I have a HP E3615A. Bought it used, about $90, made 1997 and still going strong.
A good design, mainly through hole, no fan, low ripple. There are many connections at the back that can be used for many things like, using sense wires, connect many PS in series or parallel, remote voltage adjustment, etc. Mains voltage setting can be changed inside by switches.
There is no output on/off switch but the output is well controlled when using the main power button. On my unit there is a small spike when turned on before the voltage start raising (if I remember correctly 9us, 3V, no change with load). If that's a problem, it's easy to suppress by connecting a big capacitor over the output, I have seen that on other Agilent supply, for instance on E3631A in a tear down here on the forum.
On the bad side; easy to accidently change the voltage setting when connecting wires, if tripping the over voltage protection you have to restart the supply (maybe good..).
The service manual including the schematics can be found on the Agilent site.
I have some pictures and measurements on it which I plan to post in a new tear down topic.