▼ Menu

    
Extras ▼

This exhibit is a thermal delay switch. Such delays were essential in series with the anode supplies to mercury vapour rectifiers as the rectifier could be ruined if the current flowed before the ionised gas was properly formed. The Operating parameters may be the figures on the label 28 V at 27.5 mA.

Physically this looks very much like Type 603, only in this case a base cap is present. The 603 dates to the early 1950's and probably this does as well but with a different delay time etc.

The filament strands pass round a top insulator and look to be held in tension by the spring.

The B4 Base.

Thanks to Mark Mallison for sending the images.

The wide glass tube envelope is  mm in diameter, and excluding the B4 base pins is  mm tall.

Reference: Observation.