[morzh]

Connected the loop antenna, works very well. There is hum. Only noticeable when there is no station, and does not depend on volume. Was more pronounced when plugged through the isolation xfmr. Tried to rotate the plug, no effect. I decided to live with it.

If someone has a Hippo and is/was dealing with this problem, please let me know. It is not significant enough problem that I want to devote lots of time troubleshooting.

I polished it a bit, cleaned the chassis, washed the knobs with toothbrush and dish soap. One happened to be cracked inside, not visible and holds well, but was enough for the leaf spring to fall out, good thing I noticed.

Here it is assembled.