Help with Resistor Wattage

11/20/2006 8:02:02 PMGeorge Matthis

Hi:

I'm working on an early 50's vintage chassis and can't seem to figure out the wattage of some of the resistors . They are longer than, but the same diameter, as the one watt resistors in the unit. I always thought that the diameter determines the wattage, not the length. Is there some rule of thumb, a website with pictures for examples etc that might help me?

PS - I have the schematic but it doesn't differentiate between resistor wattages, just gives resistance values.

Thanks in advance!
George

11/20/2006 8:10:53 PMDoug Criner

George, I would have thought that most resistors of '50s vinatage would be OK in tolerance. Whatever.

Often, you can estimate the max voltage across the resistor by inspecting the schematic, and calculate the wattage. Then double the wattage for rating the resistor, for good measure.

If you are uncertain, you can always jack up the wattage.

Hi:
:
:I'm working on an early 50's vintage chassis and can't seem to figure out the wattage of some of the resistors . They are longer than, but the same diameter, as the one watt resistors in the unit. I always thought that the diameter determines the wattage, not the length. Is there some rule of thumb, a website with pictures for examples etc that might help me?
:
:PS - I have the schematic but it doesn't differentiate between resistor wattages, just gives resistance values.
:
:Thanks in advance!
:George

11/20/2006 8:31:54 PMGeorge Matthis

Thanks Doug - I'm finding that the values for around 50% of the resistors are off by 15-20%. These are mostly 10% tolerance resistors and since I'm replacing the wax/paper and electrolytic caps anyway thought it a good idea to do a complete job.

:George, I would have thought that most resistors of '50s vinatage would be OK in tolerance. Whatever.
:
:Often, you can estimate the max voltage across the resistor by inspecting the schematic, and calculate the wattage. Then double the wattage for rating the resistor, for good measure.
:
:If you are uncertain, you can always jack up the wattage.
:
:Hi:
::
::I'm working on an early 50's vintage chassis and can't seem to figure out the wattage of some of the resistors . They are longer than, but the same diameter, as the one watt resistors in the unit. I always thought that the diameter determines the wattage, not the length. Is there some rule of thumb, a website with pictures for examples etc that might help me?
::
::PS - I have the schematic but it doesn't differentiate between resistor wattages, just gives resistance values.
::
::Thanks in advance!
::George