Hey all,

I heard about 4 pin F90T17 starters and wonder what is the point and how they are wired. Any info is appreciated.

They were originally thermal starters with the heating coil in series with the bulb and the bimetallic contacts wired where a typical 2 pin glowbottle starter would be wired. The thermal starters were desgined to easily start the F90T17 tubes, even in cold conditions. Later, glowbottle retrofits were made (some of which I own). These simply have a brass shorting strip wired in series with the bulb, and the glowbottle part wired where a 2 pin starter would normally be wired.
Hope this helps.   

They were originally thermal starters with the heating coil in series with the bulb and the bimetallic contacts wired where a typical 2 pin glowbottle starter would be wired. The thermal starters were desgined to easily start the F90T17 tubes, even in cold conditions. Later, glowbottle retrofits were made (some of which I own). These simply have a brass shorting strip wired in series with the bulb, and the glowbottle part wired where a 2 pin starter would normally be wired.
Hope this helps.   

Oh okay, Thank you! Wonder why the coil wasn't just a seperate part instead of being with the starter.

Oh okay, Thank you! Wonder why the coil wasn't just a seperate part instead of being with the starter.

Probably cheaper (and easier) to manufacture it that way.

Probably cheaper (and easier) to manufacture it that way.

But you would have to change it out every time you put in a new starter, maybe it wore out somehow.

I suspect that compatibility with 4 and 2 pin glowbottle starters may have also been a factor once those became the industry standard.