Dividohm Resistors

[passaloutre]

I work in a place where there is a small abundance of “vintage”electronic parts. It’s a hydraulics laboratory, where my job is building data logging systems that interface with various temperature/pressure/salinity sensors, flow meters, etc. back in the day a lot of these sensors were analog and we used to have technicians on hand to service them, but these days everything is digital and disposable. The technicians of yore left behind a lot of test equipment and an assortment of components. I’ve saved a couple oscilloscopes, a variac, and a lot of germanium transistors from the scrap pile, but a lot of the stuff is not immediately applicable to audio circuits.

Today I came across a stash of a a few dozen NOS Ohmite “Dividohm” resistors, specifically 50W 200 ohm variable resistors. Since I’m in the process of working on a cathode biased power amp, and I’ve read some recent threads on “adjustable cathode bias”, my first thought was these could be used to dial in the cathode bias. The amp I’m working on has a slightly cool bias with 200 ohm, so I figured these would be great for getting it exactly where I want.

 I’m just wondering if there’s anything to look out for with these. Do I need to be concerned about the inductance of the winding? Might they break down over time?

Sorry I know there’s a very ugly cable in the foreground, I promise it’s just for testing. I realized I didn’t have any better photos of the resistor, so I just used that one.

[PRR]

Nothing to worry about. These will NOT "break down over time", at least unto your grandchildren. (Or the next saltwater flood.)