[RodB]

So, I checked the schematic from Nostalgia Air and there is no way the symbols reflect the difference between standard capacitors and electrolytics. So you use experience and capacitor values to find the electrolytics. I see 3 electrolytics in the schematic, C16, 30 and 31. C16 negative is grounded to chassis and C30 and 31 negatives are connected to the power transformer center tap, which is the most negative point of the power supply, also known as B-. In tube radios of this era, the B+ and C- power supply are generated from the same source, the high voltage secondary winding of the power transformer. You'll see resistors R17 and 18 form a voltage divider connected between the center tap and ground. These create the negative C- bias voltages for the audio tubes.

You can also check the parts list and this one lists the capacitor values in ascending order. At the end of the list it shows 3 electrolytics. Sometimes the list will tell you what kind of capacitor is being used; mica, paper or electrolytic. If any doubt at this point you have us to contend with. Just ask.