[Guest]

Hello, I am new to tube radio restoration, but not to electronics. I recently acquired a Philco 76 Lowbay (Early Version). I have found the schematic on-line and have a question. All over the schematic are numbers in circles with an arrow pointing at various component components. What are the meaning of these numbers in circles?

Thanks,
Frank

[Raleigh]

Philco did not number components like modern electronics, with an R or C or other letter designating the kind of component, though some other manufacturers did at the time. Philco schematics usually numbered each component sequentially, increasing from the antenna on the left side of the schematic through to the speaker on the right side. Those numbers are shown with the number in a circle, often with an arrow pointing at the component. I'm not familiar with the schematic for your model 76, but that is what it is on all of the Philco schematics I've seen.

If you have the parts list, the part number and value of the component will be referenced by the same number. Likewise, the same number is used on the component location diagram.

The value of resistors and capacitors are usually also shown on the schematic, but usually not the voltage rating (for capacitors) or wattage ratings (for resistors.) A capacitor body usually, but not always, has its voltage rating written on it. You can often tell the wattage of the resistor by its size, but this is not a reliable way for all types or if you are unfamiliar with antique resistors. It is best to refer to the parts list.

Now, the parts list may or may not list the resistor wattage or capacitor voltage ratings directly. If it does not, you can look up the Philco part numbers on Chuck's site, here: http://www.philcorepairbench.com/partinfo.htm.

For resistors, you can usually derive the wattage from the part number, which is explained on this page on Ron's web site: http://www.philcoradio.com/tech/resistor.htm

Rather than use a schematic you find on line, which is likely to be incomplete or of poor quality, I'd advise you to buy a copy of the original Philco service data from Chuck Schwark at this site: http://www.philcorepairbench.com/schematics.htm. Chuck's copies are clear and complete. They are inexpensive and are an excellent value.

[Guest]

Hello John,

I was afraid that the circled numbers would point to a parts list. I will definitely get the Philco data from Chuck Schwark. Thanks for all of your assistance.

Cheers,
Frank