RMS Tahiti: set a distance record of 5,500 miles with Estevan.

Simpson Vacuum Tube Checker

  There was very little in the way of test equipment for a spark transmitter station. The wireless transmitter equipment, while physically large, was simple and came equipped with built in metering to monitor the diesel engine generator's voltage and current output, plus an ammeter in the antenna. The first receivers on the coast were magnetic detectors, so named because of the horseshoe shaped magnets comprising the bulk of the unit. These receivers were mechanical in nature and required the operator to wind the clockwork mechanism. These magnetic detectors were replaced by crystal receivers within months.  Crystal sets had no clockwork.  Screw drivers, pliers, wrenches and the like be the tools required to get an early station back on the air.

   The operators on the stations were trained to trouble shoot the equipment they operated and also had to demonstrate they were proficient in order to receive their operating licenses.

   The operators soon learned to listen to their transmitter's spark crackle. Many signs of an impending failure would be reflected in the sound of the spark. Trouble shooting would entail noting any irregularities in the readings of the supply voltage and current, or the current flowing in the antenna. Faults most likely would appear, as they still do in today's equipment, where ever there is heat or stress. High voltage transformers, the spark, and the capacitors would all be likely suspects. Many of the repairs could be made with simple tools and parts made from the operator's junk box.

   A tube checker, such as the Simpson Model 222 (late 1930's) in the photo, would test for these faults. Tube to be tested would be removed from the equipment, the checker's switches set as the Simpson handbook would specify for that particular tube, the tube inserted, and result seen on the meter in the middle of the instrument.

  This model checked for inter-electrode leakage, cathode emission and filament operation--a basic test.

   Wireless technology improved and by the early 1920's spark transmitters and associated receivers were being replaced by vacuum tube equipment. Servicing became a magnitude more difficult and specialty test equipment was required. Something to test the vacuum tubes was required. 


  Vacuum tubes could develop shorts/leakages between their internal elements, and more likely, a reduction in cathode emission.

Dayrad company's test set.
     In 1935 the Dayrad company produced this innovative test set.  A user would remove a suspect vacuum tube from the receiver, plug the tube into the Dayrad, and then plug the Dayrad into the receiver's empty socket.  By manipulating the various switches on the test set and monitoring the meter,  the user would see the tubes voltages and currents under actual operating conditons. User's manual available here.                  Statham collection
Dayrad Series 52 Checker
1935 advertisment for the Dayrad.