[quaddriver]

I hate to ressurect old threads, but almsot 5 years later I have found one of these radios, intact, complete, pretty and of course not working.

I have the Rider schematic for the 75P6 and like the OP noticed, it is very different, especially in the area of the power supply.

the OPs pics line up with what I see, there is a 2nd transformer between the filter cap and the output tube that is used as a resistor between the rectifier cap section A and B which then goes to the actual output transformer.

Also missing are the 470ohm resistors (many sets use a 1Kohm resistor to drop the voltage from the first cap section to the voltage used by the rest of the plates, I find a 390ohm 2 watter carbon comp in there. Plus a lot of other differences to darn near make the schematic unusable.

In the intervening 5 years does anyone have a line on the 75P6U model? Beitman does not, Im getting no hits for Sams and Rider just has the non-U version.

Also of curiosity is a 5mfd 50v wax cap with a + end marking where the + is on the B- and the other end is, well elsewhere....it is not in the SCM at all.

90% of the 1/4w resistors in there look like pure-dee-crap so I will swap them out, but I am using a 'replace with what you find' motif rather than 'RTFM' since the SCM is so very wrong.

Id be interested in hearing what you used for a dropping resistor across the Se rectifier. In other sets where I have done this that use the std 22ohm inrush limiter, I settle on a 120-150 ohm resistor given the higher line voltages. (and remove the 22 ohm to boot)

As part of my work I am using a polarized cord and rewiring to the switch to force the rectifier to be hot, that way chassis ground is at or near earth and not -125. Biggest issue I had to get over what I utterly assume is a schematic error where the diode symbol is drawn backwards, try as I might, there was no way I could work it out in my head where that circuit could ever work - if it did it would reverse the polarity across the filter caps.