Bob Engelhardt wrote:

Pete C. wrote:
Absolutely those are SCRs or Triacs, you can see the control terminal in
the first picture on the #8 device. ...

Actually, those are 4 terminal devices - there are 2 control lines
(black & white) for each. What does that make them? Bob

Nope, most likely three terminal. The two small wires are the control
terminal and the reference connection to the main lead. The reference
connection is at the device, so that it is not affected by the high
currents / voltage drop in the main lead. They are/were probably driven
by an opto isolator on the missing control board.