A tiny update...
The 2236 is successfully apart. I did find the CH1 probe sense problem, apparently TEK forgot to solder the W9100 connection on the A3 board, the wire was in the PC board hole, just unsoldered. Still investigating for other connection problems that might be the cause of the "Control Button Error" message.
As long as I am inside, I am going to replace the "Riga" filter caps, too.
