There Has to Be a Better Way.

[Winky Dink]

- I did try another 6A7.
- Shadow meter shows 2.5Kohms, which I believe is proper.
- I did hook up the signal meter and found max output at the IF frequency with no adjustment to transformers.

I will post the IF transformer voltages as soon as I can be sure I'm not posting spurious data--like mixing up primary and secondary.

Thanks
Winky

[Winky Dink]

The final score is 245 Volts on both ends of 1st IF transformer primary (and -2.5 Volts on the secondary).

[Winky Dink]

Reece, thanks for your attention to my issue. Tonight I started following circuits from the problem grids, pulling out components to test them out of the circuit, and looking closely at every solder joint.

Found a cap that may not have been grounded due to a rusty bolt. That fixed the voltage at the anode grid. Then, at 3:00 a.m., I found a resistor that tested OK out of the circuit but was apparently shorting under load. That fixed the oscillator grid.

The culprit:

[Winky Dink]

Curiosity overcame me this morning. The few carbon resistor failures that I've seen looked burned. Why would this normal-looking resistor fail? I assume this porosity wasn't part of the design, but was it a manufacturing defect or did it occur during use?



In that vein, here's a photo of something I found a few months ago when I started this project. When checking continuity, I couldn't get consistent readings on this coil. I think somebody at the factory forgot to solder this one.

[Reece]

It's all just circuit tracing. Good for you. So is the radio working OK now? You might want to go back through and look at all chassis grounds: they might look OK but have hidden corrosion that will show up later as intermittence or silence. What some do is grind a bit on the chassis right next to the grounding lug and with a heavy iron or gun get solder from the lug right over and onto the chassis.

[Reece]

We were posting at the same time! Wow, take a pic of that unsoldered lug and send it back to the Philco factory in Philly. They'll take proper measures.