Hi Robert. The yellow Sprague cap on the underside of the chassis with three wires contains two 10 mfd capacitors, each with a red wire on the positive end and a shared black common or ground. it’s not a 20 mfd cap. It seems that someone put that in to replace both original caps but it looks to me like there are two problems with that. 1) 10 mfd is not an adequate replacement for the 16 mfd. 2) they didn’t remove the original 16 mfd cap. Where the wire from the Sprague connects to the bottom of the original 16 mfd it’s simply making a connection with all the wires that should be part of that circuit. From the 16 mfd one wire should lead to your rectifier tube 6X5G and the other wire should lead to the speaker field coil.
I hope that’s helpful.