Better than my English and I’m English
Too complicated means that it has been over engineered. A power supply which is reliable and effective doesn’t need that many parts
Mastech power supplies have a couple of failure conditions. They are mostly reliable until they are not. What happens is the relay that switches the transformer taps dies after a bit and then the supply has to sink a lot more power through it than if the relay was working. This causes the pass transistors to blow up and go C-E short dumping the entire voltage on the pre regulated stage of the supply into your circuit. This happens a lot. I have fixed perhaps four units that have done that.
Why HP supplies? The design originated in the 1960s and been incrementally improved since then. That’s 50+ years of fixes in there
. E3630 because it is three power supplies in the same box so you can see what they did to handle different voltage scenarios.