[Sean]

Murf,

The wires on the transformer are colored as follows:

Primary: White, White
B+ Secondary: Yellow, Yellow-Red, Yellow
Filament: Black, Black
Rectifier Filament: Blue, Blue

I have attached a photo of the underside of a 42-1015 I recently restored. It should be similar to your 42-1012. I have marked 3 points that pertain to the power cord, power switch, and transformer primary connections. With the power off and the set unplugged push any of the push buttons other than the OFF button (left most button). Set your meter to read resistance.

Put one lead of your meter on the point marked "POWER CORD & POWER SWITCH". Put the other lead of your meter on the point marked "POWER SWITCH & TRANSFORMER PRIMARY (WHITE)". You should get a resistance reading of nearly 0 ohms. If you get a reading that is higher than a couple of ohms then you have a problem with the power switch.

If this checks out OK then move the lead of your meter from the "POWER CORD & POWER SWITCH" connection and place it on the "POWER CORD & TRANSFORMER PRIMARY (WHITE)" connection. Keep the other lead on the "POWER SWITCH & TRANSFORMER PRIMARY (WHITE)" connection. You should get a reading of a few ohms (around 3 to 5 ohms). If you get a much higher resistance reading here then the primary of your transformer is most likely open.