[Ron Ramirez]

What is the part number of the power transformer in your 51 chassis?

It does look like the cable carrying power to the SW converter chassis, coming out of the 51 chassis, was added at a later time. I don't think Philco would have used a rubber grommet - I think they would have used a fiber grommet, like the one which the AC cord goes through.

Oh, and Ben, the differences between a 70 and 470, and a 90 and 490:

Both upper chassis use larger power transformers which are capable of supplying the extra current for the B+ and filaments in the SW converter chassis. In other words, you can't just stick a 90 chassis in that cabinet, add the cable, and be done. You will need a power transformer which can handle the extra load of the 90 chassis plus the SW converter chassis. A power transformer from a Philco 112, for instance.

The same goes for the 70 chassis. It would require a power transformer from a single 47 model 90 to handle the extra load.

And the same would go for the 51, if it were original - it would need a larger transformer capable of handling the extra load.