[Ron Ramirez]

The first Philco home radio to use an electrolytic was model 21 from early 1931. It used one very large Mershon, which was either 14, 16, or 18 uF, depending on who you believe. Even the (scant) Philco documentation available disagrees on the actual value of that Mershon. It was used as the input filter; the other filter capacitors were paper and enclosed in a large rectangular metal can mounted under the chassis.

Models 70 and 90, which came out months later, used two 6 uF electrolytics, either Mershon (copper) or Sprague (nickle plated).