[bikenepa]

I have been working on a Philco 40-115 which needed to have almost all the rubber wires replaced along with the capacitors,  it was  labor of love for sure.   I was pleased that it worked at all.  My question is does anyone worry about the modern line voltages on these AA5 Philco radios.  My line voltage is around 125 volts and if I add up all the tubes and the pilot light I just scrape in at 101 volts.  There is a filament dropping resistor candohm  that is dropping the voltage some.  I  did some voltage checks and the radio is running about 10 volts higher than the schematic voltages.  I measured these with a modern meter and an old analog Simpson and they are around the same.    

I have worried about the higher voltages with transformer based radios and do drop the voltage for those.   This radio will be returned to the original owner and I have no idea what kind of line voltages they will have.   

Thanks for reading!

[morzh]

Well...if it is a unit you intend to run long and often, then you could either increase the Candohm value, or you could use a bucking transformer. 9% up from the nominal will add roughly 0.6V per tube.

[35Z5]

You could always toss a 50A5 in it, that'd raise string voltage to approx 116v plus the candohm...

For octal sets I'm a fan of using 45Z5 in place of 35Z5, unfortunately Locktals don't have that option...

[Arran]

The resistances in the Candohm equals 185 Ohms total, the 53 ohm section is in parallel with a pilot lamp, at least on the code 121 version, and all the tubes have 150 ma filaments, so the drop across that resistor is 27.75 volts. The drop across the tube filaments is 95.2 volts, so 95.2+ 27.75= 122.95 volts. There are two things that you can do, first contact the power company and tell them that the line voltage is too high, your house should share a transformer with three or four others and it should be putting out 120 volts + or - 2 volts. The other option would be to add more resistance to make up for the extra two volts, so substitute the 132 ohm section for a 146 ohm resistor, or as close to it as possible so probably a 150 ohm unit, make sure you use something like a 10 Watt or higher if it will fit. I would not use a 50A5 in place of the 35A5, then you would end up with too much of a voltage drop, 15 volts more when you only need 2 volts more, if the dropping resistor stays in place.
Regards
Arran

[bikenepa]

thank you for the reply,  this was the information I was looking for.   the candohm seems to be in good shape and has drifted a bit higher so I was thinking it could stay in place.  I have replaced these before.  I have a stock of 10 watt resistors in the correct values to replace this one if need be.  As far as having the power company lower the voltage,  it is not happening that is the voltage being delivered in my area.  I am one of three on the transformer and I am on a first name basis with the power company as we have had dealing with interference in the past.  This radio is a restore for a kayaking friend of mine,  it belonged to her family.  I have no idea where it is actually going to be used but I believe it will be given to her son who lives in the  San Diego area (I live in Pennsylvania).  Not sure what the line voltage will be there.  If this was mine it would not be an issue since I run the old stuff on a bucking transformer.   really appreciate your helpful comments.

[morzh]

You'd be better off to not replace the candohm but adding to it. This way you need a smaller wattage resistor plus no woes of attaching it to the chassis for cooling. The addition will only dissipate a fraction of the power.