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Philco 2W resistors mystery - Printable Version

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RE: Philco 2W resistors mystery - Jamie - 05-20-2014

Quote:Kits are expensive.

if you know values you want, just make a list and go to Mouser.

Well, that's just it... I don't want to have to make a special order all the time. I like to have the replacements on hand. I usually try to buy in bulk, so I have a nice stock of parts that are ready to use. I have about 10 of every value resistor, but they are all 1/2w. Same with caps - I have most values. I have founds that the kits from Justradios are a good savings instead of buying one piece at a time. I just wish he offered a 2w kit too.

RE: Philco 2W resistors mystery - TA Forbes - 05-20-2014

Jamie: try justradios.com for your 2W resistors.

RE: Philco 2W resistors mystery - Raleigh - 05-24-2014

Years ago I bought the 1/2 watt kit from Radio Daze and the 1 watt kit from AES. I've occasionally put 2 or even 3 resistors in series when I need a larger wattage resistor than I have on hand. Unless the space is too tight, that usually works fine. I try to use values that are close if not the same, so I split the power more or less evenly.

By the way, Just Radios now offers 2W kits in metal oxide and carbon film types. They also have a 5 W wire wound kit.

I too like having the supplies on hand so I don't have to wait for an order to come it. It's nice to have 'em if I need 'em. I'm not sure the kits are really a good value, though, because there are many, many values I never use at all.

RE: Philco 2W resistors mystery - codefox1 - 05-26-2014

There is no guarantee that a very old component will perform as expected even under trivial loads regardless of careful storage. Some were not all that good on the day they were made. others have simply not aged gracefully. Sadly, few if any should be trusted for service in your home.

RE: Philco 2W resistors mystery - Joeztech - 06-01-2014

I agree with the recommendation to replace the resistors as a matter of course. I have seen carbon 2W resistors in B+ dropping service and/or plate load resistors that went down in value so far that they charred and caught on fire. Replace dropping resistors with metal types of correct or slightly higher wattage rating and rest easy. When you consider the time you are putting into getting the radio to work correctly and safely, new resistors are a good policy.

Joe

RE: Philco 2W resistors mystery - Arran - 06-01-2014

Body-end-dot code resistors, especially the dog bone style, are notorious for drifting upward in value. If you look at the construction they are basically a solid rod made out of a carbon composition material with a wire lead wrapped around either end. I think that the drifting may in part be the carbon composition and in part the contact between the leads and that rod building up resistance. Why some would drop in resistance could only be explained by the composition material becoming less resistive with age.
In the case of something like a Philco model 80 or 84 it's a four tube set, so every part that drifts or fails has that much more impact on the performance of the radio then in a set with a higher tube count. So I'm not surprised that replacing most of the resistors is necessary to get the set to work, there is just no redundancy in a 4 tube set. When these resistors were originally produced I believe that a a tolerance of + or - 20% was the norm, so the circuit could handle at least that much deviation, but + or - 50% or 100% no.
Regards
Arran