[adamrobertg]

I recently acquired a Philco 90 locally.  This is the "mid" model with one 47.  The cabinet is actually very nice and has a good original finish.

When I pulled the chassis out, I noticed that at some point in the past it had a catastrophic power transformer failure.  Tar everywhere, and tar residue all over many components.  Sometime possibly in the late 90's, a replacement Stancor transformer was installed along with a filament transformer for the output tube, the electrolytics were replaced, the 3.5k section of the bias resistor was bridged, and one capacitor and resistor was replaced.  This is in addition to a number of bakelite blocks bypassed with paper caps many years ago.  This was clearly a well-loved radio.  I should be able to clean up most of the tar with a heat gun and lots of paper towels, and the new transformer plus filament transformer seem correct, at least.

I may be wrong, but I suspect this was the work of a local shop that opened in the 1940's and closed in the early 2000's.  They specialized in tube electronics, but had a repair-only mentality.

Unfortunately I'm not sure I understand what they were doing with the electrolytics.  The first filter is two 22uf 450v caps in series, negative to center tap, with a smaller modern 250v electrolytic cap connected from center tap to ground (positive to ground).

The second filter cap still has an ancient cap from the 50's connected, though it's taped together and the repairman may have not noticed it.  An additional modern cap has been installed from the far side of the 3.5k section of the bias resistor (other side of the field coil), with the negative to ground. 

Normally if I get a set that's been worked on in the recent past I'd power it up slowly to see where it's at.  Since this seems so... wrong... I don't think I want to do that.  Should I be putting this back to the schematic?  Or did the last person know something I don't?