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Resistor questions (wattage and ohms) - Printable Version

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Resistor questions (wattage and ohms) - mrmurr2003 - 11-11-2019

So I am still working on my 38-12 and I am attacking some nasty looking resistors. I noticed alot of posts regarding what wattage and a link to Philco Bench but when I click on it I get an error that page could not be found. Is there another resource? Also, if I can't get the exact ohm rating for a resistor, can I go a bit higher or lower? Example: if the schematic calls for a 200 ohm resistor, can I use a 220? Thanks for helping with these questions. Also, in line with the wattage question, I am shopping for a kit with single wattage assortment of resistors and are there any recommendations on this?

RE: Resistor questions (wattage and ohms) - mikethedruid - 11-11-2019

You can always go higher in wattage than the original resistor, but you should try to match the specified resistance as closely as possible, or at most don't go more than 10% over or under. If the resistor is the old body-end dot type with no metallic color on the other end, it is 20% tolerance. If it has silver it is 10%, or gold is 5%. With resistors with bands the tolerances are the same, just 3 bands, 20%, a 4th band that is metallic colored means the same as the colors above. I buy modern 1% resistors of the proper resistance and rated higher in wattage. A modern metal film resistor that is 2 watts will be about the same size as an old 1/2 watt. I buy assortments of these on eBay in both 2 watt and 3 watt, which I use for 1/2 watt and 1 watt respectively, and then order specific resistances in 2 watt if I need to to get the ones I need that are not in the assortment. I also order specific resistances in higher wattage when needed, as when replacing those of a candohm. By the way, here is a horse to remember the resistor color code that I learned in the Navy many years ago, before women were allowed to be on ships, and before "political correctness"...
Bad        black        0
Boys      brown        1
Rape      red            2
Our        orange        3
Young    yellow        4
Girls        green          5
But        blue            6
Violet    violet            7
Gives      grey            8
Willingly  white          9
Get        gold            5%
Some    silver            10%
Now        none          20%

This is another horse we used to remember sine, cosine, and tangent when doing resonance and reactance problems...
                                Oscar (opposite)
Sally (sine)      =     ________
                                Has (hypotenuse)

                                 A (adjacent)
Can (cosine)   =      _________
                                Hard (hypotenuse)

                                On (opposite)
Tell (tangent)  =      _____________
                                Always (adjacent)

RE: Resistor questions (wattage and ohms) - mrmurr2003 - 11-11-2019

Good stuff. Thanks much for the input. I have several radios I am working on and was trying to consolidate my purchasing. This 38-12 I am working on has been "violated" previously and I am trying to bring it back to the original schematic.

RE: Resistor questions (wattage and ohms) - morzh - 11-11-2019

Yep, I learned the same mnemonics. I think it's the Navy one.