

On my E32 '93 740i the instrument cluster voltage seems to fluctuate. The gas gauge has worked very
rarely for months. The message display got very bright then went dead. Then the speedo and tach started making wild swings. And the temp gauge went dead. Seems like a voltage regulation problem. Is there a separate voltage regulator for the instrument cluster, or cluster and some other stuff, if so, where might it be located and is it likely causing this problem? Or is there just the main voltage regulator on/by the generator and that should be replaced. Thanks, Ron

Update on voltage variations in E32 instrument cluster:
Bought the E32 manual by Bentley, it was great.
Didn't show any external voltage regulation, just main regulator on/by alternator.
Would have bought the Bentley book years ago if I knew it existed.

Swapped in a replacement cluster from a 1994 E32 and it worked fine.
Also tried a cluster from a 1988 E32 ( 735i ) which was not supposed to be compatible.
The 1988 cluster worked just fine, except the odometer and trip odometer did not.
They are wired differently up to 1991, again, all seemed to work, except OD and trip OD.

The replacement cluster has worked fine for 2 days and 10 miles.
So likely the voltage regulation is done on the circuit board inside the instrument cluster.
Problem likely solved. The circuit board went bad and likely too-high voltage fried the gauges
and the display one after the other. Cheers, Ron