I cleaned up the board some more though I could have used better chemicals to clean it with. So, I'm suspecting it's the PSU at this point. But I got interesting results.

Squealing is still there but softer in volume. But that depends on how much RAM I put into the LC. And which type I put in (8 chip SIMMs vs. 2 chip SIMMs - both 1MB SIMMs).

With no RAM, the Squealing eventually goes away.

With 8 chip SIMMs, the squealing is there but low in volume.

With 2 chip SIMMs, the squealing is louder.

I need to take apart my IIci (Don't want too!) to test the 4MB SIMMs in the LC and see what is the state of the squealing.